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Cell- Fundamental Unit of Life : NCERT Exercise Questions


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Q.1     Make a comparison and write down ways in which plant cells are different from animal cells.
Sol.

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 and may be absent

Q.2     How is a prokaryotic cell different from a eukaryotic cell?
Sol.

Prokaryotic cell Eukaryotic cell
Size : generally small (1 – 10µ) 1µ (micron) = 10–6m Size : generally large (5– 100µ)
Nuclear region is now defined and nuclear membrane is absent Nuclear region is well defined and surrounded by  a nuclear membrane.
Single chromosome More than one chromosome
Membrane bound cell organelles absent Membrane bound cell organelles present 

Q.3     What would happen if the plasma membrane ruptures or breaks down?
Sol.     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.


Q.4     What would happen to the life of a cell if there was no Golgi apparatus?
Sol.     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.


Q.5     Which organelle is known as the powerhouse of the cell? Why?
Sol.     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.


Q.6     Where do the lipids and proteins constituting the cell membrane get synthesised?
Sol.      Lipids are synthesized in the endoplasmic reticulum. Protein is synthesized in ribosomes which are usually present on the rough ER.


Q.7     How does an Amoeba obtain its food?
Sol.     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.


Q.8     What is osmosis?
Sol.      The movement of water from high concentration to low concentration through a semi-permeable membrane is called osmosis.



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