Question
In which one of the following, expenditure of energy is required?
Osmosis
Diffusion
Active transport
Passive transport
Solution
C.
Active transport
Active transport is the only phenomenon of transportation which uses energy in the form of ATP to pump molecules or ions against a concentration gradient (i.e., low to high concentration). This is mainly carried out by the carrier proteins in the plasma membrane.
Diffusion is the transport of solvent or solute molecules (i.e., across a membrane). Osmosis (i.e., net movement of solvent molecules across a semi-permeable membrane) and passive transport (i.e., movement of biomolecules or other substances across cell membrane) does not require the expenditure of energy for the transportation of molecules or ions.
