CHAPTER 5
THE FUNDAMENTAL UNIT OF LIFE
LE SOLUTIONS
Very Short Answer Questions
1. 1. (i) Name the process by which an amoeba acquires its food from its surroundings.
Answer: Endocytosis. Amoeba engulfs food particles by forming pseudopodia, which enclose the
food in a vacuole where digestion occurs.
2. (ii) The digestive enzymes present in lysosomes are synthesized by which cell organelle?
Answer: Rough Endoplasmic Reticulum. These enzymes are first synthesized by ribosomes on
rough ER and then transported to lysosomes via the Golgi apparatus.
3. 2. What is the structural and functional unit of life?
Answer: Cell. It is the smallest unit that can carry out all the life processes like nutrition,
respiration, reproduction etc.
4. 3. Which type of plastid stores starch?
Answer: Leucoplast. These are colourless plastids found in storage organs like roots and store
starch, oils, or proteins.
5. 4. (a) The undefined nuclear region of prokaryotic cell
Answer: Nucleoid
6. (b) Site of energy release inside the cell
Answer: Mitochondria. It produces energy by aerobic respiration in the form of ATP.
7. (c) Energy currency of cell
Answer: ATP – Adenosine Triphosphate. It provides energy for various biochemical activities in
the cell.
8. 5. Why are plant cells more rigid than animal cells?
Answer: Due to the presence of a rigid cell wall made of cellulose which gives mechanical
strength and protection.
9. 6. Name two cell organelles that have their own DNA.
Answer: Mitochondria and Chloroplast. These organelles are semi-autonomous and can replicate
themselves.
10. 7. What is the difference between number and size of vacuoles in plant cells and animal cells?
Answer: Plant cells have a large central vacuole whereas animal cells have smaller and more
numerous vacuoles.
11. 8. Which cell organelle is involved in the production of lipids?
Answer: Smooth Endoplasmic Reticulum (SER). It also helps in detoxification and storage of
lipids.
12. 9. What are chromosomes made of?
Answer: DNA and proteins. DNA carries genetic information and proteins help in packaging it
into chromosomes.
13. 10. Name the only cell organelle seen in prokaryotic cell.
Answer: Ribosomes. They help in protein synthesis and are smaller than those in eukaryotic cells.
Short Answer Type Questions
14. 1. Why is the nucleus called the ‘control center of the cell’?
Answer: The nucleus is called the control center because it contains the cell's genetic material
(DNA) that directs all the cellular activities like growth, metabolism, protein synthesis, and cell
division.
15. 2. Why is endocytosis found in animals only?
Answer: Endocytosis requires a flexible cell membrane to engulf particles. Plant cells have rigid
cell walls which prevent membrane invagination, so endocytosis occurs only in animal cells.
16. 3. Why is the Golgi apparatus called the secretary organelle of the cell?
Answer: The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or
delivery to other organelles, hence called the secretary organelle.
17. 4. Why are bacteria, fungi, and plant cells able to withstand very dilute external medium
without bursting? How will they respond in a concentrated salt solution?
Answer: They have rigid cell walls that prevent bursting. In concentrated salt solutions, they
undergo plasmolysis where the cell membrane shrinks away from the cell wall.
18. 5. Differentiate between diffusion and osmosis.
Answer:
Diffusion: Movement of molecules from higher to lower concentration.
Osmosis: Movement of water through a semipermeable membrane from low to high solute
concentration.
19. 6. Differentiate between Nucleus and Nucleoid.
Answer:
Nucleus: Membrane-bound, found in eukaryotes.
Nucleoid: Not membrane-bound, found in prokaryotes.
20. 7. If cells of onion peel and RBC are separately kept in hypotonic solution, what will happen
to each of them? Explain the reason for your answer.
Answer: RBC will swell and may burst due to lack of cell wall. Onion peel cells will swell but
won’t burst due to presence of a rigid cell wall. Hence, both (a) and (b) are correct.
21. 8. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is
the phenomenon responsible for such situation? Explain.
Answer: Exosmosis. Salt draws out water from body cells, leading to cellular dehydration and
disturbance in functions, triggering vomiting as a response.
22. 9. Why lysosomes are known as suicidal bags?
Answer: Lysosomes contain powerful enzymes that can digest the entire cell if released. They
self-destruct when the cell is damaged, hence the name.
23. 10. How does cell division occur and what are the types of cell division?
Answer: Cell division occurs via mitosis (for growth and repair) and meiosis (for formation of
gametes). Mitosis produces identical cells, while meiosis reduces chromosome number by half.
Long Answer Type Questions
24. 1. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic
reticulum important for membrane biogenesis?
Answer:
Rough ER: Has ribosomes, synthesizes proteins.
Smooth ER: No ribosomes, synthesizes lipids.
Both contribute to membrane biogenesis by transporting proteins and lipids to the membrane.
25. 2. Draw a neat diagram of a plant cell. Label any three parts which differentiate it from
animal cell.
Answer:Differences: Cell wall, chloroplast, and large central vacuole are present in plant cells but
absent in animal cells.
26. 3. What will happen in the following conditions:
(a) Dry apricot in pure water then sugar solution
(b) Rheo leaves boiled then placed in sugar syrup
(c) Golgi apparatus removed
(d) Plasma membrane breaks down
(e) RBC in salt solution
Answer:
(a) Swells in water (endosmosis), shrinks in sugar (exosmosis)
(b) No plasmolysis as cells are dead
(c) Protein transport stops
(d) Cell dies
(e) Water leaves cell, causing shrinkage
27. 4. How is a bacterial cell different from an onion peel cell?
Answer:
Bacterial Cell: Prokaryotic, no nucleus or membrane-bound organelles.
Onion Peel Cell: Eukaryotic, has nucleus and membrane-bound organelles.
28. 5. Give five points of differences between plant cell and animal cell.
Answer:
1. Cell wall: Present in plant, absent in animal
2. Vacuole: Large central in plant, small/many in animal
3. Chloroplast: Present in plant
4. Shape: Regular in plant, irregular in animal
5. Centrioles: Present in animal, usually absent in plant
Case/Source Based Questions
29. 1. Why mitochondria are known as semiautonomous organelle?
Answer: Mitochondria have their own DNA and ribosomes and can replicate independently,
though they depend on the cell for some proteins.
30. 2. Name two organelles other than mitochondria having double membrane.
Answer: Nucleus and Chloroplast.
31. 3. Give reasons:
(i) mitochondria have largely folded inner membrane.
(ii) ATP is known as energy currency of the cell.
Answer:
(i) Folds (cristae) increase surface area for ATP synthesis.
(ii) ATP provides energy for all cell activities.
32. OR (i) Mitochondria is known as the power house of the cell.
(ii) Muscle cells have more mitochondria than skin cells.
Answer:
(i) Because they produce ATP.
(ii) Muscle cells require more energy for contraction, hence have more mitochondria.
