Question

question 20
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

a diffusion
b endocytosis
c facilitated diffusion
d sodium potassium pumps

Explanation:

Movement from higher to lower concentration without energy or membrane proteins is diffusion. Facilitated diffusion needs proteins; endocytosis and sodium-potassium pumps are active transport (use energy).

Answer:

a. diffusion