Chapter 5: The Fundamental Unit of Life

Why are lysosomes known as ‘suicide-bags’ of a cell?
Soln:
Lysosomes are the organelles that have digestive enzymes. When lysosomes burst, the digestive enzymes released start digesting its own cells. That is why they are known as suicidal bags.
31. Do you agree that “A cell is a building unit of an organism”? If yes, explain why?
Soln:
Yes, cells are the building unit of an organism. Cells performing similar functions join together to form tissues, which further forms organs and organ systems. This forms an organism. In a unicellular organism, a single cell performs all the life processes.
32. Why does the skin of your finger shrink when you wash clothes for a long time?
Soln:
Soap solution is hypertonic in nature which makes the water move out of the cells in your hand which results in shrinkage of fingers when you wash clothes for a long time.
33. Why is endocytosis found in animals only?
Soln:
Endocytosis is found only in animals because the cell wall is absent in animals. Due to this, the movement of substances inside the cell is easier in animals than in plants.
34. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.
Soln:
Upon consuming salt solution Osmosis process takes place which results in dehydration. This is the reason for vomiting of the person who consumes salt solution.
35. Name any cell organelle which is non-membranous.
Soln:
The ribosome is the only non-membranous cell organelle.
36. We eat food composed of all the nutrients like carbohydrates, proteins, fats, vitamins, minerals and water. After digestion, these are absorbed in the form of glucose, amino acids, fatty acids, glycerol etc. What mechanisms are involved in the absorption of digested food and water?
Soln:
Absorption and digestion involve diffusion and osmosis, respectively.
37. If you are provided with some vegetables to cook, you generally add salt to the vegetables during the cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?
Soln:
After adding salt, vegetables release water due to the process of osmosis. The addition of salt makes the external environment hypertonic. This means that the concentration of water outside is lowered as compared to the concentration of water inside the cell. This results in the elimination of water from the vegetables due to exosmosis.
38. If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for your answer.
(a) Both the cells will swell.
(b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.
(c) a and b both are correct.
(d) RBC and onion peel cells will behave similarly.
Soln:
(c) a and b both are correct.
Explanation:
When the surrounding medium is hypotonic water moves inside the cell. This leads to the swelling of cells. RBCs do not have a plasma membrane and they swell and burst easily. Plant cells have a cell wall which will prevent them from bursting.
39. Bacteria do not have chloroplast but some bacteria are photoautotrophic in nature and perform photosynthesis. Which part of the bacterial cell performs this?
Soln:
Small vesicles associated with plasma membrane are present in bacteria. These vesicles have pigment which can trap sunlight to carry photosynthesis.
40. Match the following A and B
(A) – (B)
(a) Smooth endoplasmic reticulum – (i) Amoeba (b) Lysosome – (ii) Nucleus (c) Nucleoid – (iii) Bacteria (d) Food vacuoles – (iv) Detoxification (e) Chromatin material – (v) Suicidal bag and nucleolus
Soln:
(A) – (B) (a) Smooth endoplasmic reticulum – (iv) Detoxification (b) Lysosome – (v) Suicidal bag and nucleolus (c) Nucleoid – (iii) Bacteria (d) Food vacuoles -(i) Amoeba (e) Chromatin material – (ii) Nucleus
41. Write the name of different plant parts in which chromoplast, chloroplast and leucoplast are present.
Soln:
Chromoplast is present in Flower and fruit Chloroplast is found in the leaves Leucoplast is present in the roots
42. Name the organelles which show the analogy written as under
(a) Transporting channels of the cell——
(b) Power house of the cell——
(c) Packaging and dispatching unit of the cell——
(d) Digestive bag of the cell——
(e) Storage sacs of the cell——
(f) Kitchen of the cell——
(g) Control room of the cell——
Soln:
Answers: a. Endoplasmic reticulum b. Mitochondria c. Golgi apparatus d. Lysosomes e. Vacuoles f. Chloroplast g. Nucleus
43. How is a bacterial cell different from an onion peel cell?
Soln:

44. How do substances like carbon dioxide (CO2) and water (H2O) move in and out of the cell?
Soln:
Substances like carbon dioxide (CO2) move in and out of the cell by diffusion, and water (H2O) move in and out of the cell through osmosis.
45. How does amoeba obtain its food?
Soln:
Amoeba obtains its food through endocytosis. It has finger-like projections that fuse with the food particle forming a food vacuole. The complex food particles are broken down into simpler ones inside the vacuole which are then diffused into the cytoplasm.
46. Name the two organelles in a plant cell that contain their own genetic material and ribosomes.
Soln:
Chloroplast and mitochondria are the two organelles in a plant cell that contain their own genetic material and ribosomes.
47. Why are lysosomes also known as “scavengers of the cells”?
Soln:
Lysosomes also are known as “scavengers of the cells” because lysosomes have lytic enzymes which are used to destroy pathogens and worn-out cells. Lysosomes also destroy waste materials which are harmful to the cell.
48. Which cell organelle controls most of the activities of the cell?
Soln:
Nucleus controls most of the activities of the cell.
49. Which kind of plastid is more common in
(a) roots of the plant
(b) leaves of the plant
(c) flowers and fruits
Soln:
Answers
a) Leucoplasts are more common in roots of the plant
b) Chloroplasts are more common in leaves of the plant
c) Chromoplasts are more common in flowers and fruits
50. Why do plant cells possess large-sized vacuole?
Soln:
Cells possess large-sized vacuole because vacuoles not only store important material but also contain a sap that gives turgidity to the cell.
51. How are chromatin, chromatid and chromosomes related to each other?
Soln:
Chromatin is the thread-like structure which forms the chromosomes. A copy of duplicated chromosome which is generally joined to the other copy by a centromere is called Chromatid.
Chromosomes: When a cell starts to divide, the tangled mass of chromatin condenses into long threads and finally, rod-like bodies called chromosomes.
52. What are the consequences of the following conditions?
(a) A cell containing higher water concentration than the surrounding medium
(b) A cell having low water concentration than the surrounding medium.
(c) A cell having equal water concentration to its surrounding medium.
Soln:
a) If a cell contains higher water concentration than the surrounding medium then the cell loses water and it shrinks. This process is called exosmosis. b) If a cell has low water concentration than the surrounding medium cell intakes water from the surroundings and the cell bursts. This process is called endosmosis. c) If A cell having equal water concentration to its surrounding medium then there will be no change in the cell.