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Cell structure and functions



Long Answer Questions for class 8

Question 1.
Differentiate between prokaryotic and eukaryotic cells?
Answer

S.No. Prokaryotic cell Eukaryotic cell
1 They are primitive and incomplete cells They are advance and complete cells.
2 Do not have well defined nucleus (nucleiod) Have well defined nucleus (true nucleus)
3 Membrane bound cell organelles are absent. Membrane bound cell organelles are present.
4 Bacteria and Mycoplasma are prokaryotic cells. Animal cells and Plant cells are eukaryotic cells.

Question 2.
Write the functions of different types of plastids?
Answer
Plastids with green–coloured photosynthetic pigment (chlorophyll) are called chloroplasts. They are also called kitchen of a plant cell.
Leucoplasts are colourless plastids and store food in the form of starch and fat.
Plastids with pigments other than green are called chromoplasts. These plastids give the flowers and fruits their bright colours, which attracts insects and animals for pollination.
Question 3.
Name any two types of cells that are capable of changing their shape. How does this feature help them in their functions?
Answer
The two types of cells that are capable of changing their shape are:
(i) White blood cells (WBCs): The white blood cells present in our blood can change their shape. This helps them to kill germs by engulfing them.
(ii) Amoeba: Amoeba can change its shape with the help of pseudopodia that are projections of its body. The pseudopodia help the Amoeba to capture its food and move from one place to another.
Question 4.
Explain the relationship between organ and organ system?
Answer
Many tissues combine to form an organ that carries out a particular function. For example, various types of tissues form organs such as heart, kidney etc. Various organs working together to carry on life activities constitute an organ system. For example heart, arteries and veins work together to form circulatory system.
Question 5.
What are the lower levels of organization in multicellular organisms? Are these levels present in unicellular organisms? Answer
In a multicellular organism, the lower levels of organization are as follows: Cells → Tissues → Organs → Organ systems → Organism
No, these levels are not present in unicellular organisms because unicellular organism consists of single cell.

Practice questions:

1. What is cell?
2. State the key features of cell theory?
3. Who saw cells first and when?
4. Why is a cell membrane important to a cell?
5. Name two organelles present in plant cell but not present in an animal cell?
6. What do you mean by protoplasm?
7. What are the building blocks of life? Why are they so called?
8. Differentiate between unicellular and multicellular organisms?
9. What is cell division? Why it is necessary?
10. Write the functions of nucleus and chromosome?
11. What is function of ribosomes?
12. What are the differences between animal cell and plant cell?
13. Why are cells of different shapes and sizes? Give suitable example?
14. Why is lysosomes known as suicidal bag of the cell?
15. Draw a diagram of animal cell and plant cell?


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