external side of plasma membrane

Definition

Target type: cellularcomponent

The leaflet of the plasma membrane that faces away from the cytoplasm and any proteins embedded or anchored in it or attached to its surface. [GOC:dos, GOC:tb]

The external side of the plasma membrane, also known as the extracellular side, is the outermost layer of the cell and is directly exposed to the external environment. It plays a crucial role in cellular communication, transport, and protection. Key features include:

- **Glycocalyx:** A carbohydrate-rich layer composed of glycoproteins and glycolipids that protrudes from the membrane surface. It acts as a protective barrier, mediates cell recognition and adhesion, and participates in signal transduction.

- **Integral membrane proteins:** These proteins are embedded within the lipid bilayer, spanning the entire membrane or partially embedded. They perform various functions, including:
- **Transporters:** Facilitate the movement of molecules across the membrane, either passively or actively.
- **Receptors:** Bind to specific ligands (e.g., hormones, neurotransmitters) triggering intracellular signaling cascades.
- **Enzymes:** Catalyze biochemical reactions occurring at the membrane surface.
- **Adhesion molecules:** Facilitate cell-cell and cell-matrix interactions.

- **Peripheral membrane proteins:** These proteins are associated with the membrane surface but are not embedded within the lipid bilayer. They can be bound to integral membrane proteins, lipids, or other membrane components. They are involved in a variety of processes, including:
- **Signal transduction:** Relaying signals from the extracellular environment to the intracellular space.
- **Structural support:** Maintaining membrane integrity and shape.

- **Lipid bilayer:** The foundation of the plasma membrane, composed of phospholipids arranged in a bilayer with hydrophilic heads facing the aqueous environment and hydrophobic tails oriented towards the interior. This structure forms a barrier that controls the passage of molecules into and out of the cell.

- **Cholesterol:** A lipid molecule embedded within the lipid bilayer that helps to maintain membrane fluidity and stability.

The external side of the plasma membrane is a dynamic and complex structure that plays a vital role in maintaining cellular function and interaction with the surrounding environment.'
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Proteins (110)

Compounds (3,397)