CHAPTER NO 5
FUNDAMENTAL UNIT OF LIFE
DATE -18 APRIL 2016
Q - Why does the water come out from the cucumber when we add salt to it?
A - The cells of the cucumber have low salt content while the water around it has high salt content. The water comes out of the cucumber to balance the amount of water in the two mediums.
Question -1. Make a comparison and write down ways in which plant cells are different from animal cells.
DATE - 07 MAY 2016
Question -1. Make a comparison and write down ways in which plant cells are different from animal cells.
Answer:
| Plant cell | Animal cell |
|---|---|
| Cell wall present | Cell wall absent |
| Plastids present | Plastids absent |
| Vacuole is usually very large and single | Vacuoles are much smaller an may be absent |
Question -2. How is a prokaryotic cell different from a eukaryotic cell?
Answer:
| Prokaryotic cell | Eukarytotic cell |
|---|---|
| Size: generally small (1 - 10 μ) 1 μ (micron) = 10 - 6 m | Size: generally large (5 - 100 μ) |
| Nuclear region is now defined and nuclear membrane is absent | Nuclear region is well defined and surrounded by a neclear membrane |
| Single chromosome | More than one chromosome |
| Membrane bound cell organelles absent | Membrane bound cell organelles present |
Question -3. What would happen if the plasma membrane ruptures or breaks down?
Answer: Plasma membrane provides a container for the cell organelles and cytoplasm. Moreover, plasma membrane also protects the contents of a cell from external environment. In case the plasma membrane ruptures or breaks down, the cell contents would be exposed to the external environment. This would prove lethal for the cell and the cell would cease to exist.
Question - 4. What would happen to the life of a cell if there was no Golgi apparatus?
Answer: Golgi apparatus plays the important role of packaging various substances for further use or for storage. If there was no Golgi apparatus, various substances would not be in a position to be transformed in proper forms for further use. Certain substances; like protein and lipid are important for the formation of plasma membrane and hence absence of Golgi apparatus will hamper the formation of new cells during cell division.
Question -5. Which organelle is known as the powerhouse of the cell? Why?
Answer: Mitochondrion is known as the powerhouse of the cell. The reason for this is the fact that cellular respiration takes place in mitochondria and the energy released after that gets stored in mitochondria; in the form of ATP. These ATP molecules are utilized on an SOS basis.
Question - 6. Where do the lipids and proteins constituting the cell membrane get synthesised?
Answer: Lipids are synthesized in the endoplasmic reticulum. Protein is synthesized in ribosomes which are usually present on the rough ER.
Question - 7. How does an Amoeba obtain its food?
Answer: Amoeba obtains its food through a process called phagocytosis. The cell membrane of amoeba is projected into numerous finger-like outgrowths; called pseudopodia. Amoeba surrounds a food particle by pseudopodia and makes a food vacuole; after engulfing the food.
Question - 8. What is osmosis?
Answer: The movement of water from high concentration to low concentration through a semi-permeable membrane is called osmosis.
