NCERT Class 8 Science Chapter 8 - Cell - Structure and Functions Extra Questions

Chapter 8 - Cell - Structure and Functions Extra Questions

Fill in the blank
1. Many chemical reactions take place in the
cytoplasm to keep the cell alive.
2. Centrioles help in
cell division.
3. Several organ systems together form a
living organism.
4. The longest cell in human body is
nerve cell.
5.
Mitochondria is the power house of the cell.
6. The nucleus and the cytoplasm together make up the
protoplasm.
7.
Chromoplast are organelles responsible for the colour other than green in plants.
8. The plastid that help prepare food for the plant are
chloroplasts.
9.
DNA passing hereditary characters to the next generation.
10.
Cell wall giving rigidity to the plant cell.

Answer the following:
11. What is cell?
Answer:
The cell is the basic structural and functional unit of life. All the living organisms are made up of living cells.

12. Who discovered the cells first and when?
Answer:
Robert Hooke discovered the cell in 1665 under a simple magnifying glass. The cell he observed was slice of cork which were dead cells. Cork is a bark of tree.

13. Why is a cell membrane important to a cell?
Answer:
The cell membrane gives shape to the cell, protects inner parts of the cell and allows movement of material in and out of the cell. In plant cells the cell membrane is covered by another thick covering called cell wall. Cell membrane is also known as plasma membrane. It is made up of lipoproteins that is fats and proteins.

14. Name two organelles present in plant cell but not present in an animal cell?
Answer:
Plastids and Vacuoles are 2 organelles that are present in plant cells not in animal cells.

15. What do you mean by protoplasm?
Answer:
Protoplasm is the living content in an organism. The nucleus and cytoplasm together make protoplasm.

16. What are the building blocks of life? Why are they so called?
Answer:
The cell is the basic structural, functional, and biological unit of all organisms. A cell is the smallest unit of life, also called 'building block of life' because cells multiply and differentiate to form a multicellular organism as well as give rise to new organisms by forming gametes or reproductive spores.

17. Differentiate between unicellular and multicellular organisms giving examples.
Answer:

Unicellular
• The organisms that are made up of only one cell are called unicellular.
• It consists of prokaryotes and eukaryotes.
• It is irregular in shape.
Example - Amoeba, Paramecium
Multicellular
• The organisms that are made up of many cells are called multicellular.
• It consists of only eukaryotes.
• It has a defined shape.
Example - Humans, Animals

18. Write the functions of nucleus and chromosome?
Answer:
Nucleus - The nucleus is a spherical body generally found in the centre of the cell. It controls and regulates the activities of the cell.
Chromosomes - Chromosomes are found in nucleus of the cell. They carry genes which help in inheritance the transfer of characters from parents to offspring.

19. What are the differences between animal cell and plant cell?
Answer:

Plant cell
• Cell wall is present.
• Plastids are present.
• Presence of larger vacuoles.
Animal cell
• Cell wall is absent
• Plastids are absent.
• Absence of vacuoles. If present smaller in size.

20. Why are cells of different shapes and sizes? Give suitable examples?
Answer:
Cells have different shapes because they perform different functions. Each cell has its own role to play in helping our bodies to work properly, and their shape help them in carrying out these functions effectively. Example: RBC are like doughnut to carry more haemoglobin, and to fit through small spaces.

Multiple Choice Questions
21. Which one of the following term is not a part of the nucleus?
a) Ribosome
b) Nucleolus
c) Chromosome
d) Gene
Answer:
a) Ribosomes

22. A suitable term for the various components of cells is
a) Tissue
b) Cell organelles
c) Chromosomes
d) Genes
Answer:
b) Cell organelles

23. Cell is discovered by
a) Robert Brown
b) Robert Hooke
c) John Mendal
d) Charse Darwin
Answer:
b) Robert Hooke

24. Green colour of leaves is due to presence of the pigment ___
a) Chloroplast
b) Ribosomes
c) Mitochondira
d) Chlorophyll
Answer:
d) Chlorophyll

25. The control unit of cell is
a) Cytoplasm
b) Cell wall
c) Nucleus
d) All of these
Answer:
c) Nucleus

26. Identify the correct statement about cells.
a) All the cells have nucleus.
b) Cells of an organ have similar structure.
c) Cells of a tissue have similar structure.
d) Shape of all types of cells is round.
Answer:
c) Cells of a tissue have similar structure.

27. Name the outer most boundary of the cell?
a) Nuclear membrane
b) Cytoplasm
c) Plasma membrane
d) None of the above
Answer:
c) Plasma membrane

28. The jelly like substance present inside the cell is known as
a) Cytoplasm
b) Ectoplasm
c) Nucleoplasm
d) Mitochondria
Answer:
a) Cytoplasm

29. Which of the following is not a cell?
a) Virus
b) Bacterium
c) Spermatozoa
d) RBC
Answer:
a) Virus

30. Living substance of cell is called __________.
a) Cytoplasm
b) Chromosomes
c) Nucleus
d) Protoplasm
Answer:
d) Protoplasm

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