5. The Fundamental Unit of Life Class 9 NCERT Exemplar Solutions Chapter 1 (CBSE Science)
CBSE Class 9 Science Chapter 5: The Fundamental Unit of Life – NCERT Exemplar Questions with Answers
Chapter 5: The Fundamental Unit of Life
Multiple Choice Questions
1. Which of the following can be made into crystal?
(a) A Bacterium (b) An Amoeba (c) A Virus (d) A Sperm
Answer: (c) A Virus
[ Viruses can be crystallized while bacterium Amoeba and sperm are living cellular entities that cannot be crystallized.]
2. A cell will swell up if
(a) The concentration of water molecules in the cell is higher than the concentration of water molecules in surrounding medium
(b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell
(c) The concentration of water molecules is same in the cell and in the surrounding medium
(d) Concentration of water molecules does not matter
Answer: (b) The concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell
[ This is a hypotonic condition. Water enters the cell by osmosis and causes it to swell up.]
3. Chromosomes are made up of
(a) DNA (b) protein (c) DNA and protein (d) RNA
Answer: (c) DNA and protein
[ Chromosomes are composed of DNA wrapped around proteins called histones. ]
4. Which of these options are not a function of Ribosomes?
(i) It helps in manufacture of protein molecules
(ii) It helps in manufacture of enzymes
(iii) It helps in manufacture of hormones
(iv) It helps in manufacture of starch molecules
(a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (iv) and (i)
Answer: (d) (iv) and (i)
[ Ribosomes do not make starch. They are involved in protein synthesis including enzymes and some protein-based hormones.]
5. Which of these is not related to endoplasmic reticulum?
(a) It behaves as transport channel for proteins between nucleus and cytoplasm
(b) It transports materials between various regions in cytoplasm
(c) It can be the site of energy generation
(d) It can be the site for some biochemical activities of the cell
Answer: (c) It can be the site of energy generation
[The endoplasmic reticulum (rough and smooth) is involved in protein transport material transport in cytoplasm and biochemical activities such as lipid synthesis and detoxification but energy generation (ATP production) occurs in mitochondria and not in the endoplasmic reticulum.]
6. Following are a few definitions of osmosis
Read carefully and select the correct definition
(a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane
(b) Movement of solvent molecules from its higher concentration to lower concentration
(c) Movement of solvent molecules from higher concentration to lower concentration of solution through a permeable membrane
(d) Movement of solute molecules from lower concentration to higher concentration of solution through a semipermeable membrane
Answer: (a) Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane .
7. Plasmolysis in a plant cell is defined as
(a) break down (lysis ) of plasma membrane in hypotonic medium
(b) shrinkage of cytoplasm in hypertonic medium
(c) shrinkage of nucleoplasm
(d) none of them
Answer: (b) Shrinkage of cytoplasm in hypertonic medium .
[ Plasmolysis is the shrinkage of cytoplasm in a hypertonic medium where water moves out of the cell causing the cytoplasm to pull away from the cell wall.]
8. Which of the following are covered by a single membrane?
(a) Mitochondria (b) Vacuole (c) Lysosome (d) Plastid
Answer: (b) Vacuole and (c) Lysosome .
[Vacuoles and lysosomes are both surrounded by a single membrane unlike mitochondria and plastids which have double membranes.]
9. Find out the false sentences
(a) Golgi apparatus is involved with the formation of lysosomes
(b) Nucleus, mitochondria and plastid have DNA; hence they are able to make their own structural proteins
(c) Mitochondria is said to be the power house of the cell as ATP is generated in them.
(d) Cytoplasm is called as protoplasm
Answer: (d) Cytoplasm is called as protoplasm
[ Cytoplasm is the jelly-like substance in a cell, but protoplasm includes both the cytoplasm and the nucleus.]
10. Find out the correct sentence
(a) Enzymes packed in Lysosomes are made through RER (rough endoplasmic reticulum)
(b) Rough endoplasmic reticulum and smooth endoplasmic reticulum produce lipid and protein respectively
(c) Endoplasmic reticulum is related with the destruction of plasma membrane
(d) Nucleoid is present inside the nucleoplasm of eukaryotic nucleus
Answer: (a) Enzymes packed in Lysosomes are made through RER (rough endoplasmic reticulum)
[ Enzymes (proteins) for lysosomes are synthesized by ribosomes on the rough ER . ]
11. Which cell organelle plays a crucial role in detoxifying many poisons and drugs in a cell?
(a) Golgi apparatus (b) Lysosomes (c) Smooth endoplasmic reticulum (d) Vacuoles
Answer: (c) Smooth endoplasmic reticulum
[ Smooth endoplasmic reticulum (especially in liver cells) detoxifies poisons and drugs.]
12. The proteins and lipids, essential for building the cell membrane, are manufactured by
(a) rough endoplasmic reticulum (b) golgi apparatus (c) plasma membrane (d) mitochondria
Answer: (a) rough endoplasmic reticulum
[ Proteins for the cell membrane are synthesized by the rough endoplasmic reticulum (RER) and lipids are synthesized by the smooth ER. Both are essential for building the membrane.]
13. The undefined nuclear region of prokaryotes are also known as
(a) nucleus (b) nucleolus (c) nucleic acid (d) nucleoid
Answer: (d) nucleoid
[ The undefined nuclear region in prokaryotes (where DNA is present without a true nuclear membrane) is called nucleoid. ]
14. The cell organelle involved in forming complex sugars from simple sugars are
(a) endoplasmic reticulum (b) ribosomes (c) plastids (d) golgi apparatus
Answer: (d) golgi apparatus
[ The Golgi apparatus forms complex sugars from simple sugars and packages them. ]
15. Which out of the following is not a function of vacuole?
(a) Storage (b) Providing turgidity and rigidity to the cell (c) Waste excretion (d) Locomotion
Answer: (d) Locomotion
[Vacuoles function in storage and provide turgidity or rigidity to the cell and help in waste excretion. They are not involved in locomotion.]
16. Amoeba acquires its food through a process, termed
(a) exocytosis (b) endocytosis (c) plasmolysis (d) exocytosis and endocytosis both
Answer: (b) endocytosis
[ Amoeba acquires its food by endocytosis specifically phagocytosis by engulfing food particles with its pseudopodia.]
17. Cell wall of which one of these is not made up of cellulose?
(a) Bacteria (b) Hydrilla (c) Mango tree (d) Cactus
Answer: (a) Bacteria
[ The cell wall of bacteria is made of peptidoglycan and not cellulose while Hydrilla mango tree and cactus which are plants have cell walls made of cellulose.]
18. Silver nitrate solution is used to study
(a) endoplasmic reticulum (b) golgi apparatus (c) nucleus (d) mitochondria
Answer: (b) golgi apparatus
[ Silver nitrate solution is used (by Camillo Golgi) to stain and study the Golgi apparatus in cells. ]
19. Organelle other than nucleus, containing DNA is
(a) endoplasmic reticulum (b) golgi apparatus (c) mitochondria (d) lysosome
Answer: (c) mitochondria
[ Mitochondria (and chloroplasts in plant cells) are the organelles other than the nucleus that contain their own DNA. ]
20. Kitchen of the cell is
(a) mitochondria (b) endoplasmic reticulum (c) chloroplast (d) golgi apparatus
Answer: (a) Mitochondria .
[Mitochondria are called the “kitchen” of the cell because they produce energy by breaking down food. ]
21. Lipid molecules in the cell are sythesized by
(a) smooth endoplasmic reticulum (b) rough endoplasmic reticulum (c) golgi apparatus (d) plastids
Answer: (a) smooth endoplasmic reticulum
[ Lipid molecules (like phospholipids and steroids) in the cell are mainly synthesized by the smooth endoplasmic reticulum (SER).]
22. Cell arises from pre-existing cell was stated by
(a) Haeckel (b) Virchow (c) Hooke (d) Schleiden
Answer: (b) Virchow
[ Rudolf Virchow (1855) famously modified the cell theory by stating “Omnis cellula-e cellula,” meaning all cells arise from pre-existing cells.]
23. Cell theory was given by
(a) Schleiden and Schwann (b) Virchow (c) Hooke (d) Haeckel
Answer: (a) Schleiden and Schwann
[ They proposed that all living things are made of cells. ]
24. The only cell organelle seen in prokaryotic cell is
(a) mitochondria (b) ribosomes (c) plastids (d) lysosomes
Answer: (b) Ribosomes
[ Prokaryotic cells don’t have membrane-bound organelles, but ribosomes are present for protein synthesis. ]
25. Organelle without a cell membrane is
(a) ribosome (b) golgi apparatus (c) chloroplast (d) nucleus
Answer: (a) Ribosome
[ It is a non-membrane-bound organelle, unlike Golgi, chloroplast and nucleus which have membranes.]
26. 1 μm is
(a) 
(b) 
(c) 
(d) 
Answer: (a) 
.
[ 1 micrometer (μm) 
. ]
27. Lysosome arises from
(a) endoplasmic reticulum (b) golgi apparatus (c) nucleus (d) mitochondria
Answer: (b) Golgi apparatus
[Lysosomes are formed by the Golgi bodies which package digestive enzymes into small vesicles.]
28. Living cells were discovered by
(a) Robert Hooke (b) Purkinje (c) Leeuwenhoek (d) Robert Brown
Answer: (c) Leeuwenhoek
[ He first observed living cells like bacteria and protozoa under his microscope. ]
29. Select the odd one out
(a) The movement of water across a semi permeable membrane is affected by the amount of substances dissolved in it.
(b) Membranes are made of organic molecules like proteins and lipids
(c) Molecules soluble in organic solvents can easily pass through the membrane.
(d) Plasma membranes contain chitin sugar in plants
Answer: (d) Plasma membranes contain chitin sugar in plants.
[Plant cell walls and not plasma membranes contain cellulose and not chitin. Plasma membranes are made of proteins and lipids and control the movement of substances.]
Short Answer Questions
30. Why are lysosomes known as ‘suicide-bags’ of a cell?
Answer: Lysosomes are called “suicide-bags” of the cell because they contain powerful digestive enzymes. When the cell gets damaged or disturbed lysosomes may burst and release these enzymes which digest and destroy their own cell. Hence they are known as suicide-bags of the cell.
31. Do you agree that “A cell is a building unit of an organism”. If yes, explain why?
Answer: Yes, a cell is a building unit of an organism because all living organisms are made up of cells and cells perform all the basic functions of life.
32. Why does the skin of your finger shrink when you wash clothes for a long time?
Answer: The skin of your finger shrinks when you wash clothes for a long time because soapy water is more concentrated than the cells of your skin. Due to exosmosis water moves out of the skin cells causing them to shrink.
33. Why is endocytosis found in animals only?
Answer: Endocytosis is found in animals only because animal cells lack a rigid cell wall. The flexible cell membrane allows it to engulf food or other particles by folding inward. Plant cells have a hard cell wall that prevents such invagination.
34. A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.
Answer: The phenomenon responsible is exosmosis.
When a person takes a concentrated salt solution the surrounding medium inside the stomach becomes hypertonic with lower water concentration compared to the cells lining the stomach. As a result water moves out from the stomach cells into the salt solution causing the cells to shrink and get irritated. This triggers vomiting as a reflex action to expel the harmful concentrated solution.
35. Name any cell organelle which is non membranous.
Answer: A non-membranous cell organelle is the ribosome. It is made of RNA and proteins and is involved in protein synthesis.
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, aminoacids, fatty acids, glycerol etc. What mechanisms are involved in absorption of digested food and water?
Answer: The absorption of digested food takes place by diffusion and active transport. Glucose amino acids and some minerals are absorbed by active transport while fatty acids and glycerol are absorbed by diffusion. Water is absorbed by osmosis.
37. If you are provided with some vegetables to cook. You generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?
Answer: When salt is added during cooking the outside medium of the vegetable cells becomes hypertonic. As a result water moves out of the cells through osmosis. This process is called exosmosis. Hence the vegetables release water.
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.
Answer: (c) a and b both are correct.
In a hypotonic solution water enters the cells through osmosis. Both onion peel cells and RBCs swell. RBCs burst easily because they do not have a cell wall. Onion peel cells resist bursting due to the presence of a rigid cell wall.
39. Bacteria do not have chloroplast but some bacteria are photoautorophic in nature and perform photosynthesis. Which part of bacterial cell performs this?
Answer: Photosynthetic bacteria perform photosynthesis with the help of pigments present in their cell membrane. These pigments trap sunlight and help in the process of 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
Answer: (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.
Answer: Chloroplasts – Found in green parts of plants like leaves and young stems; they perform photosynthesis.
Chromoplasts – Found in coloured parts like petals, fruits, and flowers; they give red, yellow, or orange colour.
Leucoplasts – Found in non-green parts like roots, tubers, and seeds; they store starch, oils, or proteins.
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——
Answer: (a) Transporting channels of the cell → Endoplasmic Reticulum (ER)
(b) Power house of the cell → Mitochondria
(c) Packaging and dispatching unit of the cell → Golgi apparatus
(d) Digestive bag of the cell → Lysosome
(e) Storage sacs of the cell → Vacuoles
(f) Kitchen of the cell → Chloroplast
(g) Control room of the cell → Nucleus
43. How is a bacterial cell different from an onion peel cell?
Answer: A bacterial cell is a prokaryotic cell without a true nucleus and membrane-bound organelles. An onion peel cell is a eukaryotic plant cell with a well-defined nucleus and membrane-bound organelles. Bacterial cells are smaller and simpler than onion peel cells.
44. How do substances like carbon dioxide (CO₂ ) and water (H₂O) move in and out of the cell?
Answer: Substances like carbon dioxide move in and out of the cell by diffusion from a region of higher concentration to lower concentration. Water moves in and out of the cell through osmosis across the selectively permeable cell membrane.
45. How does amoeba obtain its food?
Answer: Amoeba obtains its food by endocytosis. It uses pseudopodia to surround and engulf the food particle forming a food vacuole. Digestive enzymes act on the food inside the vacuole and the digested food is absorbed by the cell.
46. Name the two organelles in a plant cell that contain their own genetic material and ribosomes.
Answer: The two organelles in a plant cell that have their own genetic material and ribosomes are:
(i) Mitochondria – generate energy for the cell.
(ii) Chloroplasts – carry out photosynthesis.
47. Why are lysosomes also known as “scavengers of the cells”?
Answer: Lysosomes are known as "scavengers of the cells" because they contain powerful digestive enzymes that break down foreign invaders like bacteria and viruses as well as worn-out or damaged cell organelles. They clean the cell by removing unwanted materials and protecting it from harm. They can also digest the entire cell when it gets damaged.
48. Which cell organelle controls most of the activities of the cell?
Answer: The nucleus controls most of the activities of the cell. It contains chromosomes which carry genes and acts as the brain of the cell by directing functions such as growth metabolism and protein synthesis.
49. Which kind of plastid is more common in (a) roots of the plant (b) leaves of the plant (c) flowers and fruits
Answer: The common plastids in different plant parts are:
(a) Roots of the plant → Leucoplasts (store starch or other food)
(b) Leaves of the plant → Chloroplasts (carry out photosynthesis)
(c) Flowers and fruits → Chromoplasts (give colours like red, yellow, orange)
50. Why do plant cells possess large sized vacuole?
Answer: Plant cells have a large central vacuole to store water, nutrients, and waste. It helps maintain turgor pressure, which keeps the cell firm and supports the plant’s structure. It also aids in storage of pigments and defensive chemicals, and plays a role in cell growth by expanding the cell without using much energy.
51. How are chromatin, chromatid and chromosomes related to each other?
Answer: Chromatin chromatids and chromosomes are different forms of the same genetic material. Chromatin is the thin thread-like uncoiled DNA and protein present in the nucleus during interphase. When the cell prepares to divide chromatin condenses and thickens to form chromosomes. Each chromosome is made up of two identical strands called chromatids joined at the centromere. Thus chromatin forms chromosomes and each chromosome contains chromatids.
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.
Answer: (a) When a cell has higher water concentration than the surrounding medium, water moves out of the cell through osmosis. As a result, the cell shrinks.
(b) When a cell has low water concentration than the surrounding medium, water moves into the cell through osmosis. Due to this, the cell swells.
(c) When a cell and its surrounding medium have equal water concentration, there is no net movement of water. The cell remains unchanged.
Long Answer Questions
53. Draw a plant cell and label the parts which
(a) determines the function and development of the cell
(b) packages materials coming from the endoplasmic reticulum
(c) provides resistance to microbes to withstand hypotonic external media without bursting
(d) is site for many biochemical reactions necessary to sustain life.
(e) is a fluid contained inside the nucleus
Answer: The diagram of a plant cell is :
(a) Nucleus – determines the function and development of the cell
(b) Golgi apparatus – packages materials coming from the endoplasmic reticulum
(c) Cell wall – provides resistance to microbes and prevents bursting in hypotonic media
(d) Cytoplasm – site for many biochemical reactions
(e) Nucleoplasm – fluid contained inside the nucleus
54. Illustrate only a plant cell as seen under electron microscope. How is it different from animal cell?
Answer: Plant cell under electron microscope:
The difference between plant cell and animal cell is :
|
Plant Cell |
Animal Cell |
|
Cell wall is present. |
Cell wall is absent. |
|
Plastids are present. |
Plastids are absent. |
|
Vacuoles are large and permanent. |
Vacuoles are small or temporary. |
|
Shape is usually fixed and rectangular. |
Shape is usually irregular or rounded. |
55. Draw a neat labelled diagram of an animal cell.
Answer: The diagram of an animal cell is :
56. Draw a well labelled diagram of an eukaryotic nucleus. How is it different from nucleoid?
Answer: The diagram of an eukaryotic nucleus is
The difference between eukaryotic Nucleus and Nucleoid:
|
Nucleus |
Nucleoid |
|
Present in eukaryotic cells |
Present in prokaryotic cells |
|
Membrane-bound |
Not membrane-bound |
|
Contains chromatin and nucleolus |
Contains naked DNA |
|
Controls cell activities |
Controls cell activities indirectly |
57. Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?
Answer: The difference between Rough ER and Smooth ER is:
|
Rough ER |
Smooth ER |
|
Has ribosomes on its surface |
No ribosomes on its surface |
|
Involved in protein synthesis |
Involved in lipid synthesis and detoxification |
|
Helps in transport of proteins |
Helps in transport of lipids |
The endoplasmic reticulum produces lipids and proteins that are essential for making cell membranes, so it plays a key role in membrane formation and repair.
58. In brief state what happens when
(a) dry apricots are left for sometime in pure water and later transferred to sugar solution?
(b) a Red Blood Cell is kept in concentrated saline solution?
(c) the Plasma-membrane of a cell breaks down?
(d) rheo leaves are boiled in water first and then a drop of sugar syrup is put on it?
(e) golgi apparatus is removed from the cell?
Answer: (a) When dry apricots are kept in pure water, they absorb water by osmosis and swell up. When transferred to sugar solution, they lose water and shrink.
(b) When a Red Blood Cell is kept in concentrated saline solution, water moves out of the cell by osmosis and the cell shrinks.
(c) If the plasma membrane breaks down, substances inside the cell leak out and the cell dies.
(d) When rheo leaves are boiled first, the cells die and the plasma membrane loses its selective permeability. Therefore, no osmosis takes place after adding sugar syrup.
(e) If the golgi apparatus is removed, packaging and transport of materials inside the cell stop. Formation of lysosomes and secretion of substances are also affected.
59. Draw a neat diagram of plant cell and label any three parts which differentiate it from animal cell.
Answer: The diagram of plant cell :
Three parts that differentiate plant cell from animal cell:
(i) Cell wall – gives rigid shape and protection (absent in animal cells).
(ii) Chloroplasts – help in photosynthesis (absent in animal cells).
(iii) Large central vacuole – stores cell sap and maintains turgidity (small or absent in animal cells).
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