Cell Biology: Plasma Membrane

Study Notes

The plasma membrane, also known as the cell membrane, separates the interior of the cell from the outside environment.
It is a double-membraned cell organelle, also called the phospholipid bilayer.
The plasma membrane is composed of carbohydrates, phospholipids, proteins, and conjugated molecules, and is approximately 5-8 nm in thickness.
It functions as a physical barrier between the external environment and the inner cell organelles, and is selectively permeable, allowing only certain molecules to move in and out of the cell.

Penetrate the phospholipid bilayer to remain permanently attached to the membrane.
Examples include glycoproteins, ion channels, carrier proteins, and protein pumps.

Are temporarily associated with one side of the membrane.
Can be removed by polar solvents.
Examples include receptor complexes involved in cell signaling (e.g., G proteins).

Determined by its function within the cell.
Non-polar amino acids (hydrophobic) associate with the lipid bilayer, while polar amino acids (hydrophilic) face aqueous solutions.
The inner surface of a protein channel is lined with polar amino acids to facilitate the passage of specific polar or charged molecules.

Derived from 20-carbon polyunsaturated fatty acids, typically arachidonic acid.
Include prostaglandins, leukotrienes, and thromboxanes.
Regulate many cell functions, including smooth muscle contractility, immune responses, and inflammatory functions.