Cell Membrane Components and Their Functions

Phospholipid Bilayer

Composed of two layers of phospholipids. Hydrophobic tails face inward, hydrophilic heads face outward. Acts as a barrier, separating the internal environment of the cell from the external environment. Facilitates a controlled internal environment, maintaining homeostasis. Supports the embedding of other proteins and molecules, contributing to the membrane's functionality.

Glycoprotein

A protein with a carbohydrate chain attached to its surface. Extends into the external environment, facilitating interaction between the cell and its surroundings. Crucial for cell recognition processes, aiding in cell communication and response to external signals.

Glycolipid

A lipid molecule that has a carbohydrate chain attached to its surface. Introduces communication capabilities between cells through carbohydrate extension into the external environment. Plays a role in stabilizing the cell membrane structure.

Cholesterol

A type of steroid characterized by a core structure made up of four interconnected carbon rings. A small molecule interspersed among phospholipids in the bilayer. Regulates membrane fluidity: At low temperatures, prevents tight packing of phospholipids. At high temperatures, maintains structural integrity by helping to hold the membrane together.

Channel Protein

A transmembrane protein that traverses the membrane with a central channel. Facilitates the transport of molecules and ions across the cell membrane. Permits passage of large or small polar molecules that cannot diffuse freely across the bilayer on their own.

Carrier Protein

A transmembrane protein with a specific binding site for target molecules. Also assists in the transport of large polar molecules and ions. More selective in the molecules it carries compared to channel proteins, facilitating specialized transport.

Receptor Protein

A transmembrane protein that may span the membrane multiple times, featuring a domain extending into the external environment. Acts in cell signaling: When a signaling molecule, such as a hormone, binds to it, the receptor changes shape. This conformational change triggers an internal cellular response, influencing various physiological activities.