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By Karan Singh Bisht
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Updated on 20 Sep 2025, 11:54 IST
Learn the entire cell chapter with clear, classroom-ready answers. Our NCERT Solutions are written by experienced subject experts and updated regularly to match the latest CBSE guidelines. Each question is broken down step-by-step definitions, diagrams, processes, and reasoning—so you understand how to solve, not just what to write. Perfect for quick revision, doubt-clearing, and exam prep.
This given PDF is a must-have for exam prep. It follows the CBSE syllabus and provides clear explanations with step-by-step solutions to every question. Use it to grasp the core concepts of motion and strengthen your performance in Class 9 Science.
Q. Who discovered the cell?
Ans. Robert Hooke (1665) while observing cork; later, Leeuwenhoek saw living cells (1674).
Q. State the cell theory.
Ans. All living organisms are made of cells; the cell is the basic structural and functional unit; all cells arise from pre-existing cells (Virchow).
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Q. Why is the cell called the fundamental unit of life?
Ans. Because all life processes occur inside cells, and tissues/organs are built from cells.
Q. Differentiate prokaryotic and eukaryotic cells.
Ans. Prokaryotes: no true nucleus, 70S ribosomes, few organelles. Eukaryotes: true nucleus, 80S ribosomes, membrane-bound organelles.
Q. Plant cell vs animal cell (two points).
Ans. Plant: cell wall, large central vacuole, plastids present. Animal: no cell wall/plastids, small vacuoles, centrioles present.
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Q. What is the plasma membrane?
Ans. A selectively permeable lipid bilayer with proteins; controls entry/exit of substances (fluid-mosaic model).
Q. Define diffusion with one example.
Ans. Movement of particles from higher to lower concentration; e.g., oxygen entering cells.
Q. Define osmosis and name its types.
Ans. Osmosis: movement of water through a semipermeable membrane from high to low water potential. Types: endosmosis (into cell), exosmosis (out of cell).
Q. What are hypotonic, isotonic, hypertonic solutions?
Ans. Hypotonic: lower solute—cell gains water; Isotonic: equal—no net change; Hypertonic: higher solute—cell loses water.
Q. What is plasmolysis?
Ans. Shrinking of cytoplasm and detachment of plasma membrane from cell wall in a hypertonic solution.
Q. What is deplasmolysis?
Ans. Recovery of a plasmolysed cell when placed in hypotonic water; turgidity returns.
Q. Describe the nucleus.
Ans. Bound by nuclear envelope; contains nucleoplasm, chromatin, nucleolus; controls activities and heredity.
Q. Define cytoplasm.
Ans. Jelly-like matrix between nucleus and membrane containing organelles and enzymes.
Q. Why are mitochondria called the powerhouse of the cell?
Ans. They synthesize ATP during respiration; double-membrane organelle with cristae and matrix, own DNA.
Q. Name types of plastids.
Ans. Chloroplasts (photosynthesis), chromoplasts (color), leucoplasts (storage).
ALso Check:
1. Who discovered cells and how?
Ans.
2. Why is the cell called the structural and functional unit of life?
Ans.
3. How do substances like CO2 and water move in and out of the cell ? Discuss.
Ans. Movement of substances like CO2 and water in and out of the cell occurs by the processes known as diffusion and osmosis respectively.
Movement of CO2 out of the cells (diffusion) :
4. Why is the plasma membrane called a selectively permeable membrane ? (or) State the reason for calling cell membrane as selectively permeable membrane.
A. Plasma membrane allows the movement of only some of the substances to pass through it. Hence, it is called a selectively permeable membrane.
5. Can you name the two organelles we have studied that contain their own genetic material ?
Ans.
6. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen ?
A . If the organisation of a cell is destroyed due to some physical or chemical influence then the cell may not acquire its structure and may not function properly and may lead to the destruction of the cell.
7. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.
| Prokaryotic Cell | Eukaryotic cell |
| i) Size: generally small (1-10 µm) 1 µm = 10-6m | i) Size: generally large (5-100 µm) |
| ii) Nuclear region: ________ and is known as ________. | ii) Nuclear region: well-defined and surrounded by a nuclear membrane. |
| iii) Chromosome: single. | iii) More than one chromosome. |
| iv) Membrane-bound cell organelles are absent. | iv) ……………………………………………………… ………………………………………………………. |
Ans.
| Prokaryotic Cell | Eukaryotic cell |
| i) Size: generally small (1-10 µm) 1 µm = 10-6m | i) Size: generally large (5-100 µm) |
| ii) Nuclear region: poorly defined because of the absence of a nuclear membrane, and is known as nucleoid. | ii) Nuclear region: well-defined and surrounded by a nuclear membrane. |
| iii) Chromosome: single. | iii) More than one chromosome. |
| iv) Membrane-bound cell organelles are absent. | iv) Membrane-bound cell organelles such as mitochondria, plastids, etc. are present. |
8. Why are lysosomes known as suicide bags ?
Ans.
9. Where are proteins synthesized inside the cell?
Ans. Proteins are synthesized in the Ribosomes of a cell.
10. Make a comparison and write down the ways in which plant cells are different from animal cells.
Ans.
| Plant cells | Animal cells |
| i) Plant cells are usually larger than animal cells. | i) Animal cells are generally small in size. |
| ii) Cell wall is present. | ii) Cell wall is absent. |
| iii) Plastids (chromoplasts and leucoplasts) are present. | iii) Except the protozoan Euglena, no animal cell possess plastids. |
| iv) Vacuoles are larger in size. | iv) Vacuoles are smaller in size |
11. How is a prokaryotic cell different from a eukaryotic cell ?
Ans.
| PROKARYOTIC CELL | EUKARYOTIC CELL |
| i) Size of the cell is generally small (0.5 – 5 µm). | i) Size of the cell is generally large (50 – 100 µm). |
| ii) Nuclear region is poorly defined due to the absence of a nuclear membrane. (Or) The cell lacks true nucleus. | ii) Nuclear region is well defined and is surrounded by a nuclear membrane. (Or) True nucleus is present. |
| iii) Membrane-bound cell organelles such as plastids, mitochondria, endoplasmic reticulum, golgi apparatus, etc. are absent. | iii) Cell organelles such as mitochondria plastids, endoplasmic reticulum, golgi apparatus, lysosomes, etc. are present. |
iv) It has 70S ribosomes. Eg : Bacteria and Blue green algae. | iv) It has 80S ribosomes. Eg : Cells of Fungi, Plants, Animals, etc. |
12. What would happen if the plasma membrane ruptures or breaks down ?
Ans. If the plasma membrane of a cell ruptures or beaks down, then the cell will die.
13. What would happen to the life of a cell if there was no Golgi apparatus ?
Ans. If there was no Golgi apparatus in the cell :
14. Which organelle is known as the powerhouse of the cell ? Why ?
Ans.
15. Where do the lipids and proteins constituting the cell membrane get synthesized?
Ans. Lipids and proteins constituting the cell membrane are synthesized in the Endoplasmic Reticulum (ER).
Ans.
17. What is osmosis ?
Ans. The process of movement of water molecules (solvent) from a region of high concentration to a region of low concentration through a selectively permeable membrane is called osmosis.
18. Carry out the following osmosis experiment :
Ans. Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
Keep these for two hours. Then observe the four potato cups and answer the following :
Ans.
As cell membranes of boiled potato are dead, osmosis does not occur and hence, water will not gather in hollow portion of potato cup ‘D’.
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You can download free PDFs from trusted platforms like Infinity Learn. NCERT textbooks are on ncert.nic.in; solutions are hosted by edtech sites such as Infinity Learn.
Read NCERT line-by-line, label all diagrams, make a glossary (diffusion, osmosis, plasmolysis), and practice endo/exocytosis flowcharts. Do 20–30 objective questions + 5 diagram questions. Retest weak terms with flashcards.
Cell theory; prokaryotic vs eukaryotic cells; plant vs animal cells; plasma membrane (diffusion/osmosis); cell wall and plasmolysis; nucleus (chromatin, chromosomes); cytoplasm; organelles—ER, Golgi, mitochondria, plastids, lysosomes, ribosomes; vacuoles; endocytosis/exocytosis; turgidity.
The fundamental unit of life is the cell. It is the basic structural and functional unit of all living organisms.
The two main types of cells are prokaryotic cells (without a defined nucleus) and eukaryotic cells (with a defined nucleus).