Question

The phenomena of uptake of water at the expanse of energy by the cell and usually against the osmotic gradient is known as
A) Active absorption
B) Passive absorption
C) Osmosis
D) Diffusion

Answer 1

Generally the uptake of water against the concentration gradient requires ATP (Adenosine triphosphate) and this type of transport is carried out by the specific membrane protein present.

Complete answer: A) Active absorption occurs when transport is happening against the concentration gradient and this occurs with the help of pumps present across the membrane. Pumps are nothing but a special type of protein that carries the water molecule from low to high concentration, this movement of water is also called uphill movement.
B) Passive absorption: In this type of absorption movement of water takes place across the concentration gradient that means from higher concentration to lower concentration. This process occurs without the expenditure of energy (ATP).
C) Osmosis: It is the diffusion of water across the selectively permeable membrane. It is a passive process that means it occurs across the concentration gradient.
D) Diffusion: It is also the passive movement of water across the concentration gradient that is from higher to lower concentration without the expenditure of ATP. It is a very slow process and it is mainly for the transport of molecules up to a short distance. It is very important to plant because diffusion only processes through gaseous exchange takes place.
So, the correct answer is option (B).
Additional information: Depending upon permeability membrane are of 4 types:

1. Impermeable membrane: It does not permit the entry of any molecule. Example: Cuticle layer of leaves.
2. Semi-permeable membrane: these types of membranes allow the entry of the solvent molecule but resist the solute molecule. Example: Cellophane
3. Selectively permeable membrane: Through this type of membrane only selective solute particle can pass, Example: Plasma membrane
4. permeable membrane: this type of membrane allows the entry of all types of solute and solvent molecules. Example: cell wall

Note: Reverse osmosis: Generally osmosis occurs from high to low concentration through the selectively permeable membrane but when an external force is applied to reverse the phenomena. That is the flow of water starts to occur from low to high concentration then it is called reverse osmosis. It is mainly used in the filtration of impure water.