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NCERT Solution for Class 9 Science Chapter 5 : The Fundamental Unit of Life

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The 5th chapter -The Fundamental Unit of Life is related to Biology and it is the first chapter dealing with Biology in your syllabus. This chapter teaches you about cells. The cell structure is also explained in this chapter. Both animal and plant cells are explained with elaborated diagrams. For this chapter as well, you will get all NCERT Solutions for Class 9 Science on Swiflearn.

NCERT Solution for Class 9 Science Chapter 5 includes Intext Exercise 1, 2, 3, and an NCERT exercise. It contains a total of 11 questions in its NCERT exercise. This chapter includes analysis and memory-based questions that you can practice to test and enhance your analysis skills and cognizance.

Ncert solutions

NCERT Solution for Class 9 Science Chapter 5 : The Fundamental Unit of Life Ex 5.1

Exercise 5.1
Who discovered cells and how?

Robert Hooke (1665), Robert hooked by Chance observed a slice of cork through a self-designed microscope. He observed that it contained many little compartments, like a honey comb, which he named as cells. However, Leeuwenhoek (1674) discovered the free living cells in pond water for the first time, by his improved microscope.

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

Some organisms like Amoeba are unicellular and have single celled body .The single cell of unicellular organism performs all the life process.
Multicellular organisms have many cells to perform different functions. The cell is structural unit of all living organism.. Each living cell performs certain basic functions that the characteristic of all living forms such as cellular respiration. All cell have same organelles, no matter that their function is. Thus cell is also the functional unit of life.

Exercise 5.2

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

When concentration of CO2 is more inside the cell than outside, CO2 diffuses from the cell to outside of cell. If CO2 concentration inside the cell is less, CO2 moves inside the cell from outside. The water more in and out of the cell by the process of osmosis. Osmosis is the passage of water from a region of high water concentration through semi-permeable membrane cell membrane) to a
region of low concentration of water.

Why is the plasma membrane called selectively permeable membrane ?

Plasma membrane permits the entry and exit of some materials in the cell while it also prevents movement of some other materials. So , it is called selectively permeable membrane.

Fill in the gaps in the following table illustrating differences between
prokaryotic and eukaryotic cells.
Prokaryotic Cell Eukaryotic cell
1.Size : generally small 1. Size : generally large (5-100 pm)
2. Nuclear region: …….. 2. Nuclear region: well. Defined and
surrounded and known as by a nuclear membrane.
3.Chromosome : single 3. More than one chromosome
4. Membrane-bound cell organelles

Solution: Refer pdf.

Exercise 5.2.5

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

(i) Mitochondria (ii) Plastid (Chloroplast).

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

Each cell has got certain specific cell organelles. Each cell organelle performs a special function, e.g., making of new material removal waste from the cell, release of energy etc. If the organization of a cell is destroyed, the functioning of the cell organelle will be disturbed, control of the nucleus will be lost, ultimately.

Why are lysosome known as suicide bags?

A Lysosome is membrane bound bag like which contains powerful enzymes. If lysosome burst, Its enzymes eat no digest) other organellsits own cell. Therefore, that are known as ‘suicide bags’.

Where are proteins synthesised inside the cell?


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

Solution: Refer pdf.

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

Rutture of the Membrane let loose the cell contents of the cell and disintegrates the cell.

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

Golgi apparatus package wand dispatch enzymes, hormones and other essential .proteins and lipids secreted by E-R to target inside and outside the cell. The digestive enzymes which remain concealed in lysosome, will remain free in the cytoplasm killing the other cell content. Over all, in absence of Golgi apparatus cell would die.

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

Mitochondria are known as ‘Power House’ of the cell. They are said so because, the energy required for various life activities is released by mitochondria in he form of ATP molecules. The body uses energy stored in ATP for synthesis of new compounds and for mechanical work. AsATP instantlyprovide energy, they are called enemy currencya e cell.

Where do the lipids and proteins constituting the cell membrane get

Rough Endoplasmic Reticulum (RER)-synthesize proteins constituting cell membrane. Smooth Endoplasmic Reticulum (SER) -secrete lipids constituting cell membrane.

How does an Amoeba obtain its food?

Amoeba has flexible cell membrane. It enables amoeba to engulf in food by the process called endocytosis.

What is osmosis?

The passage of water from a region of its high concentration through a semipermeable membrane to a region oflow water concentration is known as osmosis.

Carry out the following osmosis experiment. Take four peeled halves and scoops 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 through containing water. Now,
(i) Keep cup A empty
(ii) Put one teaspoon sugar in cup B
(ii) Put one teaspoon salt in cup C
(iv) Put one teaspoon sugar in boiled potato cup D.
(v) Keep these for two hours. Then observe the four potato cups and answer the following:
(a)Explain why water gathers in the hollowed portion of B and C?
(b)Why is potato A necessary for this experiment?
(c) Explain why water does not gather in the hollowed out portions of A and D.

(a) Water gathers in the hollowed portion of potato B and C because:
(i) Living plasma membrane of potato cup act as semipermeable membrane.
(ii) There is higher concentration of water in through than the sugar solution of B and salt solution of C potato cup respectively.
(iii) So, by process of osmosis water moves into potato cups B and C.
(b) Potato cup A is kept empty to act as control. This shows that osmosis occurs only when a solution with low concentration of water is separated by semipermeable cell membrane from the region of higher concentration of water.
(c) (i) In the potato cup A, there is no solution to cause osmosis to occur.
(ii) In the potato cup D, the potato Cell membrane lost quality of semi permeability due to boiling. So, no water movement occurs from the through water into the potato Cup D.

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