Membrane Proteins Functions Flashcards
- A protein (left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute.
- Some transport proteins (right) hydrolyze ATP as an energy source to actively pump substances across the membrane.
Transport
*A membrane protein exposed to the outside of the cell may have a binding site that fits the shape of a specific chemical messenger, such as a hormone.
*When bound, the chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell.
Receptors for signal transduction
*A membrane protein may be an enzyme with its active site exposed to substances in the adjacent solution.
*A team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway as indicated (left to right) here.
Enzymatic activity
Some glycoproteins (proteins bonded to short chains of sugars which help to make up the glycocalyx) serve as identification tags that are specifically recognized by other cells.
Cell-cell recognition
Elements of the cytoskeleton (cell’s internal framework) and the extracellular matrix (fibers and other substances outside the cell) may anchor to membrane proteins.
* Helps maintain cell shape, fixes the location of certain membrane proteins, and plays a role in cell movement.
Attachment to the cytoskeleton and extracellular matrix (ECM)
Membrane proteins of adjacent cells may be hooked together in various kinds of intercellular junctions.
* Some membrane proteins (cell adhesion molecules or CAMs) of this group provide temporary binding sites that guide cell migration and other cell-to-cell interactions.
Cell-to-cell joining