NCERT solution for class 9 science the fundamental unit of life ( Chapter 5)

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Solution for Exercise Questions

1. Make a comparison and write down ways in which plant cells are different from animal cells.

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Answer :

2. How is prokaryotic cell different from a eukaryotic cell?

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3. What would happen if the plasma membrane ruptures or breaks down?

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If plasma membrane ruptures or breaks down then molecules of some substances will freely move in and out of the cells and cell would die due to the disappearance of the protoplasmic material

4. What would happen to the life of a cell if there was no Golgi apparatus?

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Without the golgi apparatus, the cells will be disabled from packing and dispatching materials that were produced by the cells.

5. Which organelle is known as the powerhouse of the cell? Why?

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Mitochondria are known as the powerhouse of the cell because it releases the energy in the form of ATP(Adenosine triphosphate) molecules required for different activities of life.

6. Where do the lipids and proteins constituting the cell membrane get synthesised?

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Lipids and proteins are synthesised in the ER [Endoplasmic Reticulum].

7. How does an Amoeba obtain its food?

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Amoeba obtain its food by cell membrane which forms the food vacuole. The food vacuole contains the food items that the Amoeba has consumed.

8. What is osmosis?

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The process of movement of a water molecule from a region of higher concentration to a region of lower concentration through a semipermeable membrane is known as osmosis.

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.

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Answer :


(i) Water accumulates in the hollowed portions of B and C as a difference in the water concentration is observed. Therefore, osmosis will take place.

(ii) Potato A is essential in this experiment as it is significant to compare different scenarios seen in potato cups B, C and D.

(iii) Cup A didn't show any change in the concentration which is essential for osmosis. And cup D has dead cells thus there is no existence of a semipermeable membrane for water flow.

Solution for Intext Question

1. Who discovered cells, and how?

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Answer :

Cells were first discovered by Robert Hooke in 1665. He observed the cells in a cork slice with the help of a primitive microscope.

2. Why is the cell called the structural and functional unit of life?

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Cells form the structure of an entity. They perform all the fundamental activities independently. That's why are called the structural and functional unit of life.

1. How do substances like CO2 and water move in and out of the cell? Discuss.

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Both CO2 and H2O moves from higher concentration to lower concetration. The process for movement of CO2 is called diffusion and of H2O is called osmosis.

2. Why is the plasma membrane called a selectively permeable membrane?

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Plasma membrane is called as selectively permeable membrane because it only allows a certain molecules to pass through it.

1. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.

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1. Can you name the two organelles we have studied that contain their own genetic material?

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The two organelles that contain their own genetic material are:
1. Mitochondria

2. Plastids

2. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?

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If the organisation of a cell is destroyed due to some physical or chemical influence, then Lysosomes will burst and enzymes will digest such cells.

3. Why are lysosomes known as suicide bags?

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If the organisation of a cell is destroyed due to some physical or chemical influence, then Lysosomes will burst and enzymes will digest such cells. That's why are lysosomes known as suicide bags.

4. Where are proteins synthesised inside the cell?

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Answer :

Proteins are synthesised inside the cell in ribosomes, hence, are referred to as protein factories.