Plasma Membrane Lipid Molecules

Plasma membrane lipid molecules

A) allow ions to diffuse across the membrane against their concentration gradient.
B) are entirely hydrophobic.
C) allow ions to diffuse across the membrane down their concentration gradient.
D) are arranged with their polar, hydrophilic heads facing outward and their hydrophobic tails extending to the middle of the layer.
E) are arranged with their polar, hydrophilic heads facing inward to the middle of the layer and their hydrophobic tails extending outward.