NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life, contains solutions to various questions in Exercises for Chapter 5. The Fundamental Unit of Life question answers Class 9 science have been explained in a simple and easy-to-understand manner. NCERT Solutions for Class 9Â help to check the concept you have learned from detailed classroom sessions and the application of your knowledge.
| Category | NCERT Solutions for Class 9 |
| Subject | Science |
| Chapter | Chapter 5 – The Fundamental Unit of Life |
Download NCERT Solutions for Class 9 Science Chapter 5 – The Fundamental Unit of Life
NCERT Solutions for Class 9 Science Chapter 5 the Fundamental Unit of Life Class 9 Question Answers
1. Who discovered cells, and how?
Answer.Â
Cells were discovered by Robert Hooke in 1665. He observed cells in a cork slice using a self-designed microscope. The cork slice resembled the structure of a honeycomb consisting of many compartments.Â
2. Why is the cell called the structural and functional unit of life?
Answer.
All living organisms are made up of cells, which perform various functions essential for the survival of the organism. Thus, a cell is called the structural and functional unit of life.
The Fundamental Unit of Life Class 9 Question Answers Page 61
1. How do substances like CO2Â and water move in and out of the cell? Discuss.
Answer.
CO2 and other gases move in and out of the cell by the process of diffusion. While, water moves across the cell by osmosis.
2. Why is the plasma membrane called a selectively permeable membrane?
Answer.
Plasma membrane is called selectively permeable membrane because it allows entry and exit of only some selected molecules through the cells. It also prevents the entry of some other molecules which may be harmful for the cell.
Class 9 Science Chapter 5 Question Answer Page 63
1. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.
Answer.
| Prokaryotic cell | Eukaryotic cell |
| Size: generally small (1-10µm) | Size: generally large (5-100µm) |
| Nuclear region: Poorly defined | Nuclear region: well defined and surrounded by a nuclear membrane |
| Chromosome: Single | More than one chromosome |
| Membrane bound cell organelles are absent. | Membrane bound cell organelles are present. |
The Fundamental Unit of Life Question Answers Page 65
1. Can you name the two organelles we have studied that contain their own genetic material?
Answer.
Mitochondria and Plastids are the two organelles we have studied that contain their own genetic material.
2. If the organization of a cell is destroyed due to some physical or chemical influence, what will happen?
Answer.
If the organization of a cell is destroyed, it will not be able to work properly and will die after some time with the help of enzymes provided by lysosomes.
3. Why are lysosomes known as suicide bags?
Answer.
Lysosomes contain powerful digestive enzymes. When a cell gets damaged, lysosomes may burst, and the enzymes digest their own cell. Hence, they are called ‘Suicide bags’.
4. Where are proteins synthesized inside the cell?
Answer.
Proteins are synthesized in the ribosomes of the cell attached to the rough endoplasmic reticulum, which are also known as ‘Protein factories’.
NCERT Solutions for Class 9 Science Chapter 5 Exercise:
1. Make a comparison and write down ways in which plant cells are also different from animal cells.
Answer.
| Plant cell | Animal cell |
| Cell wall is present outside the membrane. | Cell wall is absent. |
| They contain chloroplast. | They do not contain chloroplast. |
| A permanent large vacuole is present. | Vacuoles are many, small and temporary. |
| Larger in size than animal cells | Smaller in size than plant cells. |
| Nucleus is present in the side of a plant cell. | Nucleus is present in the center of animal cell. |
2. How is prokaryotic cell different from a eukaryotic cell?
Answer.
| Prokaryotic cell | Eukaryotic cell |
| Generally, small in size (1-10µm) | Generally large in size. (5-100µm) |
| Poorly developed nuclear region, no nuclear membrane. | Well defined nucleus, surrounded by nuclear membrane. |
| Nucleolus is absent. | Nucleolus is present. |
| Chromosome: Single | More than one chromosome is present. |
| Membrane bound cell-organelles are absent. | Membrane bound cell-organelles are present. |
| Centriole is absent. | Centriole is present in animals. |
| Cell division occurs by binary fission. | Cell division occurs by mitosis and meiosis. |
| It is found in bacteria and blue-green algae. | It is found in fungi, plants, and animals. |
3. What would happen if the plasma membrane ruptures or breaks down?
Answer.
If the plasma membrane of the cell ruptures or breaks down,
- The useful substances of the cell will move out as plasma membrane is selectively permeable.
- Transportation of substances in and out of the cells will be disturbed.
- Cell will loose its shape.
- Lysosomes will blast and release self-digesting enzymes and it will ultimately cause death of the cell.
4. What would happen to the life of a cell if there was no Golgi apparatus?
Answer.
Golgi apparatus performs the function of storage, modification and packaging of products in vesicles. If there was no golgi apparatus, cells would not be able to store, modify and dispatch proteins. Lysosome formation would also be affected as they are synthesized in golgi apparatus.
5. Which organelle is known as the powerhouse of the cell? Why?
Answer.
Mitochondria is called the powerhouse of the cell. It contains enzymes which oxidize the food and convert it into energy which is stored in the form of ATP (Adenosine Triphosphate). This ATP is broken down whenever energy is required for different activities of life.
6. Where do the lipids and proteins constituting the cell membrane get synthesised?
Answer.
The synthesis of lipids occurs in Smooth Endoplasmic Reticulum (SER). The proteins are synthesized in the ribosomes which are attached to the Rough Endoplasmic Reticulum( RER)
7. How does Amoeba obtain its food?
Answer.
Amoeba obtains its food through endocytosis. It is the process of ingestion of food through the plasma membrane, in which it forms finger-like projections called Pseudopodia and engulfs food from the surroundings.
8. What is osmosis?
Answer.
Osmosis is the process of diffusion of water molecules from a region of its higher concentration to its lower concentration through a semi-permeable membrane.
9. Carry out the following osmosis experiment:
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.
Answer.
i. Water gathers in the hollowed portion of B and C due to osmosis. In both the situations, the concentration of solute (sugar in B and salt in C) is higher inside the cup than water. Thus water flows from a region of its higher concentration to a region of its lower concentration.
ii. Potato A is necessary as it acts as the reference of control for the experiment and helps in comparing the results.
iii. Water does not gathers in the hallowed portion of A and D because
a) Hollowed portion of A is empty and no concentration difference, so no osmosis will occur.
b) Hollowed portion of D contains sugar but since boiling of potato causes destruction of the membrane so no osmosis will occur.
Topics Covered in The Fundamental Unit of Life Class 9 Science
- What are Living Organisms Made Up of?
- What is a Cell Made Up of? What is the Structural Organisation of a Cell?
- PLASMA MEMBRANE OR CELL MEMBRANE
- CELL WALL
- NUCLEUS
- CYTOPLASM
- CELL ORGANELLES
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