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प्रश्न
Write short notes on the following.
Nucleus of a cell
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उत्तर
Nucleus of a cell: The nucleus is a spherical structure generally present at the centre of a cell. The nucleus is composed of the following components:
1) Nuclear membrane: It is a double-layered membrane which separates the contents of the nucleus from the cytoplasm. The nuclear membrane has nuclear pores that allow the transfer of specific substances in and out of the nucleus.
2) Nucleolus: It is a small spherical body that is not bound by any membrane.
3) Chromosomes: These are thread-like structures that carry genes. Genes contain information necessary for the transfer of characteristics from the parents to the offspring. Thus, chromosomes play an important role in the inheritance of characteristics.
संबंधित प्रश्न
Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
- Keep cup A empty.
- Put one teaspoon of sugar in cup B.
- Put one teaspoon salt in cup C.
- Put one teaspoon sugar in the boiled potato cup D.
Keep these for two hours. Then, observe the four potato cups and answer the following:
- Explain why water gathers in the hollowed portion of B and C.
- Why is potato A necessary for this experiment?
- Explain why water does not gather in the hollowed-out portions of A and D.
State the difference between eukaryotes and prokaryotes
A plant cell has a cell wall made of :
Match the name of the organelle given in Column A with its function given in Column B.
| Column A (Organelle) | Column B (Function) | ||
| 1 | leucoplast | a | help in cell division |
| 2 | nucleus | b | transport of material |
| 3 | ribosomes | c | making food |
| 4 | mitochondria | d | digesting foreign bodies |
| 5 | endoplasmic reticulum | e | storage of starch and proteins |
| 6 | golgi bodies | f | making the cell turgid |
| 7 | chloroplast | g | making proteins |
| 8 | centrosome | h | controlling all the vital activities of a cell |
| 9 | vacuole | i | releasing energy |
| 10 | lysosomes | j | synthesis of cell wall in a plant cell |
Why was the invention of the microscope so important to the study of living beings?
Give one main function of the following:
Chloroplast
Match the items in column A with the appropriate items in column B:
| column A | column B |
| 1. Platform or workplace for the synthesis of proteins | a. Golgi complex |
| 2. A powerhouse of cells | b. Ribosomes |
| 3. Help in the formation of cell plate during cell division | c. Chloroplast |
| 4. Site for photosynthesis | d. Mitochondria |
| 5. Control tower of cell | e. Chromosomes |
| 6. A structure bearing genes | f. Nucleus |
What is a ‘cell’?
What is difference between us?
Prokaryotic cell and eukaryotic cell.
