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

We all know plants make their own food. But how? Plants can make food due to the presence of plant cell organelles called chloroplast. Animals do not contain chlorophyll and hence cannot make their own food. There is a difference between the cell structure of a plant and an animal.

In this chapter of NCERT solutions for class 8 science, students will learn how cells are the basic units of all life on Earth.

We will understand about cell and it types and how different assemblies of cells make up different organisms. We will learn about the sizes of cells and the subcellular structures.

Download PDF of NCERT Solutions for Class 8 Science Chapter 8 Cell Structure and Function

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

(a) Unicellular organisms have one-celled body.

Correct answer-(T)

The unicellular organisms are made up of one cell and this cell functions as their entire body. Bacteria, protozoa, algae and so on are unicellular organisms.

(b) Muscle cells are branched.

Correct answer- (F)

The muscle cells are unbranched cells. They are present as individual units and combine to form muscle tissue that relax and contract to move different parts of the body.

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

Correct answer-(F)

The most basic or fundamental unit of life for any living organism is the cell and not an organ. The cells form tissues and tissues form organ.

(d) Amoeba has irregular shape.

Correct answer- (T)

Amoeba has irregular shape which implies that it is not defined. Amoeba has a shape like a puddle of water. It is neither circular, cuboidal or of any other specific shape.

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

The nerve cells are characteristic of nervous system. They are highly specialised cells that function to transmit electrical and chemical messages from one part of the body to another. The neurons are present in brain and spinal cord and spread throughout the entire body to relay signals to bring about almost all functions of the body.

Question 3: Write short notes on the following.

(a) Cytoplasm: Cells contains a liquid matrix that contains cellular organelles. This viscous liquid is called cytoplasm. It is transparent and contains different proteins, electrolytes, ions, water and salts. Different substances inside the cell moves through this cytoplasm and it also helps to maintain a specific shape of the cell. The cytoplasm is contained by a membrane called plasma membrane or cell membrane.

(b) Nucleus of a cell: The brain is the master of the body, similarly nucleus is the master of the cell. It controls the functioning of different cell organelles and also stores the DNA (Deoxyribose Nucleic Acid) which is the genetic component of any organism and contains genes. It is present as a spherical body inside the cell which is surrounded by a nuclear membrane. Substances continuously move to and from the nucleus to the cytoplasm of the cell.

Question 4: Which part of the cell contains organelles?

The cytoplasm of the cell contains all the cellular organelles. It is a viscous liquid component in which the cellular organelles are suspended and remain stable at a position in the cell.

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

The three differences between animal and plant cell are as follows:

PLANT CELL	ANIMAL CELL
The plant cells contain a tough and rigid layer around the cell membrane called cell wall.	The animal cells lack any cell wall.
Plant cells contain plastids and the most important among them is chloroplast which performs photosynthesis.	Animals are heterotrophic so they do not have any chloroplasts in their cell.
The plant cells also contain large, central and prominent vacuoles that store water and maintain the water and ion balance inside the cell.	Vacuoles are usually not present in animal cell. In case they are found they are very small and not in the center of the cell.

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Question 6: State the difference between eukaryotes and prokaryotes.

Prokaryotes	Eukaryotes
The prokaryotes are the organisms that contain nuclear material but lacks any membrane around it.	Eukaryotes are the organisms that contain cells with very well formed nucleus containing a properly organised nuclear membrane.
Examples: bacteria, blue green algae.	Examples: animal cells, plant cells and so on.

Question 7: Where are chromsomes found in a cell? State their function.

The chromosomes are thick thread like structures that are present inside the nucleus. They are very important in providing different features to an organism because they contain genes that are carried from the parents of that organism. The genes are transferred from parents to children through chromsomes.

Question 8: Cells are the basic structural units of living organisms’. Explain.

The cells are the most fundamental entity that makes up all the living organisms on earth. The unicellular organisms are made entirely out of one cell. The multicellular organisms are made up of many cells. The cells form tissues, tissues form organs, organs make up organ systems and organ system form entire organism. So the complete organism is formed by coming together of cells.

Question 9: Explain why chloroplasts are found only in plant cells?

The plants cells contain unique organelles called plastids. The most important among these plastids is chloroplast. The chloroplast is green plastid because it contains green pigment called chlorophyll. This chlorophyll uses sunlight to form carbohydrates. Since this feature is only present in plants, so the chloroplasts are only found in green plants and some algae.

Question 10: Complete the crossword with the help of clues given below.

This is necessary for photosynthesis-Chlorophyll.

Term for component present in the cytoplasm-Organelles

The living substance in the cell- Protoplasm

Units of inheritance present on the chromsomes- Genes

DOWN

1. Green plastids - Chloroplast

2. Formed by collection of tissues - Organs

3. It separates the contents of the cell from the surrounding medium - Membrane

4. Empty structure in the cytoplasm - Vacuole

5. A group of cells - Tissues

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