MICROANATOMY

Detailed explanation-1: -Passive transport requires no energy input, as compounds are able to move freely across the membrane based only on a favourable concentration gradient (Figure 1.11).

Detailed explanation-2: -Why is no energy required in passive transport? The membrane physically moves the molecules. Transport proteins move the molecules, so no energy is required.

Detailed explanation-3: -Passive diffusion, therefore, requires no energy expenditure by the cell; it is not saturable or subject to competition between molecules.