ABSTRACT
Cells are surrounded by phospholipid bilayer membranes that define their boundaries and mediate complex interactions with their environments. These membranes contain proteins and other molecular components that perform structural, enzymatic, transport, and receptor functions and that interact with the lipid matrix in a variety of ways. For example, the transport of lipid-insoluble substances such as ions across the membrane is mediated by specific carrier and channel molecules residing at least partially in the phospholipid matrix. In addition, stimulation of some neurotransmitter receptors leads to breakdown of membrane phospholipids into second messenger molecules (discussed in greater detail in Chap. 10).
