The bilayer is composed of two layers of lipids arranged so that their hydrocarbon tails face one another to form an oily core held together by the hydrophobic effect , while their charged heads face the aqueous solutions on either side of the membrane.
Channel Proteins A passageway for molecules to move via diffusion. Requires no energy.
Protein molecule embedded in the cell membrane to which a ligand can attach to.
A molecule which binds to a receptor is called a " ligand ," and may be a peptide (such as a neurotransmitter ), a hormone , a pharmaceutical drug, or a toxin, and when such binding occurs, the receptor ordinarily initiates a cellular response.