20 Very Short Question Answers
Question 1. What is the basic unit of life?
Answer: The cell is the basic unit of life.
Question 2. Who discovered cells?
Answer: Robert Hooke discovered cells.
Question 3. What is the outer boundary of a cell called?
Answer: It is called the cell membrane or plasma membrane.
Question 4. What is osmosis?
Answer: Osmosis is the movement of water through a selectively permeable membrane.
Question 5. Which cells have a cell wall?
Answer: Plant, fungal, and bacterial cells have a cell wall.
Question 6. What is the plant cell wall mainly made of?
Answer: It is mainly made of cellulose.
Question 7. Which cell organelle controls cell activities?
Answer: The nucleus controls cell activities.
Question 8. What is the genetic material present in chromosomes?
Answer: DNA is the genetic material present in chromosomes.
Question 9. What are genes?
Answer: Genes are functional segments of DNA.
Question 10. Which organelle is called the protein factory?
Answer: Ribosomes are called the protein factories.
Question 11. What does RER stand for?
Answer: RER stands for Rough Endoplasmic Reticulum.
Question 12. Which organelle packages and transports materials?
Answer: The Golgi apparatus packages and transports materials.
Question 13. Which organelle is called the powerhouse of the cell?
Answer: Mitochondria are called the powerhouse of the cell.
Question 14. What is ATP?
Answer: ATP is the energy currency of the cell.
Question 15. Which plastid performs photosynthesis?
Answer: Chloroplast performs photosynthesis.
Question 16. Which plastid stores food?
Answer: Leucoplast stores food.
Question 17. What is the large storage sac in plant cells called?
Answer: It is called a vacuole.
Question 18. Which type of cell division produces two identical daughter cells?
Answer: Mitosis produces two identical daughter cells.
Question 19. Which type of cell division forms gametes?
Answer: Meiosis forms gametes.
Question 20. What is contact inhibition?
Answer: It is the process in which many animal cells stop dividing when they come in contact with neighbouring cells.
15 Short Question Answers
Question 1. Why are microscopes needed to study cells?
Answer: Cells are usually too small to be seen with the naked eye because the human eye has limited resolution. Microscopes magnify cells and help us see their structure clearly. Light microscopes are used in school laboratories, while electron microscopes reveal finer details.
Question 2. What is the function of the cell membrane?
Answer: The cell membrane surrounds the cell and protects its contents. It is selectively permeable and controls the movement of substances in and out of the cell. It also helps the cell interact with its environment.
Question 3. What is the difference between diffusion and osmosis?
Answer: Diffusion is the movement of particles from a region of higher concentration to lower concentration. Osmosis is the movement of water through a selectively permeable membrane from a region of higher water concentration to lower water concentration.
Question 4. Why do plant cells have a cell wall?
Answer: Plant cells have a cell wall to provide shape, protection, and rigidity. Since plants are fixed in one place, they need support to withstand wind, rain, and other environmental stresses. The cell wall also helps the plant remain upright.
Question 5. Differentiate between prokaryotic and eukaryotic cells.
Answer: Prokaryotic cells do not have a well-defined nucleus or membrane-bound organelles. Their genetic material lies in a nucleoid. Eukaryotic cells have a membrane-bound nucleus and several membrane-bound organelles. Plant and animal cells are eukaryotic, while bacteria are prokaryotic.
Question 6. What is the role of the nucleus in a cell?
Answer: The nucleus controls all the activities of the cell. It contains DNA, genes, and chromosomes, which carry hereditary information. It also helps in the transfer of information from one generation to the next.
Question 7. What are ribosomes?
Answer: Ribosomes are tiny structures found freely in the cytoplasm or attached to the rough endoplasmic reticulum. They are the sites of protein synthesis and are therefore called protein factories.
Question 8. Write the functions of RER and SER.
Answer: RER has ribosomes on its surface and helps in protein synthesis and secretion. SER does not have ribosomes and helps in the synthesis and storage of lipids and some hormones.
Question 9. Why is Golgi apparatus called the packaging centre of the cell?
Answer: The Golgi apparatus modifies, sorts, and packages proteins and lipids into vesicles. These vesicles carry the materials to different parts of the cell or outside it. That is why it is called the packaging and shipping centre of the cell.
Question 10. What are lysosomes? State one function.
Answer: Lysosomes are membrane-bound sacs filled with digestive enzymes. Their main function is to break down wastes, foreign materials, and worn-out cell organelles, keeping the cell clean and healthy.
Question 11. Why are mitochondria called the powerhouse of the cell?
Answer: Mitochondria are called the powerhouse of the cell because they release energy from food during cellular respiration. This energy is stored as ATP and used for various cellular activities.
Question 12. Name the types of plastids and write one function of each.
Answer: The main types of plastids are chloroplasts, chromoplasts, and leucoplasts. Chloroplasts perform photosynthesis, chromoplasts give colour to flowers and fruits, and leucoplasts store food such as starch, oils, or proteins.
Question 13. What is the importance of vacuoles in plant cells?
Answer: Vacuoles store water, minerals, sugars, and waste materials. In plant cells, the large central vacuole helps maintain internal pressure, keeps the cell firm, and prevents the plant from wilting.
Question 14. What is mitosis? Why is it important?
Answer: Mitosis is a type of cell division in which one parent cell forms two genetically identical daughter cells. It is important for growth, repair of damaged tissues, maintenance of body cells, and asexual reproduction.
Question 15. State the Cell Theory.
Answer: Cell Theory states that all living organisms are made up of one or more cells, the cell is the basic unit of structure and function in living beings, and all cells arise from pre-existing cells.
10 Long Question Answers
Question 1. Explain the structure and functions of the cell membrane.
Answer: The cell membrane, also called the plasma membrane, is a thin outer boundary that surrounds the cell and protects its contents. It gives the cell its individuality and helps separate the cell from its surroundings. The cell membrane is selectively permeable, which means it allows only certain substances to move in and out of the cell. This helps the cell maintain proper internal conditions.
Structurally, the cell membrane is made up of lipids and proteins. According to the fluid-mosaic model, it consists of a lipid bilayer with proteins embedded in it. The lipid molecules can move sideways, and proteins act like gatekeepers, helping substances pass through. The cell membrane is important for exchange of gases, water, food, and wastes. It also helps cells communicate with neighbouring cells and respond to the environment.
Question 2. Describe the role of the cell wall in plant cells. How is it different from the cell membrane?
Answer: The cell wall is a rigid outer covering present outside the cell membrane in plant cells. It provides shape, protection, and structural support to the plant cell. Since plants are fixed in one place, they need a strong structure to withstand environmental stresses like wind and rain. The cell wall helps leaves and flowers remain firm and helps plants stay upright.
The plant cell wall is mainly made of cellulose. It is permeable, which means water and some dissolved substances can pass through it. In contrast, the cell membrane is selectively permeable and controls what enters and leaves the cell. Another major difference is that the cell wall is non-living and rigid, while the cell membrane is living and flexible. Animal cells do not have a cell wall, which allows them to change shape easily.
Question 3. Differentiate between prokaryotic and eukaryotic cells in detail.
Answer: Prokaryotic and eukaryotic cells differ in structure and complexity. Prokaryotic cells are simpler and smaller. They do not have a well-defined nucleus, and their genetic material is present in a region called the nucleoid. They also lack membrane-bound organelles. Bacteria are examples of prokaryotic cells.
Eukaryotic cells are larger and more complex. They have a well-defined nucleus enclosed by a nuclear membrane. They also contain membrane-bound organelles such as mitochondria, Golgi apparatus, lysosomes, and endoplasmic reticulum. Plant and animal cells are examples of eukaryotic cells.
Prokaryotic cells are usually unicellular, while eukaryotic organisms may be unicellular or multicellular. In prokaryotes, most cell activities occur directly in the cytoplasm. In eukaryotes, different organelles carry out specialised functions. Thus, eukaryotic cells show a higher level of organisation than prokaryotic cells.
Question 4. Describe the structure and functions of the nucleus.
Answer: The nucleus is a prominent organelle present in eukaryotic cells. It acts as the control centre of the cell. The nucleus is surrounded by a double-layered nuclear membrane that has pores. These pores allow materials to move between the nucleus and cytoplasm. Inside the nucleus, there is a dense round body called the nucleolus.
The nucleus contains chromatin material, which condenses to form chromosomes during cell division. Chromosomes contain DNA and proteins. DNA carries hereditary information, and its functional segments are called genes. Through genes, characters are passed from parents to offspring.
The main function of the nucleus is to control all activities of the cell, such as growth, metabolism, and reproduction. It also stores and protects genetic information. Thus, the nucleus is essential for the functioning and inheritance of the cell.
Question 5. Explain the structure and functions of mitochondria and plastids.
Answer: Mitochondria are double-membrane-bound organelles present in eukaryotic cells. The outer membrane is smooth, while the inner membrane is folded into finger-like projections called cristae. These folds increase surface area for chemical reactions. Mitochondria release energy from food through cellular respiration and store it in the form of ATP. This is why they are called the powerhouse of the cell.
Plastids are membrane-bound organelles found mainly in plant cells. Chloroplasts contain chlorophyll and perform photosynthesis. Chromoplasts contain coloured pigments other than chlorophyll and give bright colours to flowers and fruits. Leucoplasts are colourless and store food such as starch, oils, or proteins.
Both mitochondria and chloroplasts have their own DNA and ribosomes. Mitochondria help release energy, while chloroplasts help prepare food. Together, they play major roles in the life of plant cells.
Question 6. Explain the functions of endoplasmic reticulum, Golgi apparatus, and ribosomes.
Answer: The endoplasmic reticulum, Golgi apparatus, and ribosomes work together in the manufacturing and transport system of the cell. Ribosomes are tiny structures that are the sites of protein synthesis. They may be found freely in the cytoplasm or attached to the rough endoplasmic reticulum.
The endoplasmic reticulum is a network-like organelle spread throughout the cytoplasm. Rough endoplasmic reticulum has ribosomes on its surface and is involved in protein synthesis and secretion. Smooth endoplasmic reticulum lacks ribosomes and helps in the synthesis and storage of lipids and some hormones.
The Golgi apparatus is made up of stacks of flattened sacs. It receives proteins and lipids from the ER, modifies them, sorts them, packages them into vesicles, and sends them to different parts of the cell or outside it. Thus, ribosomes make proteins, ER helps in synthesis and transport, and Golgi apparatus packages and dispatches materials.
Question 7. What are lysosomes and vacuoles? Explain their functions.
Answer: Lysosomes are small membrane-bound sacs filled with digestive enzymes. They break down unwanted proteins, fats, carbohydrates, foreign particles, and damaged cell organelles. In this way, lysosomes keep the cell clean and healthy. They are therefore called the clean-up system of the cell.
Vacuoles are storage sacs present in cells. In mature plant cells, there is usually one large central vacuole filled with cell sap. It stores water, minerals, sugars, and waste materials. The vacuole also helps maintain pressure inside the cell and keeps the plant cell firm. This is why plants wilt when they do not get enough water.
In animal cells, vacuoles are smaller and usually used for temporary storage. Both lysosomes and vacuoles are important, but lysosomes mainly digest materials while vacuoles mainly store them.
Question 8. Explain mitosis and meiosis. Give their importance.
Answer: Cell division is the process by which new cells are formed from pre-existing cells. There are two major types of cell division: mitosis and meiosis.
Mitosis is the division in which one parent cell divides to form two genetically identical daughter cells. The daughter cells have the same number of chromosomes as the parent cell. Mitosis is important for growth, repair of damaged tissues, replacement of worn-out cells, and asexual reproduction.
Meiosis is a special type of cell division that occurs in reproductive organs to form gametes. In this process, one parent cell divides twice to form four daughter cells. Each daughter cell has half the number of chromosomes of the parent cell. Meiosis is important for sexual reproduction and creates genetic variation among offspring.
Thus, mitosis maintains chromosome number and helps body growth, while meiosis reduces chromosome number and helps reproduction.
Question 9. Explain the Cell Theory and its importance.
Answer: Cell Theory is one of the most important principles of biology. It was developed through the work of Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. Schleiden stated that all plants are made of cells. Schwann stated that all animals are made of cells. Virchow added that all cells arise from pre-existing cells.
According to Cell Theory, all living organisms are made up of one or more cells. The cell is the basic unit of structure and function in living beings. All new cells come from pre-existing cells.
The importance of Cell Theory is that it unifies biology. It shows that all living organisms, from bacteria to humans, are based on the same fundamental unit. It also explains growth, reproduction, repair, and continuity of life through cell division. This theory forms the foundation of modern biology.
Question 10. Explain how normal cells differ from cancer cells.
Answer: Normal cells grow, divide, perform their functions, and die in a controlled way. They divide only when needed, remain in the proper place, and stop dividing when they come in contact with neighbouring cells. This process is called contact inhibition. Dead or damaged cells are replaced by new healthy cells.
Cancer cells are abnormal cells that lose this control. They continue dividing uncontrollably and do not respond properly to signals that stop growth. As a result, they form masses of cells called tumours. Some tumours are harmless, but cancerous tumours may invade nearby tissues and spread to other parts of the body.
Thus, the main difference is that normal cells show controlled growth, while cancer cells show uncontrolled growth. Contact inhibition helps prevent tumour formation in normal animal cells.
