1. The basic structural unit of a biomembrane is the phospholipid bilayer. Acetic acid and ethanol are each composed of two carbons, hydrogen and oxygen, and both enter cells by passive diffusion. At pH 7' one is much more membrane permeable than the other' Which is more permeable and why? Predict how the permeability of each is altered when the pH is reduced to 1.0, a value typical of the stomach.