(a) Why is the cell called the structural and functional unit of life?
(b) Why is the plasma membrane called a selectively permeable membrane ?
(c) Name the factor which decides the movement of water across the plasma membrane.
Answers
Explanation:
- Cell is called structural unit because body of all the organisms is made up of cells. It is functional unit of life because all the functions of body (physiological, biochemical. genetic and other functions) are carried out by cells.
Plasma membrane called a selectively permeable membrane because it regulates the movement of substances from within to outside of the cell. This means that the plasma membrane allows the entry of some substances while preventing the movement of some other substance.
Osmosis is a factor decides the movement of water across the plasma membrane.
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Answer:
(a)
- Structural Unit:
A living organism is made up of one or more cell. Therefore, Cell is structural unit of life.
- Functional Unit:
All life functions of an organism reside in its cell. Cell may also become specialized to perform specific functions like contraction in muscle or impulse transmission in nerve cell. There, cells are functional units of life.
(b)
Cell membrane is semi-permeable membrane for water. It permits the entry of gases through diffusion. Ions, sugar, amino acids, etc. pass through the plasma membrane by an active process. Plasma membrane is impermeable to certain materials. Therefore, it's selectively permeable.
(c)
Osmosis is the factor which decides the movement of water across the plasma membrane.