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

NCERT Solutions for Class 8 Science Chapter 8 Cell Structure and Functions can be used for any purpose and are great for research and preparation for exams. We cover all the important concepts of Class 10 keeping in mind the CBSE guidelines mentioned in the curriculum.

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Chapter 8 Cell Structure and Functions Class 8 Science NCERT Solutions

Exercise

1. Indicate whether the following statements are True or False.
(a) Unicellular organisms have a one-celled body.
(b) Muscle cells are branched.
(c) The basic living unit of an organism is an organ.
(d) Amoeba has irregular shape.

Solution

(a) True
(b) False
(c) False
(d) True

2. Make a sketch of the human nerve cell. What function do nerve cells perform?

Solution

Nerve cells receive messages from one part of the body and transmit them to another part. Messages can be received and transmitted very rapidly by all cellular organisms through a coordinating system known as the nervous system.

3. Write short notes on the following:
(a) Cytoplasm
(b) Nucleus of a cell

Solution

(a) Cytoplasm is a jelly-like substance that fills the interior of cells and is responsible for many of their functions. The cytoplasm provides a medium in which metabolic reactions take place, allowing the cell to carry out its essential functions. It helps to maintain the shape and integrity of the cell. The cytoplasm also contains organelles such as mitochondria, endoplasmic reticulum, ribosomes, lysosomes, vacuoles, and peroxisomes. These organelles are responsible for carrying out specific cellular processes such as respiration and protein synthesis.

(b) The nucleus of a cell is an organelle that serves as the control center of the cell. It contains genetic material in the form of DNA, which is responsible for controlling the cell’s growth and development. The nucleus is surrounded by a double membrane called the nuclear envelope. This membrane separates the nucleus from other organelles within the cytoplasm and helps to regulate what substances enter and exit the nucleus. The nucleus plays a role in regulating gene expression, which determines how proteins are produced and used by the cell. It helps to coordinate communication between different parts of the cell.

4. Which part of the cell contains organelles?

Solution

Cytoplasm present between the cell membrane and the nucleus contains the various cell organelles.

5. Make sketches of animals and plant cells. State three differences between them.

Solution

Plant Cell	Animal Cell
Cell membrane is surrounded by an additional covering called cell wall.	Cell membrane is not covered by cell wall.
Plant cell contains chloroplasts.	Animal cell does not have chloroplasts.
Plant cells do not contain centrosome.	Animal cells contain centrosome.

6. State the differences between Prokaryotes and Eukaryotes.

Solution

Prokaryotic cell	Eukaryotic cell
Division of cell is simple.	Division of cell is complex.
Prokaryotic cell has single chromosomes contained within the nucleus.	Eukaryotic cell has multiple chromosome within the nucleus.
The cell is not well organized due to the absence of nuclear membrane.	The cell is well organized due to the presence of nuclear membrane.
The organisms with these kinds of cell are called prokaryotes, for example: bacteria and blue green algae.	The organisms with these kinds of cells are called eukaryotes for example: plants and animals, etc.
Nucleus is absent.	Nucleus is present.
They are usually unicellular.	They are usually multicellular.
The size of the cell vary from 1-10 μm.	The size of the cell vary from 10-100 μm.

7. Where are chromosomes found in a cell? State their function.

Solution

Chromosomes are found in the nucleus of a cell. Chromosomes carry genes and help in the inheritance i.e. transfer of characteristics from the parents to the offspring.

8. ‘Cells are the basic structural unit of living organisms’. Explain.

Solution

A living organism is composed of cells, just as bricks are arranged to build a building. Cells perform all the basic life functions of an organism. Each cell consists of a group of cells that perform a specific function. Different tissues combine to form an organ and different organs together form an organ system, which, in turn, forms an organism. Therefore, cells can be considered the basic structural unit of life.

9. Explain why chloroplasts are found only in plant cells.

Solution

Chloroplasts are green coloured plastids. Chlorophyll, the green pigment found in chloroplasts, traps solar energy and converts it into food through the process of photosynthesis.

10. Complete the crossword with the help of class given below:

Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Units of inheritance present on the chromosomes.

Down
1. Green plastids.
2. Formed by the collection of tissues.
4. It separates the content of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.

Solution