10. Cell and Cell Organelles
Complete solutions to the Exercises. Maharashtra State Board (Balbharati), Grade Eight General Science.
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Exercises
(a) I am ATP producing factory. Mitochondrion
(b) I am single layered, but maintain cellular osmotic pressure. Vacuole
(c) I support the cell, but I am not cell wall. I have a body resembling net. Endoplasmic reticulum
(d) I am chemical factory of the cell. Cytoplasm
(e) Leaves are green because of me. Chloroplast
(a) RBCs had mitochondria.
RBCs would use some of the oxygen for themselves. So less oxygen would reach the other cells of the body.
(b) There had been no difference between mitochondria and plastids.
Plastids make food and mitochondria release energy from food. If there was no difference, these two works would not be done properly. The cell would not get food or energy.
(c) Genes had been absent on the chromosomes.
Hereditary characters would not be passed from parents to offspring. The offspring would not resemble their parents.
(d) Plasma membrane had not been selectively permeable.
Harmful substances would enter the cell. Useful substances would go out. So the cell would die.
(e) Plants lacked anthocyanin.
Flowers and fruits would not have blue, violet or purple colour. Insects would not be attracted for pollination.
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(a) Nucleolus, mitochondria, plastids, endoplasmic reticulum Nucleolus
Nucleolus is present inside the nucleus. It has no membrane. The others are membrane-bound cell organelles.
(b) DNA, ribosomes, chlorophyll Chlorophyll
Chlorophyll is a pigment found only in plant cells. DNA and ribosomes are found in all cells.
Structure of a plant cell.
Structure of an animal cell.
(a) Plasma membrane
- It separates the cell contents from the outer environment.
- It allows only selected substances to enter or leave the cell.
- It maintains homeostasis.
(b) Cytoplasm
- All chemical reactions of the cell take place in it.
- Cell organelles are suspended in it.
- It stores substances like glucose, amino acids and vitamins.
(c) Lysosome
- It digests the waste material in the cell.
- It destroys bacteria and viruses.
- It destroys old organelles.
- It digests the old cell itself. So it is called a ‘suicide bag’.
(d) Vacuole
- It maintains the osmotic pressure of the cell.
- It stores food, water and waste materials.
- In plant cells, it gives turgidity to the cell.
(e) Nucleus
- It controls all the activities of the cell.
- It controls cell division.
- Its chromosomes carry genes. Genes pass hereditary characters to the next generation.
| Part | Pigment |
|---|---|
| a. Red tomato | 4. Lycopene |
| b. Green leaf | 1. Chlorophyll |
| c. Carrot | 2. Carotene |
| d. Violet | 3. Anthocyanin |