NCERT Solutions for Class 8 Science Chapter 8 Cell Structure and Functions Questions and Answers
Q.1 Indicate whether the following statements are True (T) or False (F).
- Unicellular organisms have a one-celled body.
- Muscle cells are branched.
- The basic living unit of an organism is an organ.
- The amoeba has an irregular shape.
Q.2 Make a sketch of the human nerve cell. What function do nerve cells perform?
Solution:- This is the type of cell which receives and transfers appropriate messages from the body to the brain, it also controls and harmonizes the working of different parts of the body.
Sketch of human nerve cell
Q.3 Writes short notes on the following.
- Nucleus of a cell
Cytoplasm– Is a fluid-like substance. It is present inside the cell membrane. It is also known as the home of cell organelles, also all the chemical reaction takes place in it. It carries several types of organelles like mitochondria, Golgi bodies, ribosomes etc.
Nucleus of a cell- It is a control center of the cells. It is rich in RNA and DNA. It is spherical and can be stained and can be seen easily with the help of a microscope. It controls all cellular activity and is responsible for the transmission of genetic information from one generation to the next. It is separated from the cytoplasm by a membrane called a nuclear membrane. The nucleus contains a dense spherical part called the nucleolus. There is a thread-like structure present in the nucleus called chromosomes. They carry the genes, which help in the transfer of characteristics from the parents to the offspring. Chromosomes are noticed only when the cells divide.
Q.4 Which part of the cell contains organelles?
Solution:- Cytoplasm is Known as the home of cell organelles and carries several organelles.
Q.5 Make sketches of animal and plant cells. State three between them.
Solution:- The differences between animal cells and plant cells are as follows:-
|Animal cells||Plant cells|
|I. They lack a cell wall||I. The cell wall is present and located outside the cell membrane. It is made up of cellulose.|
|II. It is irregular and round in shape, it is smaller than the plant cell.||II. It is rectangular or cubed in shape, It is larger than the animal cell.|
|III. Animal cells lack plastids.||III. Plastids are present in the plant cell. They make the leaves, flowers, or fruit present on the plant colorful or colourless.|
|IV. In this vacuoles are either absent or may be present in the small and more than 5 or 6.||IV. A large vacuole is present in the center of the plant and is also known as cell sap.|
|V. Centrosomes are present in animal cells||V. Plant cells lack centrosomes.|
Sketch of plant cell
Sketch of animal cell
Q.6 State the difference between eukaryotes and prokaryotes.
|I. They are multicellular. (More than two cell organisms.)||They are Unicellular. (Single-celled organisms).|
|II. They have well defined and true nucleus present with a nuclear membrane.||II. Nucleus is present but without nuclear membrane.|
|III. Eu: true; karyon: nucleus.||III. Pro: primitive; karyon: nucleus.|
|IV. Example:- all organisms except bacteria and blue-green algae.||IV. Example:- bacteria and blue-green algae.|
Q.7 Where are chromosomes found in a cell? State their function.
Solution:- It refers to condensed chromatin material present in the nucleus. They carry genes that transfer information for inheritance characteristics from parents to the next generation.
Q.8 ‘Cells are the basic structural unit of living organisms. Explain.
Solution:- Cells are the basic structure of units of living organisms because there are a lot of cellular units to form tissue and many tissues form an organ and organs combine to form a complete body. So, the cell is the basic structural unit of living beings. All the basic functions for the survival of an organism take place inside the cell. So, they are called the basic structural unit of living organisms.
Q.9 Explain why chloroplasts are found only in plant cells?
Solution:- Chloroplasts are only found in plant cells because they are pigmented with a green colour. It helps in photosynthesis. This green pigment is called chlorophyll. It is very important for photosynthesis if it is not there photosynthesis can’t take place.
Q.10 Complete the crossword with the help of the clues given below.
- This is necessary for photosynthesis.
3. Term for component present in the
6. The living substance in the cell.
8. Units of inheritance present on the
- Green plastids.
- 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.