Question

In the light of carrier concept, the transport of ion across the membrane against concentration gradient is
A. Passive process
B. Non-osmotic process
C. Osmotic process
D. Active process

Answer 1

Hint: Consistent with carrier concept for transport of ion in plants, transport is mediated by specific carriers. The ion carrier is activated in presence of ATP and a kina’s enzyme when the ion is transported against the concentration gradient. Since the transport occurs against the concentration gradient and consumes energy of ATP, it's a lively transport mechanism.

Complete answer:
> Option A is wrong.
The movement of ions and other atomic molecular substances across cell membranes is called the transportation without need of energy input. The main four types of transport are simple diffusion, facilitated diffusion, filtration and the osmosis.

> Option B is wrong.
The active non-osmotic theory was given by Thiemann and Kramer. Consistent with this theory, sometimes water is absorbed against the concentration gradient and requires much energy released from respiration of the root.

> Option C is wrong.
It drives a net current across the membrane, tending to make an electrical potential, with the cells inside negative relative to the surface. Because the cell wall is weakly permeable to water, water moves slowly into or out of cells down its concentration gradient, a process called osmosis.

> Option D is correct.
The ion carrier is activated in presence of ATP and a kina’s enzyme when the ion is transported against the concentration gradient. The activated carrier forms a posh with an ion at the outer surface and transported in. Because this process involves ATP, hence, it's called active process.

Hence, the correct answer is option (D).

Note: When the ion is transported against the concentration gradient the ion carrier is activated in presence of ATP and a kinase enzyme. The activated carrier forms a posh with an ion at the outer surface and transported in, because this process involves ATP, hence, it's called active process.