NCERT Solutions for Class 8 Science Chapter 8 Cell Structure and Functions

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Cell Structure and Functions NCERT Solutions for Class 8 Science Chapter 8

Class 8 Science Chapter 8 Cell Structure and Functions Exercise Questions and Answers

Question 1.
Indicate whether the following statements are True (T) or False (F).

(a) Unicellular organisms have a one-celled body.
Answer:
True

(b) Muscle cells are branched.
Answer:
False

(c) The basic living unit of an organism is an organ.
Answer:
False

(d) Amoeba has an irregular shape.
Answer:
True

Question 2.
Make a sketch of a human nerve cell. What function, do nerve cells perform?
Answer:
The function of Nerve cells:
The nerve cell receives and transfers the messages, thereby helping to control and coordinate the working of different parts of the body.

Question 3.
Write short notes on the following

(1) Cytoplasm
Answer:
Cytoplasm: This is a jelly-like substance found between the nucleus and the cell membrane. Various other components or organelles of cells are present in the cytoplasm. It is made up of basic elements like C, H, O, and N. These are found in the form of substances like carbohydrates, proteins, and water. These substances are present in all the cells of every organism irrespective of size, shape, and whether they are unicellular or multicellular.

(2) The Nucleus of a cell
Answer:
The nucleus of a Cell: It is an important component of the living cell. It is generally spherical and located in the centre of the cell. It can be stained and seen easily with the help of a microscope/ Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus.

Question 4.
Which part of the cell contains organelles?
Answer:
The Cytoplasm contains organelles of the cell.

Question 5.
Make sketches of animal and plant cells. State three differences between them.
Answer:

Animal Cell	Plant Cell
The Cell wall is absent.	The Cell wall is present.
Plastids are absent.	Plastids are present.
Presence of a number of small vacuoles.	Presence of a large vacuole.

Question 6.
State the difference between eukaryotes and prokaryotes.
Answer:
Eukaryotes have a well-organized nucleus with a nuclear membrane while prokaryotes do not have this.

Question 7.
Where are chromosomes found in a cell? State their function.
Answer:
Chromosomes are found in the nucleus. The functions of chromosomes are to carry genes on them and to help to transfer the character from parents to the next generation.

Question 8.
‘Cells are the basic structural units of living organisms.’ Explain.
Answer:
Cells are assembled to make the body of every organism. There are millions of living organisms. They are of different shapes and sizes. Even an organism with billions of cells begins its life as a single cell which is a fertilized egg. The fertilized egg cell multiplies and the number of cells increases as development proceeds.
So, the cell is called the basic structural unit of living organisms.

Question 9.
Explain why chloroplasts are found only in plant cells?
Answer:
There are some coloured bodies found in the cytoplasm of the cell of tradescantia leaf. These coloured bodies are scattered in the cytoplasm of the leaf cells. These are called plastids. They are of different colours. Some of them contain a green pigment called chlorophyll. Green-colored plastids are called chloroplasts. They provide green colour to the leaves. So we know that chlorophyll is mostly found in a plant cell. Therefore chloroplasts are found in plant cells.

Question 10.
Complete the crossword puzzle with the help of clues given below.
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
8. The living substance in the cell.
8. Units of inheritance present on the chromosomes.
Down
1. Green plastids.
2. Formed by a collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm. 7. A group of cells.
Answer:

Class 8 Science Chapter 8 Cell Structure and Functions InText Questions and Answers

Question 1.
Can you list the basic functions carried out by all living organisms?
Answer:
Some of the basic functions carried out by all living organisms are :

1. Growth and development
2. Movement
3. Nutrition
4. Respiration
5. Excretion
6. Reproduction, etc.

8.2 Cell

Question 2.
A hen’s egg can be seen easily. Is it a cell or a group of cells?
Answer:
The egg of a hen represents a single cell and is big enough to be seen by the unaided eye.

Shape of Celt

Question 3.
What advantage does amoeba derive by changing shape?
Answer:
The change in shape is due to the formation of pseudopodia which facilitates amoeba in its movement and capturing food.

Question 4.
Can you guess, which part of the cell gives it shape?
Answer:
Cell membrane.

Size of Cell

Question 5.
Are the cells in an elephant larger than the cells in a rat?
Answer:
The size of the cells has no relation to the size of the body of the animal or plant. It is not necessary that the cells in the elephant be much bigger than those in a rat. The size of the cell is related to its function.

8.5 Parts of the Cell

Question 6.
I want to know why plant cells need cell walls?
Answer:
The Cell wall is an additional layer surrounding the cell membrane which is required by plants for protection. Plant cells need protection against variations in temperature, high wind speeds, atmospheric moisture, etc.

8.6 Comparison of Plant and Animal Cells

Question 7.
Let us tabulate the similarities and distinguishing features of plant and animal cells. Only a few features are mentioned. You may add more in Table 8.1 (Textbook Page 96).
Answer:

S.NO.	Part	Plant cell	Animal cell
1.	Cell membrane	Present	Present
2.	Cell wall	Present	Absent
3.	Nucleus	Present	Present
4.	Nuclear membrane	Present	Present
5.	Cytoplasm	Present	Present
6.	Plastids	Present	Absent
7.	Vacuole	Present	Present