Class 9 NCERT Important Questions and Answers
Chapter 5 - The Fundamental Unit of Life 

Welcome to our AJs Chalo Seekhen. This webpage is dedicated to Class 9 Science Chapter 5 - The Fundamental Unit of Life. Here, you will find a comprehensive collection of important questions and answers that cover the key concepts and topics discussed in this chapter. Whether you're a student looking for exam preparation or a teacher seeking additional resources, our webpage provides a valuable resource to enhance your understanding of the fundamental unit of life, including cell structure, functions, and various types of cells. Dive into our carefully curated questions and answers to strengthen your knowledge and excel in your science studies.

NCERT Class 9 Science - Important Questions and Answers
Chapter 5 - The Fundamental Unit of Life 

1. Who discovered cells, and how?
   Cells were discovered by an English scientist named Robert Hooke in the year 1665. He used a microscope to examine a thin slice of cork and observed small compartments that he called "cells."
   
   
2. What did Robert Hooke observe in a thin slice of cork?
   Robert Hooke observed small compartments in a thin slice of cork, which he called "cells." These cells appeared like small empty rooms or chambers.


3. What is the composition of safranin solution used in the activity?
   The composition of safranin solution used in the activity typically consists of safranin dye dissolved in water or another suitable solvent. Safranin is a red-colored dye that stains certain cell structures, making them more visible under a microscope.


4. How did Robert Brown contribute to the study of cells?
   Robert Brown, a Scottish botanist, contributed to the study of cells by discovering and describing the cell nucleus in 1831. His observation of a dark, spherical structure within plant cells led to the identification of the nucleus as an essential component of cells.


5. What is the significance of the invention of magnifying lenses in the discovery of the microscopic world?
   The invention of magnifying lenses, particularly the compound microscope, played a crucial role in the discovery of the microscopic world. It allowed scientists to observe and study cells, microorganisms, and other tiny structures that were previously invisible to the naked eye, leading to significant advancements in the field of biology.


6. What are some examples of other unicellular organisms besides Amoeba, Chlamydomonas, Paramecium, and bacteria?
   Some examples of other unicellular organisms include Euglena, diatoms, yeast, Plasmodium (the causative agent of malaria), and Trypanosoma (causing African sleeping sickness).


7. How do cells in multicellular organisms differentiate to form different body parts?
   Cells in multicellular organisms differentiate through a process called cell specialization or cell differentiation. This process involves specific genes being activated or deactivated, leading to cells acquiring unique structures and functions that enable them to perform specialized tasks in different body parts.


8. What are some examples of cell organelles and their functions?
   Some examples of cell organelles and their functions are:
   • Nucleus: Controls cell activities and stores genetic information.
   • Mitochondria: Produces energy through cellular respiration.
   • Endoplasmic reticulum: Involved in protein synthesis and lipid metabolism.
   • Golgi apparatus: Modifies, packages, and transports proteins.
   • Lysosomes: Contain enzymes for intracellular digestion.
   • Chloroplasts: Found in plant cells, involved in photosynthesis.
   • Vacuoles: Store water, nutrients, and waste materials in plant cells.


9. How does the shape and size of a nerve cell differ from other types of cells?
   Nerve cells, also known as neurons, have a unique structure that allows them to transmit electrical signals throughout the body. They have long extensions called dendrites and axons, which can be much longer than the average cell size. This elongated shape helps nerve cells to establish connections with other cells over long distances.


10. How does the presence of organelles contribute to the complexity of a cell's structure?
    The presence of organelles in a cell contributes to its complexity by enabling specialized functions to be performed efficiently. Each organelle has specific roles and functions, allowing the cell to carry out a wide range of activities necessary for its survival and proper functioning.
    
    
    
    
11. What is the role of the plasma membrane in a cell?
    The plasma membrane, also known as the cell membrane, surrounds the cell and acts as a protective barrier. It regulates the movement of substances in and out of the cell, allowing nutrients to enter and waste products to exit. The plasma membrane also plays a role in cell signaling and communication with the external environment.


12. How does the cytoplasm contribute to cell metabolism?
    The cytoplasm is a jelly-like substance that fills the cell and houses various cellular structures. It plays a vital role in cell metabolism by providing a medium for chemical reactions to occur. Many metabolic processes, such as protein synthesis and energy production, take place within the cytoplasm.
    
    
    


13. Can cells perform functions independently, or do they rely on other cells?
    Cells can perform various functions independently, especially in unicellular organisms. However, in multicellular organisms, cells often specialize and work together in a coordinated manner to perform complex tasks and maintain the overall functioning of the organism.


14. How do cells adapt to different environments and perform specialized functions?
    Cells adapt to different environments and perform specialized functions through a process called cell differentiation. During development, cells receive signals that activate specific genes, leading to the development of specialized structures and functions necessary for their specific roles in the organism.


15. How did Leeuwenhoek contribute to the study of cells?
    Antonie van Leeuwenhoek, a Dutch scientist, made significant contributions to the study of cells by improving the design of the microscope and making detailed observations of various microscopic organisms, including bacteria, protozoa, and red blood cells. He is often referred to as the "Father of Microbiology."


16. Who coined the term "protoplasm" for the fluid substance of the cell?
    The term "protoplasm" for the fluid substance of the cell was coined by a German physiologist and anatomist named Hugo von Mohl in the year 1846.


17. How did Virchow expand the cell theory?
    Rudolf Virchow, a German physician and pathologist, expanded the cell theory by proposing that all cells arise from pre-existing cells. This concept, known as cell division, contradicted the earlier belief that cells can spontaneously generate.


18. What led to the discovery of the microscopic world?
    The invention and improvement of the microscope, along with the curiosity and observation of scientists like Robert Hooke and Antonie van Leeuwenhoek, led to the discovery of the microscopic world. The microscope allowed scientists to explore and study the intricate structures and organisms that were previously unseen.


19. How does the shape of an Amoeba cell differ from other cells?
    Amoeba cells have a unique shape known as an amoeboid shape. They are characterized by their constantly changing, irregularly shaped extensions called pseudopodia, which they use for movement and capturing food particles.


20. What are the basic functions performed by all living cells?
    All living cells perform basic functions such as:
    • Obtaining and utilizing energy.
    • Synthesizing proteins and other essential molecules.
    • Replicating genetic material.
    • Responding to stimuli from the environment.
    • Maintaining homeostasis.
    • Growing and developing.
    • Eliminating waste products.




21. How is division of labor seen within a single cell?
    Division of labor within a single cell is seen through the presence of different organelles, each with specific roles and functions. Just like different workers in an organization have specific tasks, organelles in a cell work together harmoniously, with each organelle carrying out a specialized function necessary for the cell's overall functioning.


22. What is the role of cell organelles in cell functioning?
    Cell organelles play vital roles in cell functioning by carrying out specific functions necessary for the cell's survival and proper operation. For example, the nucleus stores genetic information, mitochondria produce energy, and the endoplasmic reticulum is involved in protein synthesis.


23. Can the structure of a cell determine its function?
    Yes, the structure of a cell is closely related to its function. Different cells have unique structures that enable them to perform specific functions efficiently. For example, muscle cells have elongated fibers that allow them to contract, while nerve cells have long extensions to transmit electrical signals.


24. What are some examples of specialized cells in multicellular organisms?
    Some examples of specialized cells in multicellular organisms include:
    • Red blood cells (erythrocytes) for oxygen transport.
    • Muscle cells for contraction and movement.
    • Neurons for transmitting electrical signals.
    • Epithelial cells for lining surfaces and protection.
    • Xylem and phloem cells for transporting water and nutrients in plants.


25. How does the interaction between a cell and its environment occur?
    The interaction between a cell and its environment occurs through the plasma membrane. The plasma membrane allows selective movement of substances, such as nutrients and waste products, between the cell and its surroundings. Cell signaling and communication with the external environment also occur through specific receptors on the plasma membrane.


26. What are the components of a cell's plasma membrane?
    The components of a cell's plasma membrane include lipids (phospholipids, cholesterol), proteins (integral proteins, peripheral proteins), and carbohydrates (glycolipids, glycoproteins). These components work together to form a selectively permeable barrier that controls the movement of substances in and out of the cell.


27. What is the role of the nucleus in a cell?
    The nucleus is the control center of the cell. It stores the cell's genetic material (DNA), which contains instructions for the cell's functioning and development. The nucleus regulates gene expression and controls the synthesis of proteins necessary for various cellular processes.


28. What is cytoplasm, and what does it contain?
    Cytoplasm is a gel-like substance that fills the cell between the nucleus and the plasma membrane. It contains various cellular structures, including organelles like mitochondria, endoplasmic reticulum, and Golgi apparatus, as well as dissolved nutrients, ions, enzymes, and other molecules necessary for cell metabolism.


29. Are there any exceptions to the presence of organelles in cells?
    Yes, there are exceptions to the presence of organelles in cells. Red blood cells in mammals, for example, lack a nucleus and most other organelles to maximize space for oxygen transport. However, most other types of cells in the body contain organelles necessary for their specific functions.
    


30. How does the organization of a cell contribute to its overall structure and function?
    The organization of a cell, including the arrangement and interactions of its organelles and structures, contributes to its overall structure and function. Each organelle has a specific role, and their coordinated functioning allows the cell to carry out essential processes efficiently, leading to its overall structure and function.


31. How do cells maintain homeostasis?
    Cells maintain homeostasis by regulating various internal factors such as temperature, pH, and nutrient levels. They use mechanisms like feedback loops and transport proteins in the plasma membrane to balance and adjust these factors to ensure optimal cellular function and stability.


32. What are the differences between plant and animal cells?
    Plant and animal cells have several differences:
    • Plant cells have a rigid cell wall, while animal cells do not.
    • Plant cells have chloroplasts for photosynthesis, while animal cells do not.
    • Plant cells typically have large central vacuoles, while animal cells have smaller or no vacuoles.
    • Plant cells can have plasmodesmata for communication between cells, while animal cells rely on direct contact or chemical signaling.


33. How do cells communicate with each other?
    Cells communicate with each other through various mechanisms, including chemical signaling. Signaling molecules, such as hormones and neurotransmitters, are released by one cell and detected by specific receptors on the target cell's plasma membrane. This communication allows coordination and cooperation between cells in multicellular organisms.


34. What is the role of mitochondria in cellular energy production?
    Mitochondria are often called the "powerhouses" of the cell because their main function is to produce energy in the form of ATP (adenosine triphosphate) through a process called cellular respiration. They convert nutrients, such as glucose, into ATP, which is used by the cell for various energy-requiring activities.


35. Who discovered cells, and how?
    Cells were discovered by an English scientist named Robert Hooke in the year 1665. He used a microscope to examine a thin slice of cork and observed small compartments that he called "cells."


36. Why is the cell called the structural and functional unit of life?
    The cell is called the structural and functional unit of life because it is the smallest and most basic unit of living organisms. All living organisms are composed of one or more cells, and cells carry out essential functions necessary for life, such as obtaining energy, reproducing, and responding to the environment.


37. What did Robert Hooke observe in a thin slice of cork?
    Robert Hooke observed small compartments in a thin slice of cork, which he called "cells." These cells appeared like small empty rooms or chambers.


38. What is the origin of the word "cell" in biology?
    The word "cell" in biology comes from the Latin word "cellula," which means "small room" or "small chamber." Robert Hooke named these compartments he observed in cork cells due to their resemblance to small rooms or monks' living quarters.


39. What is the significance of Hooke's observation in the history of science?
    Hooke's observation of cells in cork was a groundbreaking discovery that revolutionized our understanding of the natural world. It provided evidence for the existence of a microscopic realm and laid the foundation for the field of cell biology, leading to further advancements in scientific knowledge and discoveries.


40. What is the composition of cork, and where does it come from?
    Cork is a material derived from the bark of cork oak trees (Quercus suber). It is composed of cells with thick cell walls, which contain a substance called suberin. The unique structure of cork cells, with their air-filled spaces, provides it with properties such as buoyancy and resistance to moisture and decay.
    
    



41. What activity can be performed with an onion peel under a microscope?
    With an onion peel under a microscope, you can observe and study the structure of plant cells. The transparent nature of onion epidermal cells allows for the visualization of various cell components, such as the cell wall, nucleus, and cytoplasmic streaming.


42. How can a temporary mount of an onion peel be prepared?
    To prepare a temporary mount of an onion peel, you can follow these steps:
    • Peel off a thin layer of the epidermis from the onion bulb.
    • Place the peel on a clean glass slide.
    • Add a few drops of water to the peel to prevent it from drying out.
    • Gently lower a coverslip onto the peel, avoiding air bubbles.
    • Press lightly to flatten the peel and remove excess water or air.
    • Secure the coverslip with clips or adhesive if necessary.
    • The temporary mount is now ready to be observed under a microscope.


43. What are the components of a compound microscope?
    The components of a compound microscope typically include:
    • Eyepiece or ocular lens for viewing.
    • Objective lenses of different magnifications.
    • Stage for placing the specimen.
    • Coarse and fine adjustment knobs for focusing.
    • Condenser lens to focus light onto the specimen.
    • Light source, such as a lamp, to illuminate the specimen.


44. What is the magnification of a microscope?
    The magnification of a microscope refers to how much larger the image of a specimen appears compared to its actual size. It is determined by the combination of the objective lens magnification and the eyepiece lens magnification. For example, if the objective lens has a magnification of 40x and the eyepiece lens has a magnification of 10x, the total magnification would be 400x.


45. Why is staining used in microscopy?
    Staining is used in microscopy to enhance the visibility of certain structures or components within cells or tissues. Stains, such as safranin or methylene blue, bind to specific cellular structures, highlighting them and making them easier to observe under the microscope.


46. How did Robert Brown contribute to the study of cells?
    Robert Brown, a Scottish botanist, contributed to the study of cells by discovering and describing the cell nucleus in 1831. His observation of a dark, spherical structure within plant cells led to the identification of the nucleus as an essential component of cells.


47. What is the function of the nucleus in a cell?
    The nucleus is the control center of the cell and performs several functions:
    • It stores the cell's genetic material (DNA).
    • It regulates gene expression and protein synthesis.
    • It controls the cell's growth, development, and reproduction.
    • It is involved in the transmission of genetic information to daughter cells during cell division.


48. What is the role of the cell wall in plant cells?
    The cell wall is a rigid outer layer found in plant cells, bacteria, fungi, and some protists. Its main functions are:
    • Providing structural support and shape to the cell.
    • Protecting the cell from mechanical stress and pathogens.
    • Regulating the movement of substances in and out of the cell.


49. What is the role of the chloroplast in plant cells?
    The chloroplast is an organelle found in plant cells and some protists. Its main role is to carry out photosynthesis, the process by which sunlight is converted into chemical energy (glucose). Chloroplasts contain chlorophyll, a pigment that captures sunlight, enabling plants to produce food and release oxygen.


50. What is the function of the vacuole in plant cells?
    The vacuole is a large, fluid-filled organelle found in plant cells. Its functions include:
    • Storing water, nutrients, and waste products.
    • Maintaining turgor pressure to provide structural support.
    • Controlling cell size and regulating cellular processes.
    • Participating in detoxification and pigmentation in some plant cells.



51. What are the differences between prokaryotic and eukaryotic cells?
    Prokaryotic cells and eukaryotic cells have several differences:
    • Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus.
    • Prokaryotic cells are typically smaller and simpler in structure.
    • Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells have various membrane-bound organelles.
    • Prokaryotic cells include bacteria and archaea, while eukaryotic cells are found in organisms such as plants, animals, fungi, and protists.


52. What are the three main parts of the cell theory?
    The three main parts of the cell theory are:
    • All living organisms are composed of one or more cells.
    • The cell is the basic unit of structure and function in living organisms.
    • All cells arise from pre-existing cells through cell division.


53. What is the function of ribosomes in a cell?
    Ribosomes are cellular structures responsible for protein synthesis. They read the instructions encoded in messenger RNA (mRNA) and link amino acids together to form proteins. Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum.


54. How does the endoplasmic reticulum contribute to protein synthesis?
    The endoplasmic reticulum (ER) is involved in protein synthesis and processing. It consists of a network of interconnected membranes. The rough endoplasmic reticulum (RER) has ribosomes attached to its surface, where proteins are synthesized. The smooth endoplasmic reticulum (SER) is involved in lipid metabolism, detoxification, and calcium storage.


55. What is the Golgi apparatus, and what is its role in the cell?
    The Golgi apparatus is an organelle involved in the processing, modification, and packaging of proteins and lipids. It consists of a series of flattened membranes called cisternae. The Golgi apparatus receives proteins from the endoplasmic reticulum, modifies them, and sorts them into vesicles for transport to their final destinations within the cell or outside of it.


56. What are lysosomes, and what is their function in cells?
    Lysosomes are membrane-bound organelles that contain digestive enzymes. They play a crucial role in the breakdown and recycling of cellular waste materials, damaged organelles, and foreign substances. Lysosomes fuse with these materials, breaking them down into smaller components that can be reused by the cell.


57. What is the significance of the discovery of cells for biology?
    The discovery of cells is of immense significance to biology as it laid the foundation for our understanding of the fundamental unit of life. It opened up avenues for studying and exploring the complex structures, functions, and processes that occur within cells. The cell theory, based on this discovery, provides a framework for understanding all living organisms and their interactions with the environment.
    
    
58. What is the main function of the plasma membrane in a cell?
    The main function of the plasma membrane is to separate the contents of the cell from its external environment, control the entry and exit of substances, and maintain the cell's internal environment.


59. How does the plasma membrane allow selective movement of substances?
    The plasma membrane has selective permeability, meaning it allows certain substances to enter and exit the cell while restricting the movement of others. This selectivity is determined by the size, charge, and solubility of the substances.


60. What is diffusion, and how does it contribute to the movement of substances into and out of the cell?
    Diffusion is the spontaneous movement of substances from an area of higher concentration to an area of lower concentration. It plays a crucial role in the movement of gases like carbon dioxide and oxygen, as well as other small molecules, into and out of the cell.




61. What is osmosis, and how does it differ from diffusion?
    Osmosis is the movement of water molecules across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration. While diffusion involves the movement of solute particles, osmosis specifically refers to the movement of water.


62. How does osmosis contribute to the movement of water in and out of the cell?
    Osmosis allows the movement of water across the plasma membrane to equalize the concentration of solute particles inside and outside the cell. If the external solution is hypotonic (lower solute concentration), water enters the cell, and if the external solution is hypertonic (higher solute concentration), water exits the cell.


63. What are the three possible outcomes when placing a cell in different types of solutions?
    When placing a cell in different types of solutions, three outcomes are possible: swelling or gaining water in a hypotonic solution, maintaining the same size in an isotonic solution, and shrinking or losing water in a hypertonic solution.


64. What is plasmolysis, and how does it occur in plant cells?
    Plasmolysis is the process in which a plant cell shrinks and pulls away from the cell wall due to water loss in a hypertonic solution. The cell membrane detaches from the cell wall, resulting in the contraction of the cell's contents.


65. What is the role of the cell wall in plasmolysis?
    The cell wall provides structural support and prevents the complete collapse of the cell during plasmolysis. It exerts outward pressure on the shrunken cell, helping maintain the integrity of the cell structure.


66. How does plasmolysis demonstrate the role of the cell wall in plant cells?
    Plasmolysis demonstrates that the cell wall allows plant cells to withstand hypertonic external environments without bursting. The cell wall counteracts the inward movement of water during osmosis, maintaining the cell's shape and preventing lysis.


67. What is the composition of the cell wall in plant cells?
    The cell wall in plant cells is primarily composed of cellulose, a complex carbohydrate that provides rigidity and strength to the cell. It also contains other substances such as hemicellulose, lignin, and pectin, depending on the cell type.


68. What is the significance of cellulose in the cell wall?
    Cellulose, the main component of the cell wall, provides structural strength and rigidity to plant cells. It allows plants to maintain their shape and provides support for the plant's overall structure.


69. What happens to an egg when placed in pure water?
    When an egg is placed in pure water, it swells due to the process of osmosis. Water molecules move from the area of higher concentration (water) outside the egg to the area of lower concentration (egg), causing the egg to increase in size.


70. What happens to an egg when placed in a concentrated salt solution?
    When an egg is placed in a concentrated salt solution, it shrinks. Water molecules move from the area of higher concentration (egg) to the area of lower concentration (salt solution), resulting in the loss of water from the egg.


71. How can the process of osmosis be observed using dried raisins or apricots?
    Dried raisins or apricots can be placed in plain water, causing them to gain water and swell. However, when placed in a concentrated solution of sugar or salt, they lose water and shrink. These observations demonstrate the effects of osmosis on dried fruits.


72. Which organisms tend to gain water through osmosis, and why?
    Unicellular freshwater organisms and most plant cells tend to gain water through osmosis. This is because they are usually surrounded by hypotonic environments where the solute concentration outside the cell is lower than inside. Water moves into the cell to balance the concentration gradient.


73. What is endocytosis, and how does it enable a cell to obtain food and other materials?
    Endocytosis is a cellular process in which the cell membrane engulfs external material and forms a vesicle around it. This process allows the cell to internalize and absorb food, nutrients, and other materials from its external environment.


74. Give an example of an organism that acquires its food through endocytosis.
    Amoeba is an example of an organism that acquires its food through endocytosis. It extends its pseudopodia around food particles, encloses them within vesicles, and brings them into the cell for digestion.


75. What are lipids and proteins, and what is their role in the structure of the plasma membrane?
    Lipids and proteins are organic molecules present in the structure of the plasma membrane. Lipids, such as phospholipids, form a lipid bilayer that gives the membrane flexibility and acts as a barrier. Proteins are embedded in the lipid bilayer and serve various functions, including transport, signaling, and structural support.


76. Why can the structure of the plasma membrane only be observed through an electron microscope?
    The structure of the plasma membrane is extremely thin and not visible under an ordinary light microscope. An electron microscope, which uses a beam of electrons instead of light, has higher resolution and can reveal the detailed structure of the plasma membrane.


77. What is the significance of electron microscopes in studying cellular structures?
    Electron microscopes allow scientists to study cellular structures with much higher resolution than traditional light microscopes. They provide detailed images of cell organelles, membranes, and other subcellular components, enabling a better understanding of cellular organization and function.


78. What is the significance of chloroplasts in plant cells?
    Chloroplasts are organelles found in plant cells that contain chlorophyll, the pigment responsible for photosynthesis. They capture sunlight energy and convert it into chemical energy, playing a crucial role in the production of glucose and oxygen during photosynthesis.


79. What is the purpose of mounting a Rhoeo leaf peel in water on a slide during the plasmolysis activity?
    Mounting a Rhoeo leaf peel in water on a slide allows for microscopic examination of the cells. It helps in observing the presence of chloroplasts and noting their distribution within the cells.
    
    
    
    
80. What happens to the cells of a Rhoeo leaf when a strong solution of sugar or salt is applied?
    When a strong solution of sugar or salt is applied to the cells of a Rhoeo leaf, plasmolysis occurs. The cells lose water due to the higher concentration of solutes in the external solution, causing the cell contents to shrink away from the cell wall.


81. What does the occurrence of plasmolysis in living cells indicate?
    The occurrence of plasmolysis in living cells suggests that only living cells are capable of absorbing water by osmosis. Dead cells do not exhibit plasmolysis since they lack the metabolic processes necessary for osmotic water uptake.


82. Why can plant cells withstand hypotonic external environments better than animal cells?
    Plant cells can withstand hypotonic external environments better than animal cells due to the presence of a rigid cell wall. The cell wall prevents excessive water intake and expansion, exerting equal pressure against the swollen cell to maintain its shape and prevent bursting.


83. What is the role of the cell wall in plant cells' ability to withstand changes in the surrounding medium?
    The cell wall provides structural support and strength to plant cells, allowing them to withstand greater changes in the surrounding medium compared to animal cells. It prevents the cell from bursting or collapsing under osmotic pressure changes.


84. What are the components of the cell wall in addition to cellulose?
    In addition to cellulose, the cell wall may contain other components such as hemicellulose, lignin, and pectin. These substances contribute to the mechanical strength and integrity of the cell wall, providing additional support and protection.


85. What is the role of hemicellulose in the cell wall?
    Hemicellulose is a complex carbohydrate found in the cell wall. It provides flexibility and elasticity, allowing the cell wall to withstand mechanical stress while maintaining its overall structure.


86. What is lignin, and what is its significance in the cell wall?
    Lignin is a complex polymer that provides rigidity and waterproofing to the cell wall. It strengthens the cell wall and makes it impermeable to water and other substances, enhancing the structural integrity of plant cells.


87. What is pectin, and what is its function in the cell wall?
    Pectin is a polysaccharide present in the cell wall that acts as a cementing substance, binding adjacent plant cells together. It helps maintain the overall structure of plant tissues and provides support for cell-to-cell adhesion.


88. What are the observable effects of plasmolysis on a Rhoeo leaf peel mounted on a slide?
    When plasmolysis occurs in a Rhoeo leaf peel, the cells shrink and move away from the cell wall. This can be observed under a microscope, where the presence of gaps between the cells and the cell wall indicates the occurrence of plasmolysis.


89. What conclusion can be drawn from the observation that plasmolysis only occurs in living cells?
    The observation that plasmolysis occurs only in living cells suggests that living cells have the ability to actively regulate osmosis and respond to changes in solute concentration. Dead cells lack the necessary cellular processes and metabolic activity required for plasmolysis.


90. What are the advantages of plant cells having a cell wall compared to animal cells?
    The presence of a cell wall in plant cells provides several advantages. It provides structural support, allows plants to grow upright, protects against mechanical damage, prevents cell rupture under osmotic pressure changes, and offers defense against pathogens.


91. What is the role of the nucleus in a cell?
    The nucleus is the control center of the cell. It contains the cell's DNA, which carries genetic information, and regulates the cell's activities, including growth, metabolism, and reproduction. The nucleus also directs the synthesis of proteins necessary for cell function.


92. What is the function of the nuclear membrane or nuclear envelope?
    The nuclear membrane or nuclear envelope surrounds the nucleus and separates its contents from the cytoplasm. It acts as a selective barrier, controlling the movement of substances between the nucleus and the cytoplasm, ensuring the integrity and security of the genetic material.


93. What is the significance of the nucleolus in the nucleus?
    The nucleolus is a substructure within the nucleus involved in the synthesis and assembly of ribosomes, which are responsible for protein synthesis. It plays a crucial role in the production of ribosomal RNA (rRNA) and the assembly of ribosomal subunits.


94. What is the purpose of the rough endoplasmic reticulum (ER) in the cell?
    The rough endoplasmic reticulum (ER) is involved in the synthesis, folding, and modification of proteins. It is covered in ribosomes, giving it a rough appearance, and serves as a site for protein synthesis and initial processing.


95. How does the smooth endoplasmic reticulum (ER) differ from the rough ER in terms of structure and function?
    The smooth endoplasmic reticulum (ER) lacks ribosomes on its surface, giving it a smooth appearance. It is involved in lipid metabolism, detoxification of drugs and toxins, and the storage and release of calcium ions. It plays a role in the synthesis of lipids, including phospholipids and steroids.


96. What is the role of the Golgi apparatus in the cell?
    The Golgi apparatus is involved in modifying, sorting, and packaging proteins and lipids for transport to their final destinations within or outside the cell. It receives vesicles from the endoplasmic reticulum and modifies their contents before sending them to their appropriate target locations.


97. What is the function of lysosomes in the cell?
    Lysosomes are organelles responsible for intracellular digestion and recycling. They contain enzymes that break down waste materials, cellular debris, and foreign substances. Lysosomes also play a role in programmed cell death (apoptosis) and the removal of damaged organelles.


98. What is the function of the mitochondria in the cell?
    Mitochondria are often referred to as the "powerhouses" of the cell because they generate most of the cell's energy through the process of cellular respiration. They produce adenosine triphosphate (ATP), the molecule used for energy storage and utilization in cellular processes.


99. What is the endosymbiotic theory, and how does it explain the origin of mitochondria?
    The endosymbiotic theory proposes that mitochondria were once free-living bacteria that were engulfed by ancestral eukaryotic cells and established a symbiotic relationship. Over time, the host cell and the ingested bacteria formed a mutually beneficial association, with the bacteria providing energy through respiration, and the host cell offering protection and nutrients.


100. What is the function of the cytoskeleton in the cell?
     The cytoskeleton provides structural support, maintains cell shape, and facilitates cell movement. It consists of protein filaments, including microtubules, microfilaments, and intermediate filaments, which help organize cell structures, enable intracellular transport, and contribute to cell division.




101. What is the significance of microtubules in cell division?
     Microtubules play a vital role in cell division by forming the mitotic spindle, a structure essential for separating replicated chromosomes during mitosis and meiosis. They guide the movement of chromosomes and ensure their correct distribution to daughter cells.


102. What is the function of microfilaments in cell movement?
     Microfilaments, primarily composed of the protein actin, are involved in cell movement and contraction. They enable cellular processes such as amoeboid movement, muscle contraction, and cytokinesis (division of the cytoplasm) during cell division.


103. What is the purpose of intermediate filaments in the cell?
     Intermediate filaments provide mechanical strength and support to cells. They help maintain cell shape and integrity, anchor organelles in place, and contribute to the structural stability of tissues subjected to mechanical stress, such as skin and muscles.


104. What is the role of peroxisomes in the cell?
     Peroxisomes are involved in various metabolic processes, including the breakdown of fatty acids, detoxification of harmful substances, and the production and breakdown of hydrogen peroxide. They contain enzymes necessary for these metabolic reactions.


105. What is the function of centrioles in animal cells?
     Centrioles are cylindrical structures involved in cell division. They play a crucial role in organizing the microtubules of the mitotic spindle during cell division and are responsible for the formation of cilia and flagella in some cell types.


106. What is the purpose of vesicles in the cell?
     Vesicles are small membrane-bound sacs involved in the transport, storage, and secretion of cellular materials. They can transport proteins, lipids, and other molecules between different organelles and to the cell membrane for secretion.


107. What is the function of the central vacuole in plant cells?
     The central vacuole in plant cells serves various functions, including maintaining turgor pressure, storing water, nutrients, and pigments, regulating ion concentrations, and contributing to cell expansion and growth. It is the largest organelle in plant cells and plays a critical role in maintaining cell rigidity and shape.
     
     
108. What is the process called when water molecules move across a selectively permeable membrane?
     The process is called osmosis.


109. What happens when an animal cell or a plant cell is placed in a hypotonic solution?
     The cell gains water by osmosis, causing it to swell up.


110. What is an isotonic solution, and what happens to a cell when placed in it?
     An isotonic solution has the same water concentration as the cell. When a cell is placed in an isotonic solution, there is no net movement of water across the cell membrane, and the cell stays the same size.


111. What happens to a cell when placed in a hypertonic solution?
     In a hypertonic solution, which has a lower concentration of water than the cell, the cell loses water by osmosis. As a result, the cell shrinks.


112. What is the process of endocytosis?
     Endocytosis is a process in which the cell membrane engulfs and takes in food particles or other materials from its external environment.


113. What is plasmolysis, and how can it be observed?
     Plasmolysis is the phenomenon of shrinkage or contraction of a plant cell's contents away from the cell wall when water is lost through osmosis. It can be observed by placing a de-shelled Rhoeo leaf in a strong solution of sugar or salt and observing the cells under a microscope.


114. What role do cell walls play in plant, fungal, and bacterial cells?
     Cell walls provide structural strength and allow these cells to withstand very dilute (hypotonic) external media without bursting. They help cells maintain their shape and provide protection.


115. Why did we put iodine solution on the temporary mount of onion peel?
     We put iodine solution on the temporary mount of onion peel to observe the presence of starch in the cells. Iodine reacts with starch and turns it blue-black in color.


116. What would we see if we tried observing the onion peel without putting the iodine solution?
     Without iodine solution, we would not be able to observe the starch granules in the cells. The cells would appear colorless or transparent.


117. Did each cell get evenly colored when we put iodine solution on the onion peel?
     No, each cell did not get evenly colored. Different regions of the cells got colored differentially due to their chemical composition. Some regions appeared darker than others.


118. Apart from iodine solution, what other solutions could we use to stain the cells?
     Apart from iodine solution, we could also use safranin solution or methylene blue solution to stain the cells.


119. What activity can we perform to observe cells from our own body?
     We can perform an activity that involves gently scraping the inside surface of the cheek with an ice-cream spoon, transferring the material onto a glass slide, and observing it under a microscope.


120. Does any material get stuck on the spoon when we scrape the inside surface of the cheek?
     Yes, when we scrape the inside surface of the cheek, some material gets stuck on the spoon.




121. How can we color the material scraped from the cheek for observation under a microscope?
     To color the material, we can put a drop of methylene blue solution on it.


122. What should we not forget to do when preparing the material for observation under a microscope?
     We should not forget to put a cover-slip on the glass slide containing the material.


123. What shape are the cells we see when observing the material from the cheek?
     The cells observed from the cheek are typically flat and irregularly shaped.


124. Was there a darkly colored, spherical or oval, dot-like structure near the center of each cell?
     Yes, there was a darkly colored, spherical or oval, dot-like structure near the center of each cell.


125. Were there similar structures in onion peel cells?
     Yes, there were similar structures (nuclei) in onion peel cells.


126. What is the double-layered covering around the nucleus called?
     The double-layered covering around the nucleus is called the nuclear membrane.


127. What is the function of the nuclear membrane?
     The nuclear membrane contains pores that allow the transfer of materials between the nucleus and the cytoplasm.


128. What do chromosomes contain?
     Chromosomes contain DNA (Deoxyribo Nucleic Acid) molecules.


129. When are chromosomes visible as rod-shaped structures?
     Chromosomes are visible as rod-shaped structures only when the cell is about to divide.


130. What is the composition of chromosomes?
     Chromosomes are composed of DNA and protein.


131. What is the role of DNA in chromosomes?
     DNA molecules contain the information necessary for constructing and organizing cells. They carry genetic information.


132. What are the functional segments of DNA called?
     Functional segments of DNA are called genes.


133. How is DNA present in a non-dividing cell?
     In a cell that is not dividing, DNA is present as part of chromatin material.


134. What does chromatin material look like?
     Chromatin material appears as an entangled mass of thread-like structures.


135. What role does the nucleus play in cellular reproduction?
     The nucleus plays a central role in cellular reproduction, which is the process by which a single cell divides and forms two new cells.


136. What other role does the nucleus play in a cell?
     The nucleus also plays a crucial part, along with the environment, in determining the way the cell will develop and what form it will exhibit at maturity, by directing the chemical activities of the cell.


137. What is the term for the nuclear region in prokaryotic cells?
     The nuclear region in prokaryotic cells is called a nucleoid.


138. What are organisms called whose cells lack a nuclear membrane?
     Organisms whose cells lack a nuclear membrane are called prokaryotes.


139. What are organisms called that have cells with a nuclear membrane?
     Organisms with cells having a nuclear membrane are called eukaryotes.


140. What are the other cytoplasmic organelles absent in prokaryotic cells?
     Prokaryotic cells lack most of the other cytoplasmic organelles present in eukaryotic cells.




141. What is the association of chlorophyll in photosynthetic prokaryotic bacteria?
     In photosynthetic prokaryotic bacteria, chlorophyll is associated with membranous vesicles (bag-like structures) rather than plastids as in eukaryotic cells.


142. Name some of the cell organelles we will discuss.
     Some of the cell organelles we will discuss are endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, and plastids.


143. What is the endoplasmic reticulum (ER)?
     The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets within the cell.


144. What are the two types of endoplasmic reticulum (ER)?
     The two types of endoplasmic reticulum are rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).


145. What gives the rough endoplasmic reticulum its rough appearance?
     The rough endoplasmic reticulum (RER) has particles called ribosomes attached to its surface, which give it a rough appearance.


146. What is the function of ribosomes in the cell?
     Ribosomes are the sites of protein manufacture in the cell.


147. What does the smooth endoplasmic reticulum (SER) help in manufacturing?
     The smooth endoplasmic reticulum (SER) helps in the manufacture of fat molecules or lipids, which are important for cell function.


148. What does the smooth endoplasmic reticulum (SER) contribute to?
     The smooth endoplasmic reticulum (SER) contributes to membrane biogenesis, the process of building the cell membrane.


149. What are some functions of proteins and lipids produced by the endoplasmic reticulum?
     Proteins and lipids produced by the endoplasmic reticulum can function as enzymes, hormones, and help in building the cell membrane.


150. What is the function of the endoplasmic reticulum (ER) in the cytoplasm?
     The endoplasmic reticulum (ER) serves as channels for the transport of materials, especially proteins, between various regions of the cytoplasm or between the cytoplasm and the nucleus.


151. What does the Golgi apparatus consist of?
     The Golgi apparatus consists of a stack of flattened sacs called cisternae.


152. What is the function of the Golgi apparatus?
     The Golgi apparatus is involved in the modification, packaging, and distribution of proteins and lipids for secretion or for use within the cell.


153. What is the function of lysosomes in the cell?
     Lysosomes are responsible for the digestion of unwanted materials within the cell, such as old organelles or foreign particles.


154. What are lysosomes filled with?
     Lysosomes are filled with digestive enzymes that break down large molecules into smaller components.


155. What happens when the cell needs to get rid of waste material?
     When the cell needs to get rid of waste material, the lysosomes fuse with the waste material and break it down into simpler forms that can be eliminated from the cell.


156. What is the powerhouse of the cell?
     The mitochondria are often referred to as the powerhouse of the cell.


157. What is the function of mitochondria?
     Mitochondria are responsible for producing energy in the form of ATP (adenosine triphosphate) through cellular respiration.


158. What is the unique feature of mitochondria?
     Mitochondria have their own DNA, separate from the cell's nuclear DNA.


159. What is the role of plastids in plant cells?
     Plastids are involved in processes like photosynthesis, storage of starch, pigments, and other compounds in plant cells.


160. What are the three types of plastids?
     The three types of plastids are chloroplasts, chromoplasts, and leucoplasts.
     
     



161. What is the function of chloroplasts?
     Chloroplasts are responsible for photosynthesis, the process by which plants convert sunlight into chemical energy.


162. What is the function of chromoplasts?
     Chromoplasts are responsible for the synthesis and storage of pigments, giving fruits and flowers their vibrant colors.


163. What is the function of leucoplasts?
     Leucoplasts are involved in the synthesis and storage of starch, oils, and proteins.


164. What is the main difference between prokaryotic and eukaryotic cells?
     The main difference between prokaryotic and eukaryotic cells is the presence of a distinct nucleus and membrane-bound organelles in eukaryotic cells, while prokaryotic cells lack these structures.


165. What is the significance of studying cell structure and organelles?
     Studying cell structure and organelles helps us understand the fundamental units of life and the processes that occur within cells, contributing to advancements in various fields, including medicine, biotechnology, and genetics.


166. Why do we put iodine solution on the temporary mount of onion peel? What is the purpose of using iodine solution in observing the peel?
     The iodine solution is applied to the temporary mount of the onion peel to stain the cells and make certain structures more visible under a microscope. It helps in highlighting specific cellular components and provides contrast for better observation. By staining the cells, the iodine solution makes it easier to identify and study different structures, such as the nucleus and cell walls. This staining technique enhances the visibility and clarity of the cellular components, allowing for a more detailed examination of the onion peel cells.
     


167. What would happen if we tried observing the onion peel without putting iodine solution? How would the observation differ from when iodine solution is used? 
     If the onion peel is observed without applying iodine solution, the cellular structures would be less visible, making it difficult to observe and identify specific components. The observation would lack contrast, and the cells might appear transparent or unclear under the microscope. The absence of staining would make it challenging to distinguish various cell organelles and structures. On the other hand, when iodine solution is used, it selectively interacts with certain cellular components, staining them and making them stand out against the background. This allows for a more detailed examination and identification of specific cell structures.


168. When iodine solution is applied to the onion peel, does each cell get evenly colored? Explain the differential coloring of different regions within the cells.

     No, each cell does not get evenly colored when iodine solution is applied to the onion peel. Different regions within the cells get colored differentially based on their chemical composition. Some regions appear darker or more intensely stained, while others may appear lighter. This differential coloring occurs because different cellular components react differently with the iodine solution. For example, the nucleus, which contains DNA, tends to stain more deeply due to its high DNA content. The cell walls and other organelles may show varying degrees of staining, resulting in a non-uniform color distribution within the cells.



169. Besides iodine solution, what other staining solutions can be used to stain cells? Provide examples and their potential applications.

     In addition to iodine solution, other staining solutions can be used to stain cells for observation under a microscope. Two examples of such staining solutions are safranin solution and methylene blue solution. Safranin solution stains cells in a red or pink color, and it can be used to visualize different types of tissues or cell structures. Methylene blue solution, on the other hand, stains cells in a blue color and is commonly used for highlighting cell nuclei. These staining solutions provide different color variations and can aid in the identification and observation of specific cellular structures or components, depending on the research or educational objectives.



170. Describe the process of preparing cells from the inside surface of the cheek for observation under a microscope. Outline the steps involved and the materials used.

     To prepare cells from the inside surface of the cheek for observation under a microscope, the following steps are involved:

     • Take a glass slide and place a drop of water on it.
     • Gently scrape the inside surface of the cheek using an ice-cream spoon to collect the material.
     • Using a needle, transfer the collected material onto the glass slide and spread it evenly.
     • Add a drop of methylene blue solution to the material on the slide to color the cells.
     • Place a cover-slip on top of the material to create a thin, flat layer for observation.
     • Ensure that the cover-slip is positioned carefully to avoid trapping air bubbles.

     By following these steps and using the appropriate materials, such as a glass slide, water, ice-cream spoon, needle, methylene blue solution, and a cover-slip, cells from the inside surface of the cheek can be prepared for microscopic observation.



171. What can be observed when examining the cells from the inside surface of the cheek under a microscope?
     Describe the shape of the cells and illustrate it on the observation sheet.When examining the cells from the inside surface of the cheek under a microscope, one can observe the presence of epithelial cells. These cells are typically squamous or flat in shape, resembling thin scales or pancakes. They are closely packed and form a protective layer on the inner surface of the cheek. Under the microscope, the cells may appear irregularly shaped due to their arrangement and overlapping nature. Illustrating the observed cells on the observation sheet would involve drawing a representation of the squamous cells with their flat and irregular shapes, showcasing their arrangement and characteristics as observed through the microscope.
     
     
172. Can you name the two organelles we have studied that contain their own genetic material?
     The two organelles that contain their own genetic material are mitochondria and plastids.


173. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
     If the organization of a cell is destroyed due to some physical or chemical influence, the cell may lose its ability to function properly or even die.


174. Why are lysosomes known as suicide bags?
     Lysosomes are known as "suicide bags" because if they are damaged or disrupted, they can burst and release their powerful digestive enzymes, which can lead to the digestion of the cell itself.


175. Where are proteins synthesized inside the cell?
     Proteins are synthesized inside the cell in the rough endoplasmic reticulum (RER) and also in the ribosomes associated with the RER.


176. What is the function of the Golgi apparatus in a cell?
     The Golgi apparatus functions in the storage, modification, and packaging of substances manufactured in the celIt receives materials from the endoplasmic reticulum (ER) and dispatches them to various targets inside and outside the cell.


177. What are the two types of plastids found in plant cells?
     The two types of plastids found in plant cells are chromoplasts (colored plastids) and leucoplasts (white or colorless plastids).


178. What is the primary function of chloroplasts in plant cells?
     The primary function of chloroplasts in plant cells is photosynthesis, which involves capturing sunlight and converting it into chemical energy in the form of glucose.


179. What is the role of vacuoles in plant cells?
     Vacuoles in plant cells act as storage sacs for solid or liquid contentThey contain cell sap and help maintain turgidity and rigidity in the celVacuoles also store important substances such as amino acids, sugars, organic acids, and proteins.


180. What are the two main types of cell division?
     The two main types of cell division are mitosis and meiosis.




181. How many daughter cells are produced in mitosis?
     Do they have the same number of chromosomes as the mother cell?
     In mitosis, two identical daughter cells are produced, and they have the same number of chromosomes as the mother cell.


182. What is the difference between mitosis and meiosis in terms of the number of chromosomes in daughter cells?
     In meiosis, four daughter cells are produced, and each daughter cell has half the number of chromosomes compared to the mother celThis reduction in chromosome number is important for sexual reproduction.


183. Why do cells in organisms divide?
     Cells in organisms divide for various reasons, including growth of the body, replacement of dead or injured cells, and the formation of gametes for reproduction.


184. How are cells enclosed in organisms?
     Cells are enclosed by a plasma membrane composed of lipids and proteins.


185. What is the function of the cell membrane?
     The cell membrane is an active part of the celIt regulates the movement of materials between the ordered interior of the cell and the outer environment.


186. In plant cells, what is located outside the cell membrane?
     In plant cells, a cell wall composed mainly of cellulose is located outside the cell membrane.


187. How do plant cells withstand hypotonic media without bursting?
     The presence of the cell wall enables the cells of plants, fungi, and bacteria to exist in hypotonic media without bursting.


188. What separates the nucleus from the cytoplasm in eukaryotes?
     The nucleus in eukaryotes is separated from the cytoplasm by a double-layered membrane.


189. What is the function of the endoplasmic reticulum (ER) in a cell?
     The ER functions both as a passageway for intracellular transport and as a manufacturing surface.


190. Who first described the Golgi apparatus?
     The Golgi apparatus was first described by Camillo Golgi.


191. What is the function of the Golgi apparatus in protein synthesis?
     The Golgi apparatus is involved in the storage, modification, and packaging of products in vesicles, including proteins synthesized near the endoplasmic reticulum.


192. Why are lysosomes also known as the 'suicide bags' of a cell?
     Lysosomes are known as the 'suicide bags' of a cell because, during disturbances in cellular metabolism or damage, they may burst and the enzymes inside can digest their own cell.


193. What is the function of mitochondria in a cell?
     Mitochondria are known as the powerhouses of the cell and release energy in the form of ATP (Adenosine triphosphate) through various chemical reactions.


194. What is ATP and its role in the cell?
     ATP is Adenosine triphosphate, known as the energy currency of the celIt provides the energy required for various chemical activities needed for life, including the synthesis of new compounds and mechanical work.


195. What is the internal structure of chloroplasts?
     The internal organization of chloroplasts consists of numerous membrane layers embedded in a material called the stroma.


196. Do plastids have their own DNA and ribosomes?
     Yes, like mitochondria, plastids also have their own DNA and ribosomes, allowing them to synthesize some of their own proteins.


197. How do vacuoles differ in size between animal cells and plant cells?
     Vacuoles are small-sized in animal cells, while plant cells have very large vacuoles, with the central vacuole often occupying 0-0% of the cell volume.


198. What substances are stored in vacuoles?
     Vacuoles store various substances of importance in the life of the cell, including amino acids, sugars, various organic acids, and some proteins.


199. What is the purpose of cell division in organisms?
     Cell division in organisms serves the purpose of growth, replacing old or injured cells, and forming gametes required for reproduction.




200. What are the functions of the fundamental structural unit of life, the cell?
     The functions of cells include respiration, obtaining nutrition, clearing waste material, and forming new proteins.


201. What are the two main types of cell division involved in the formation of new cells?
     The two main types of cell division involved in the formation of new cells are mitosis and meiosis.


202. How many daughter cells are formed in mitosis, and do they have the same number of chromosomes as the mother cell?
     In mitosis, two daughter cells are formed, and they have the same number of chromosomes as the mother cell.


203. What happens to the chromosome number in daughter cells formed by meiosis?
     In meiosis, the chromosome number is reduced to half in daughter cells compared to the mother cell.


204. What is the composition of the cell wall in plant cells?
     The cell wall in plant cells is mainly composed of cellulose.


205. What is the role of chloroplasts in photosynthesis?
     Chloroplasts play a crucial role in photosynthesis by capturing sunlight and converting it into chemical energy in the form of glucose.


206. What are the primary functions of leucoplasts in plant cells?
     The primary functions of leucoplasts in plant cells are storage of materials such as starch, oils, and protein granules.


207. How do prokaryotic cells differ from eukaryotic cells?
     Prokaryotic cells have no membrane-bound organelles, their chromosomes are composed of only nucleic acid, and they have small ribosomes as organelles.


208. What is the role of vacuoles in single-celled organisms like Amoeba?
     In single-celled organisms like Amoeba, the food vacuole contains the food items that the Amoeba has consumed.


209. In addition to energy storage, what other important functions do mitochondria perform?
     Besides energy storage, mitochondria have their own DNA and ribosomes, allowing them to synthesize some of their own proteins.


210. What is the role of the Golgi apparatus in the formation of lysosomes?
     The Golgi apparatus is involved in the formation of lysosomes, as lysosomes originate from the Golgi apparatus.


211. How do lysosomes contribute to cell cleanliness?
     Lysosomes help keep the cell clean by digesting foreign materials, such as bacteria or food particles, as well as worn-out cell organelles.


212. What happens if lysosomes are damaged or disrupted?
     If lysosomes are damaged or disrupted, they may burst, releasing their digestive enzymes and potentially leading to the digestion of the cell itself.


213. What is the significance of lysosomes in cellular metabolism?
     Lysosomes play a crucial role in cellular metabolism by breaking down complex substances into simpler substances through their powerful digestive enzymes.


214. How do mitochondria release energy in the form of ATP?
     Mitochondria release energy in the form of ATP through ATP-generating chemical reactions that take place in the inner membrane, which is deeply folded to increase surface area.


215. What is the role of lysosomes in the liver cells of vertebrates?
     In the liver cells of vertebrates, lysosomes are involved in detoxifying many poisons and drugs, serving as a crucial part of the cell's waste disposal system.


216. How do plastids differ in function between chromoplasts and leucoplasts?
     Chromoplasts, specifically chloroplasts, are involved in photosynthesis, while leucoplasts primarily function as storage organelles.


217. What is the function of the central vacuole in plant cells?
     The central vacuole in plant cells helps maintain the turgidity and rigidity of the cell, as well as store important substances, including wastes.


218. What is the significance of the fundamental unit of life, the cell, in living organisms?
     The cell's fundamental structural organization and functional capabilities allow it to perform essential life processes such as respiration, obtaining nutrition, waste clearance, and protein synthesis.


219. How do cells maintain their structure and ability to function?
     Cells maintain their structure and ability to function through the organization of their membranes and organelles in specific ways, which enable them to carry out essential cellular processes.


220. What is the composition of the plasma membrane?
     The plasma membrane is composed of lipids and proteins.




221. What is the role of the cell membrane in a cell?
     The cell membrane regulates the movement of materials between the cell's interior and the external environment.


222. What is the function of the cell wall in plant cells?
     The cell wall provides structural support and protection for plant cells.


223. Why can plant cells exist in hypotonic media without bursting?
     The presence of the cell wall in plant cells allows them to withstand hypotonic conditions without bursting.


224. How does the nucleus of eukaryotic cells contribute to cell function?
     The nucleus, separated from the cytoplasm by a double-layered membrane, directs the life processes of the cell.


225. What are the roles of the endoplasmic reticulum (ER) in a cell?
     The endoplasmic reticulum functions as a passageway for intracellular transport and as a site for the synthesis of various substances.


226. How does the Golgi apparatus package and distribute cellular products?
     The Golgi apparatus packages and modifies substances synthesized near the endoplasmic reticulum, preparing them for distribution to various targets inside and outside the cell.


227. What is the main function of chromoplasts in plant cells?
     Chromoplasts, particularly chloroplasts, are responsible for photosynthesis in plant cells.


228. How do vacuoles contribute to the turgidity and rigidity of plant cells?
     The large central vacuole in plant cells stores cell sap, providing turgidity and rigidity to maintain the cell's shape.


229. How do vacuoles function in waste storage in plant cells?
     Vacuoles in plant cells can store various substances, including wastes and other important materials for cellular processes.


230. How do prokaryotic cells differ from eukaryotic cells in terms of their structure and organelles?
     Prokaryotic cells lack membrane-bound organelles, have nucleic acid-based chromosomes, and possess smaller ribosomes compared to eukaryotic cells.


231. What is the role of cell division in growth and tissue repair?
     Cell division allows for the growth of organisms and the replacement of old or injured cells.


232. How does meiosis differ from mitosis in terms of the number of daughter cells and chromosome number?
     In meiosis, four daughter cells are formed, each with half the number of chromosomes compared to the mother cell, while in mitosis, two daughter cells are formed with the same number of chromosomes as the mother cell.


233. What is the significance of cells dividing to form gametes?
     Cells dividing to form gametes is crucial for sexual reproduction, as gametes combine during fertilization to produce offspring with unique genetic characteristics.


234. What are the functions of the cell wall, cell membrane, and nucleus collectively in a cell?
     The cell wall provides support and protection, the cell membrane regulates material exchange, and the nucleus directs cell activities, collectively contributing to cell structure and function.


235. What is the role of lysosomes in cellular digestion?
     Lysosomes aid in cellular digestion by containing powerful digestive enzymes that break down foreign materials and worn-out cell organelles.


236. Why are lysosomes referred to as "suicide bags" of a cell?
     Lysosomes are called "suicide bags" because if they are damaged or disrupted, they may burst, releasing their enzymes and causing the digestion of their own cell.


237. How do lysosomes contribute to maintaining cell cleanliness?
     Lysosomes help keep the cell clean by digesting foreign materials, such as bacteria or food particles, as well as removing old organelles.


238. What is the role of mitochondria in energy production?
     Mitochondria, known as the powerhouses of the cell, release energy in the form of ATP through chemical reactions, providing the energy needed for various cellular activities.


239. What is the function of ATP in the cell?
     ATP, also known as adenosine triphosphate, serves as the energy currency of the cell, providing energy for cellular processes such as synthesis and mechanical work.


240. What is the significance of plastids in plant cells?
     Plastids, specifically chloroplasts, are crucial for photosynthesis in plants, allowing them to convert sunlight into chemical energy.




241. What are the structural similarities between plastids and mitochondria?
     Plastids and mitochondria share similarities in their external structure, possessing numerous membrane layers and having their own DNA and ribosomes.


242. What is the purpose of the Golgi apparatus in cellular function?
     The Golgi apparatus plays a role in the storage, modification, and packaging of cellular products, preparing them for transport within and outside the cell.


243. How do vacuoles differ in size between animal and plant cells?
     Vacuoles in animal cells are small-sized, while plant cells have significantly larger vacuoles, with the central vacuole often occupying a substantial portion of the cell volume.


244. What substances are stored in vacuoles in plant cells?
     Vacuoles in plant cells store various substances such as amino acids, sugars, organic acids, proteins, and important cellular materials.


245. How do vacuoles contribute to water balance in some unicellular organisms?
     Specialized vacuoles in some unicellular organisms help expel excess water and waste products from the cell, maintaining water balance.


246. What is the role of the cell wall in protecting plant cells?
     The cell wall provides structural support and protection, acting as a barrier against external mechanical forces and pathogens.


247. How does the process of cell division contribute to tissue growth and repair?
     Cell division allows for the increase in cell number, enabling tissue growth and facilitating the replacement of damaged or dead cells.


248. What is the primary function of the Golgi apparatus in the synthesis of complex sugars?
     The Golgi apparatus is involved in the synthesis of complex sugars from simple sugars, contributing to the cell's production of various carbohydrates.


249. How does the structure of mitochondria enhance ATP production?
     The inner membrane of mitochondria is deeply folded, increasing the surface area available for ATP-generating chemical reactions, thereby enhancing ATP production.


250. What is the function of the Golgi apparatus in the formation of lysosomes?
     The Golgi apparatus is involved in the formation of lysosomes, where it plays a role in packaging and modifying substances that will eventually become lysosomes.


251. How are lysosomes involved in cellular metabolism?
     During cellular metabolism, lysosomes participate in the breakdown of complex substances into simpler substances, thanks to their powerful digestive enzymes.


252. What is the purpose of the internal organization of chloroplasts?
     The internal organization of chloroplasts, consisting of numerous membrane layers embedded in a material called the stroma, allows for efficient photosynthesis and the synthesis of various pigments.


253. How do plastids differ from mitochondria in terms of their genetic material?
     Plastids, like mitochondria, have their own DNA and ribosomes, enabling them to synthesize some of their own proteins.


254. What is the role of the Golgi apparatus in the storage of cellular products?
     The Golgi apparatus functions in the storage of cellular products by packaging and organizing them into vesicles for future use or transport.


255. What are the functions of chromoplasts and leucoplasts in plant cells?
     Chromoplasts contain pigments, including chlorophyll, and participate in photosynthesis, while leucoplasts primarily serve as storage organelles for substances like starch, oils, and proteins.


256. How do vacuoles contribute to the overall function of plant cells?
     Vacuoles play a significant role in plant cells by storing important substances, maintaining cell turgidity and rigidity, and participating in the excretion of excess water and waste products.


257. How do lysosomes contribute to maintaining cellular homeostasis?
     Lysosomes aid in maintaining cellular homeostasis by digesting foreign materials and removing worn-out organelles, ensuring the overall cleanliness and proper functioning of the cell.


258. What are the differences between mitosis and meiosis in terms of chromosome number?
     Mitosis results in daughter cells with the same number of chromosomes as the mother cell, while meiosis produces daughter cells with half the number of chromosomes.


259. Why do cells divide in organisms?
     Cells divide in organisms to facilitate growth, replace old and damaged cells, and produce gametes necessary for reproduction.


260. What is the significance of new cell formation in organisms?
     New cell formation is essential for the growth and development of organisms, as well as for tissue repair and the production of gametes required for reproduction.




261. What is the function of the cell membrane in regulating the movement of materials?
     The cell membrane, composed of lipids and proteins, actively regulates the movement of materials between the cell's interior and the external environment.


262. How does the presence of a cell wall benefit plant, fungi, and bacterial cells?
     The presence of a cell wall, mainly composed of cellulose in plant cells, provides structural support and prevents bursting in hypotonic media.


263. What is the role of the nucleus in eukaryotic cells?
     The nucleus, separated from the cytoplasm by a double-layered membrane, directs the life processes of the cell and contains the cell's genetic material.


264. What are the functions of the endoplasmic reticulum (ER) in the cell?
     The endoplasmic reticulum serves as a passageway for intracellular transport and as a manufacturing surface for the synthesis of proteins and lipids.


265. What are the main types of cell division?
     The main types of cell division are mitosis and meiosis.


266. How does mitosis contribute to tissue growth and repair in organisms?
     Mitosis allows for the growth of tissues and facilitates the replacement of old, dead, or injured cells.


267. How does meiosis differ from mitosis in terms of the number of daughter cells produced?
     Meiosis produces four new cells, while mitosis produces two daughter cells.


268. What is the purpose of the internal membrane structure of mitochondria?
     The folded inner membrane of mitochondria increases the surface area available for ATP production through chemical reactions.


269. Why are mitochondria referred to as the powerhouses of the cell?
     Mitochondria produce energy in the form of ATP, which is utilized for various chemical activities required for life, earning them the nickname "powerhouses of the cell.


270. What is the function of the Golgi apparatus in the cell?
     The Golgi apparatus functions in the storage, modification, and packaging of substances manufactured within the cell.


271. What is the primary function of leucoplasts in plant cells?
     Leucoplasts primarily serve as organelles for the storage of materials such as starch, oils, and protein granules.


272. How do vacuoles contribute to the maintenance of plant cell turgidity?
     Vacuoles, particularly the central vacuole in plant cells, are filled with cell sap and provide turgidity and rigidity to the cell.


273. What are the two types of plastids found in plant cells?
     The two types of plastids found in plant cells are chromoplasts and leucoplasts.


274. What are some substances stored in vacuoles of plant cells?
     Vacuoles in plant cells store various substances, including amino acids, sugars, organic acids, and certain proteins.


275. What happens when lysosomes are damaged or disrupted?
     When lysosomes are damaged, they may burst, leading to the digestion of their own cell components by the released enzymes.


276. What is the significance of mitochondria having their own DNA and ribosomes?
     The presence of DNA and ribosomes in mitochondria allows them to synthesize some of their own proteins, contributing to their functions within the cell.


277. How does the cell wall in plant cells differ from the cell membrane?
     The cell wall, composed mainly of cellulose, is located outside the cell membrane and provides structural support and protection to the plant cell.


278. What is the role of lysosomes in the cell?
     Lysosomes serve as a waste disposal system in the cell, digesting foreign materials and worn-out cell organelles.


279. How do lysosomes break down complex substances?
     Lysosomes contain powerful digestive enzymes capable of breaking down all organic material into simpler substances.


280. What is the function of the Golgi apparatus in relation to lysosomes?
     The Golgi apparatus is involved in the formation of lysosomes, contributing to their structure and function.




281. What is the significance of lysosomes being called "suicide bags" of a cell?
     Lysosomes may burst and digest their own cell if there is a disturbance in cellular metabolism, hence the term "suicide bags.


282. "What is the energy currency of the cell?
     The energy currency of the cell is ATP (Adenosine triphosphate).


283. How is ATP generated in the cell?
     Mitochondria, known as the powerhouses of the cell, release energy in the form of ATP through chemical reactions.


284. What is the function of chloroplasts in plant cells?
     Chloroplasts, a type of plastid, are responsible for photosynthesis in plants.


285. What is the purpose of the internal membrane layers in chloroplasts?
     The internal membrane layers in chloroplasts provide a large surface area for various cellular processes, including photosynthesis.


286. How do vacuoles contribute to maintaining cell turgidity in plant cells?
     Vacuoles in plant cells are filled with cell sap, providing turgidity and rigidity to maintain the structure of the cell.


287. What are the two organelles that contain their own genetic material?
     The two organelles that contain their own genetic material are mitochondria and chloroplasts.


288. What happens when the organization of a cell is disrupted due to physical or chemical influences?
     When the organization of a cell is disrupted, it can lead to dysfunction and impaired cellular processes.


289. How does the Golgi apparatus participate in the storage, modification, and packaging of substances?
     The Golgi apparatus receives materials synthesized near the endoplasmic reticulum (ER) and processes them for storage or transport to various targets within and outside the cell.


290. What are the main functions of chromoplasts and leucoplasts?
     Chromoplasts, particularly chloroplasts, are involved in photosynthesis, while leucoplasts primarily function in the storage of materials such as starch, oils, and proteins.


291. How do plant cells, fungi, and bacterial cells benefit from having a cell wall?
     The presence of a cell wall in plant cells, fungi, and bacterial cells provides structural support and protection, allowing them to withstand hypotonic environments without bursting.


292. How does mitosis differ from meiosis in terms of the number of daughter cells produced?
     Mitosis produces two daughter cells that are genetically identical to the parent cell, while meiosis produces four daughter cells with half the number of chromosomes as the parent cell.


293. What is the fundamental unit of life in living organisms?
     The fundamental unit of life in living organisms is the cell.


294. Why do cells undergo division in organisms?
     Cells undergo division in organisms for growth, repair, and the production of gametes required for reproduction.


295. How does the presence of a double-layered membrane in the nucleus separate it from the cytoplasm?
     The double-layered membrane in the nucleus acts as a barrier, separating the nucleus from the cytoplasm and regulating the movement of substances.


296. What are the main functions of the Golgi apparatus?
     The Golgi apparatus is responsible for the storage, modification, and packaging of substances within the cell.


297. What is the primary function of plastids in plant cells?
     Plastids, such as chromoplasts and leucoplasts, play essential roles in processes like photosynthesis and storage in plant cells.


298. What is the role of the ER in the cell?
     The endoplasmic reticulum functions as a passageway for intracellular transport and as a site for the synthesis of proteins and lipids.


299. What is the function of lysosomes in the cell?
     Lysosomes act as a waste disposal system, breaking down foreign materials and worn-out cell organelles.


300. What is the primary function of mitochondria in the cell?
     Mitochondria are known as the powerhouses of the cell, producing ATP, the energy currency used for various cellular activities.




301. What is the purpose of vacuoles in plant cells?
     Vacuoles in plant cells serve as storage sacs for various substances, providing turgidity and helping maintain cell structure.


302. What are the characteristics of prokaryotic cells?
     Prokaryotic cells lack membrane-bound organelles, have nucleic acid-based chromosomes, and possess small ribosomes.


303. What is the purpose of the Golgi apparatus in the cell?
     The Golgi apparatus functions in the storage, modification, and packaging of substances synthesized by the cell.


304. How do plastids contribute to the functioning of plant cells?
     Plastids, such as chloroplasts and leucoplasts, perform vital functions in photosynthesis, storage, and the synthesis of various compounds.


305. How do cells acquire their structure and ability to function?
     Cells acquire their structure and ability to function through the organization of their membranes and organelles in specific ways.


306. How does mitosis contribute to growth and tissue repair in organisms?
     Mitosis is responsible for the division of cells, leading to growth and the replacement of old, dead, or injured cells.


307. What is the significance of meiosis in the formation of gametes?
     Meiosis is the process through which specific cells divide to produce gametes, which are required for reproduction.


308. How does the chromosome number change during meiosis?
     During meiosis, the chromosome number is reduced to half in the daughter cells compared to the mother cell.


309. What is the fundamental structural unit of living organisms?
     The fundamental structural unit of living organisms is the cell.


310. Why is cell division important in living organisms?
     Cell division is essential for growth, the replacement of damaged cells, and the production of gametes necessary for reproduction.
     
     
311. Name two structures found in plant cells but not in animal cells.
     Cell wall and chloroplast.
     
     
312. What is a hypotonic solution?
     A solution having solute concentration lower than that of the cell sap is called a hypotonic solution.
     
     
313. What is the outermost layer found in animal cells?
     Plasma membrane.
     
     
314. Which organelle is the storage sac of solid and liquid materials?
     Vacuoles.
     
     
315. Define diffusion.
     Movement of molecules from a region of higher concentration to a region of lower concentration is called diffusion.
     
     
316. What is the outermost layer found in the plant cell?
     Cell wall.
     
     
317. Which organelle serves as a channel for transport of materials between cytoplasm and nucleus?
     Endoplasmic reticulum.
     
     
318. Which organelle is involved in the formation of lysosomes?
     Golgi apparatus.
     
     
319. What is endocytosis?
     Endocytosis is the ingestion or engulfment of food and other material by folding of the plasma membrane, as seen in Amoeba.
     
     
320. What is the intracellular source of digestive enzyme?
     Lysosome.
     
     
     
     
321. Which organelle is associated with ribosome formation?
     Nucleolus.
     
     
322. What is a nucleoid?
     The undefined nuclear region in the cytoplasm of prokaryotes is known as nucleoid.
     
     
323. Name two structures found in animal cells but not in plant cells.
     Lysosomes and centrioles.
     
     
324. What is the intracellular source of digestive enzyme?
     Lysosome.
     
     
325. What is isotonic solution?
     A solution having solute concentration same as that of the cell sap is called isotonic solution.
     
     
326. What is the outermost layer found in animal cells?
     Plasma membrane.
     
     
327. Which organelle detoxifies many poisons and drugs in a cell?
     Peroxisome.
     
     
328. Which organelles, other than the nucleus, contain DNA?
     Mitochondria and plasmids contain DNA.
     
     
329. Name a cell organelle which is non-membranous.
     Ribosome.
     
     
330. Which organelle is the storage sac of solid and liquid materials?
     Vacuoles.
     
     
331. What is active transport?
     The movement of molecules across a membrane in cells against a concentration gradient with the help of ATP units is called active transport.
     
     
332. What is the hypotonic solution?
     A solution having solute concentration lower than that of the cell sap is called a hypotonic solution.
     
     
333. What is a microscope?
     Microscope is an optical instrument consisting of a lens or combination of lenses which renders minute objects distinctly visible.
     
     
334. Name the only cell organelle seen in prokaryotic cell.
     Ribosomes.
     
     
335. What is the outermost layer found in the plant cell?
     Cell wall.
     
     
336. What is the intracellular source of digestive enzyme?
     Lysosome.
     
     
337. Which organelle is involved in the formation of lysosomes?
     Golgi apparatus.
     
     
338. What are chromosomes made up of?
     Chromosomes are made up of DNA and protein.
     
     
339. What is endocytosis?
     Endocytosis is the process by which cells engulf or ingest food and other materials by folding the plasma membrane, as observed in Amoeba.
     
     
340. Which organelle serves as a channel for the transport of materials between the cytoplasm and nucleus?
     Endoplasmic reticulum.
     
     
341. What is a nucleoid?
     The nucleoid is the undefined nuclear region in the cytoplasm of prokaryotes.
     
     
342. Name a non-membranous cell organelle.
     Ribosome.

Class 9 Science Chapter 5 - The Fundamental Unit of Life Important Questions and Answers

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Class 9 CBSE Important Questions and Answers
Chapter 5 - The Fundamental Unit of Life

Class 9 ncert cbse important questions ajs