9th class bio science 2nd lesson questions and answers
Answers
Explanation:
.................... EXERCISE (page 66)
1. Make a comparison and write down ways in which plant cells are different from animal cells.
Answer
Animal cell Plant cell
Has a cell wall. Has cell wall made up of cellulose.
It does not contain chloroplast. It contains chloroplast.
It has centrosome. It does not has centrosome.
Vacuoles are smaller in size. Vacuoles are larger in size.
Lysosomes are larger in number. Lysosomes are absent or very few in number
Prominent Golgi bodies are present. Subunits of Golgi bodies are present.
2. How is a prokaryotic cell different from a eukaryotic cell?
Answer
Prokaryotic cell Eukaryotic cell
Most prokaryotes are unicellular. Most eukaryotes are multi-cellular.
Size of the cell - (0.5- 5 μ). Size of the cell - (50- 100 μ).
It contains a single chromosome. It contains more than one chromosome.
Nucleolus is absent. Nucleolus is present.
Membrane-bound cell organelles such as plastids, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. are absent. Cell organelles such as mitochondria, plastids, endoplasmic reticulum, Golgi apparatus, lysosomes, etc. are present.
Cell division occurs through binary fission Cell division occurs by mitosis.
3. What would happen if the plasma membrane ruptures or breaks down?
Answer- If ever the plasma membrane ruptures or breakdown then the cell will not be able to exchange material from its surroundings by diffusion. As a result of it the protoplasmic material will disappear and the cell will die.
4. What would happen to the life of a cell if there was no Golgi apparatus?
Answer- Golgi apparatus performs the function of a storage modification and packaging of products. If Golgi apparatus is not there then materials synthesized by cell will not be packaged and transported.
5. Which organelle is known as the powerhouse of the cell? Why?
Answer- Mitochondria are known as the powerhouse of cells because energy required for various chemical activities needed to support life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules.
6. Where do the lipids and proteins constituting the cell membrane get synthesized?
Answer- Lipids are synthesized in Smooth endoplasmic reticulum and the proteins are synthesized in endoplasmic reticulum.
7. How does an Amoeba obtain its food?
Answer- Amoeba obtains food using temporary finger-like extensions on the cell surface which fuse over the food particle forming a food-vacuole. Complex substances are broken down into simpler ones inside the food vacuole which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out resulting in excretion.
8. What is osmosis?
Answer- Osmosis is the process in which water molecules moves from the region of high concentration to a region of low concentration through a semi permeable membrane.
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