apical plasma membrane

Definition

Target type: cellularcomponent

The region of the plasma membrane located at the apical end of the cell. [GOC:curators]

The apical plasma membrane is a specialized region of the plasma membrane that forms the outer boundary of cells at the apical surface. This surface is typically the one facing the lumen of an organ or cavity, or the external environment. The apical plasma membrane plays a crucial role in various cellular processes, including:

* **Selective transport:** It acts as a barrier, controlling the passage of molecules into and out of the cell. This is achieved through the presence of specific transport proteins embedded within the membrane, allowing for the uptake of nutrients, the excretion of waste products, and the regulation of ion gradients.
* **Cell-cell interactions:** It can form tight junctions with adjacent cells, creating a barrier that prevents the leakage of fluids and solutes between cells. This is essential for maintaining the integrity of epithelial tissues and for controlling the movement of substances across epithelial barriers.
* **Cell signaling:** It contains receptors for signaling molecules, allowing cells to respond to environmental cues and to communicate with other cells. This is crucial for regulating cell growth, differentiation, and function.
* **Enzymatic activity:** It can harbor enzymes involved in various processes, including digestion, signal transduction, and cell adhesion.

The apical plasma membrane is often characterized by the presence of specific structures, such as microvilli, cilia, and glycocalyx. These structures enhance the surface area of the cell and play important roles in various functions, including absorption, secretion, and sensory perception.

**Microvilli** are finger-like projections that increase the surface area for absorption and secretion. They are particularly abundant in cells involved in nutrient absorption, such as intestinal epithelial cells.
**Cilia** are hair-like projections that beat rhythmically to move fluids or particles. They are found in cells involved in transport, such as those lining the respiratory tract.
**Glycocalyx** is a layer of carbohydrates that covers the external surface of the cell. It helps protect the cell, mediate cell-cell interactions, and facilitate nutrient uptake.

In summary, the apical plasma membrane is a highly specialized and dynamic structure that plays a crucial role in the function and integrity of cells, particularly those forming epithelial tissues. Its unique composition and structure allow it to perform a wide range of functions, contributing to the overall health and well-being of the organism.'
"

Proteins (155)

Compounds (3,743)