Table of Contents
Students can acquire comprehensive knowledge about the cell through the utilization of NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life. These NCERT solutions have been developed by experienced educators who possess expertise in their respective domains. Furthermore, we maintain a commitment to consistently updating the content pertaining to NCERT Solutions of Class 9 Science in accordance with the guidelines set forth by the CBSE board. Additionally, we offer a thorough breakdown of the questions, elucidating each step and process in a format that is easily comprehensible.
NCERT Solutions Class 9 Science Chapter 5 – CBSE Download Free PDF
Access answers to NCERT Class 9 Science Chapter 5 – The Fundamental Unit of Life
1. Who discovered cells and how?
Ans. i) Cells was first discovered in 1665 by an English botanist, Robert Hooke.
ii) He discovered cells by observing a cork slice under primitive microscope.
2. Why is the cell called the structural and functional unit of life?
Ans. i) A cell is the smallest unit of life and is capable of performing all living functions. Cells are the building blocks of life.
ii) This is the reason why cell is referred to as the basic structural and functional unit of life.
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) :
i) During respiration, continuous production of CO2 occurs inside the cell. This increases the amount of CO2 in the cytoplasm.
ii) Therefore, CO2 moves out of the cell (from a region of higher concentration towards a region of lower concentration).
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.
i) Mitochondria
ii) Plastids
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.
i) Lysosomes contain powerful digestive enzymes capable of breaking down all organic material.
ii) During the disturbance in cellular metabolism (for example, when the cell gets damaged, lysosomes may burst and the enzymes digest their own cell (destroy).
iii) Therefore, lysosomes are known as ‘suicide bags’ of a cell.
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 :
i) the processes such as storage, modification, and packaging of products and formation of lysosomes will not be possible.
ii) the formation of complex sugars from simple sugars will not be possible as this takes place with the help of enzymes present in Golgi bodies.
14. Which organelle is known as the powerhouse of the cell ? Why ?
Ans. i) Mitochondrion is known as the powerhouse of the cell.
ii) The energy required for various cellular activities is released by the mitochondrion in the form of ATP (Adenosine Triphosphate) molecules.
iii) Hence, mitochondrion is known as powerhouse of the cell.
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).
More Resources for Class 9
- NCERT Solutions for Class 9
- NCERT Solutions for Class 9 Maths
- NCERT Solutions for Class 9 Social Science
16.How does an Amoeba obtain its food ?
Ans.
i) The cell membrane in Amoeba is flexible.
ii) The flexibility of the membrane enables the cell to engulf food and other substances (foregin particles) from its external environment by endocytosis.
iii) Amoeba acquires its food by this process. This is called Endocytosis.
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,
a) Keep cup ‘A’ empty.
b) Put one teaspoon sugar in cup ‘B’.
c) Put one teaspoon salt in cup ‘C’.
d) Put one teaspoon sugar in the boiled potato cup ‘D’.
Keep these for two hours. Then observe the four potato cups and answer the following :
i) Explain why water gathers in the hollowed portion of ‘B’ and ‘C’.
ii) Why is potato ‘A’ necessary for this experiment?
iii) Explain why water does not gather in the hollowed-out portions of ‘A’ and ‘D’.
Ans. i) Water gathers in the hollowed portions of ‘B’ and ‘C’ because water enters the potato cups as a result of osmosis.
ii) Potato cup ‘A’ is necessary to know about the process of osmosis.
iii) Water does not gather in the hollowed-out portion of potato cup ‘A’ because it is empty. It is a control in the experimental setup.
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’.
| Check Subject-Wise Free Study Materials for Class 1 to 12 | |||
| Physics | Chemistry | Maths | Biology |
| Articles | |||
| Physics Articles | Chemistry Articles | Maths Articles | Biology Articles |
| Topics | |||
| Physics Topics | Chemistry Topics | Maths Topics | Biology Topics |
| Difference Between Articles | |||
| Difference Between Articles in Physics | Difference Between Articles in Chemistry Formulas | Difference Between Articles in Maths Formulas | Difference Between Articles in Biology Formulas |
| Formulas | |||
| Physics Formulas | Chemistry Formulas | Maths Formulas | |
