Question

a substance moves across a cell membrane from a higher concentration to a lower concentration, without using the cells energy or the use of membrane proteins, this is due to _________.

o a endocytosis
o b sodium potassium pumps
o c facilitated diffusion
o d diffusion

Explanation:

The movement of a substance from higher to lower concentration without energy or membrane proteins is passive transport. Diffusion fits this as it requires no energy, no proteins, and moves down the concentration gradient. Endocytosis (a) and sodium potassium pumps (b) are active (use energy). Facilitated diffusion (c) uses proteins.

Answer:

d. diffusion