Most important factor in transport across a membrane? Concentration gradient

Most important factor in transport across
a membrane?
a) Charge of particle
b) Membrane thickness
c) Size of particle
d) Concentration gradient
Correct Answer - D
Ans. D. Concentration gradient
[Ref Guyton 12h/e p. 48-501]
Transport across a cell membrane is divided into passive or active,
based on whether it is along the concentration gradient or against
the concentration gradient.

  1. Passive transport
    It is in the direction of concentration gradient i.e., “Downhill
    movement".
  2. Active transport
    It is against the direction of concentration gradient, i.e., “Uphill
    movement”