🔹 Very Short Answer (1 mark)
Q1. Who discovered the cell?
Ans. Robert Hooke in 1665.
Q2. Who proposed the cell theory?
Ans. Schleiden and Schwann.
Q3. Who discovered the nucleus?
Ans. Robert Brown.
Q4. What is the structural and functional unit of life?
Ans. Cell.
Q5. Name the smallest cell.
Ans. Mycoplasma.
Q6. Name the largest cell.
Ans. Ostrich egg.
Q7. What are prokaryotic cells?
Ans. Cells without a well-defined nucleus (e.g., bacteria).
Q8. Name the control center of the cell.
Ans. Nucleus.
Q9. What is the function of mitochondria?
Ans. It is the powerhouse of the cell, producing energy in the form of ATP.
Q10. Which organelle is responsible for photosynthesis?
Ans. Chloroplast.
🔹 Short Answer (2–3 marks)
Q11. What is cell theory?
Ans.
- All living organisms are made of cells.
- Cell is the structural and functional unit of life.
- All cells arise from pre-existing cells (added by Virchow).
Q12. Write two differences between prokaryotic and eukaryotic cells.
Ans.
- Prokaryotic: No true nucleus, smaller, e.g., bacteria.
- Eukaryotic: True nucleus present, larger, e.g., plant and animal cells.
Q13. Write the function of ribosomes.
Ans. Ribosomes are the protein factories of the cell.
Q14. Why is plasma membrane called selectively permeable?
Ans. Because it allows only certain substances to enter or leave the cell.
Q15. What is osmosis?
Ans. The movement of water molecules from a region of higher concentration to lower concentration through a semi-permeable membrane.
Q16. What is diffusion?
Ans. The free movement of molecules from higher to lower concentration until uniform distribution.
Q17. What is the role of endoplasmic reticulum (ER)?
Ans.
- Rough ER: Protein synthesis.
- Smooth ER: Lipid synthesis and detoxification.
Q18. What are chromosomes made of?
Ans. DNA and proteins.
Q19. Name the cell organelle responsible for intracellular digestion.
Ans. Lysosomes (“suicidal bags”).
Q20. Why is Golgi apparatus known as the secretory organelle?
Ans. Because it helps in packaging and transporting proteins and other materials.
🔹 Long Answer (4–5 marks)
Q21. Explain the structure of the plasma membrane.
Ans.
- Made of a phospholipid bilayer with embedded proteins.
- Selectively permeable.
- Controls movement of substances in and out.
Q22. Differentiate between plant and animal cells.
| Plant Cell | Animal Cell |
|---|---|
| Cell wall present | No cell wall |
| Plastids present | No plastids |
| Large central vacuole | Small vacuoles |
| Usually rectangular | Usually round/irregular |
Q23. Explain the three types of solutions in terms of osmosis.
Ans.
- Hypotonic: Water enters cell → cell swells.
- Hypertonic: Water leaves cell → cell shrinks.
- Isotonic: No net movement → cell remains same.
Q24. Write the functions of mitochondria.
Ans.
- Releases energy during respiration.
- Stores energy in ATP form.
- Helps in metabolic activities.
Q25. What are plastids? Write types.
Ans.
- Plastids are double-membrane organelles found in plant cells.
Types:
- Chloroplasts → photosynthesis.
- Chromoplasts → give colour.
- Leucoplasts → storage of starch, oil, proteins.
Q26. Why are lysosomes called suicidal bags?
Ans. Because they contain digestive enzymes that can destroy the cell if released.
Q27. Explain the structure and function of nucleus.
Ans.
- Nucleus has nuclear envelope, nucleoplasm, nucleolus, chromosomes.
- Functions: controls cell activities, stores genetic information, helps in cell division.
Q28. Write differences between rough ER and smooth ER.
| Rough ER | Smooth ER |
|---|---|
| Ribosomes present | No ribosomes |
| Protein synthesis | Lipid synthesis & detoxification |
Q29. What is the function of vacuoles?
Ans.
- Storage of food, water, waste.
- In plants, helps maintain turgidity.
Q30. Why are mitochondria called “powerhouse of the cell”?
Ans. Because they release energy by oxidising food and store it in the form of ATP.
🔹 Case Study / Application-Based (5–6 marks)
Q31. Case Study – Raisins in Water
Raisins swell when kept in water.
(i) Name the process.
(ii) Why does this happen?
Ans.
(i) Osmosis.
(ii) Water enters the raisins because concentration of water is higher outside.
Q32. Case Study – Plasmolysis in Plant Cells
When a plant cell is placed in concentrated sugar solution, it shrinks.
(i) What is this phenomenon called?
(ii) Why does it occur?
Ans.
(i) Plasmolysis.
(ii) Water moves out of the cell into hypertonic solution by osmosis.
Q33. Why are chloroplasts important for plants?
Ans. Because they contain chlorophyll, which absorbs sunlight for photosynthesis.
Q34. A cell has no cell wall, small vacuoles and lacks plastids. Is it plant or animal cell?
Ans. Animal cell.
Q35. Case Study – White Blood Cells
WBCs change shape and squeeze through walls of blood vessels.
(i) Which property does this show?
(ii) Which cell organelle helps them?
Ans.
(i) Amoeboid movement.
(ii) Cytoskeleton.
Q36. Why is the plasma membrane important for a cell?
Ans. Because it protects cell contents, allows entry/exit of substances, and maintains homeostasis.
Q37. Why do onion cells placed in salt solution shrink?
Ans. Due to exosmosis – water leaves the cell into concentrated solution.
Q38. Why do onion peel cells not burst in hypotonic solution but animal cells do?
Ans. Because onion cells have a rigid cell wall, which prevents bursting.
Q39. Which cell organelle is semi-autonomous and has its own DNA and ribosomes?
Ans. Mitochondria and chloroplasts.
Q40. How does the nucleus control cell activities?
Ans. By directing synthesis of proteins through DNA and RNA.
🔹 Extra Important (41–50)
Q41. Define protoplasm.
Ans. The living content of the cell (cytoplasm + nucleus).
Q42. Write one difference between chromatin and chromosomes.
Ans.
- Chromatin: Thin thread-like DNA in non-dividing cell.
- Chromosomes: Condensed DNA during cell division.
Q43. Write one difference between plant vacuole and animal vacuole.
Ans.
- Plant vacuole: Large and central.
- Animal vacuole: Small and temporary.
Q44. What is endocytosis?
Ans. The process of engulfing food or other material by the cell membrane.
Q45. Why is cell wall absent in animal cells?
Ans. To allow flexibility and different types of movement.
Q46. What is cytoplasm?
Ans. Jelly-like fluid between nucleus and cell membrane containing organelles.
Q47. Which organelle is known as “traffic police of the cell”?
Ans. Golgi apparatus (directs proteins and lipids).
Q48. Which organelle helps in cell division in animal cells?
Ans. Centrosome.
Q49. Which scientist coined the term ‘cell’?
Ans. Robert Hooke.
Q50. Why is cell called the fundamental unit of life?
Ans. Because all living beings are made of cells, and all functions (nutrition, respiration, excretion, reproduction) are carried out by cells.