Chapter 11: Membrane Structure

plasma membrane

The protein-containing lipid bilayer that surrounds a living cell

lipid bilayer

thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for all cell membranes.

phospholipids

The major type of lipid molecule in cell membranes. Generally composed of two fatty acid tails linked to one of a variety of phosphate-containing polar groups.

phosphatidylcholine

Common phospholipid present in abundance in most cell membranes; uses choline attached to a phosphate as its head group.

amphipathic

Having both hydrophobic and hydrophilic regions, as in a phospholipid or a detergent molecule.

fat droplets

Large cluster of hydrophobic fats or oils that forms inside the cells.

unsaturated

Describes an organic molecule that contains one or more double or triple bonds between its carbon atoms.

saturated

Describes an organic molecule that contains a full complement of hydrogen; in other words, no double or triple carbon–carbon bonds.

cholesterol

Short, rigid lipid molecule present in large amounts in the plasma membranes of animal cells, where it makes the lipid bilayer less flexible.

scramblase

a protein that facilitates the rapid, bidirectional, and non-specific movement of phospholipids between the two leaflets of a cell membrane, disrupting the normal lipid asymmetry

flippase

transmembrane lipid transporter proteins located in the cell membrane. They are responsible for aiding the movement of phospholipid molecules between the two layers, or leaflets, that compose the membrane

membrane proteins

a protein associated with the lipid bilayer of a cell membrane

glycocalyx

Protective layer of carbohydrates on the outside surface of the plasma membrane formed by the sugar residues of membrane glycoproteins, proteoglycans, and glycolipids.