Which of the following is a function of a plasma membrane protein?

Which of the following is a function of a plasma membrane protein?

Plasma membranes play a crucial role in cellular communication and signaling, facilitating the transport of molecules across the cell’s boundary. Plasma membrane proteins, also known as integral or peripheral membrane proteins, serve various functions including:

  1. Transporters: These proteins facilitate the movement of substances such as ions, glucose, and amino acids into or out of cells. For example, sodium-potassium pumps (Na+/K+-ATPase) maintain ion gradients necessary for cellular processes like muscle contraction and nerve impulse transmission.

  2. Receptors: Integral membrane proteins form channels through which specific molecules can enter or exit the cell. Receptor proteins on the surface of immune cells recognize antigens from pathogens, initiating an immune response.

  3. Signal Transduction: Membrane proteins act as molecular messengers that transmit signals within the cell. G-protein coupled receptors (GPCRs), for instance, receive external stimuli and activate intracellular pathways to regulate gene expression and other cellular activities.

  4. Structural Proteins: Some membrane proteins contribute to the structural integrity of the plasma membrane itself. For example, integrin proteins help anchor the extracellular matrix to the underlying cytoskeleton.

  5. Enzymes: Integral membrane enzymes catalyze reactions that occur at the cell surface. Phospholipases Cβ (PLCβ) are examples of enzymes that break down phosphatidylinositol lipids, releasing second messengers like diacylglycerol and inositol triphosphate.

  6. Regulators: Some membrane proteins modulate the activity of other proteins or genes. Calmodulin-binding proteins (CBPs) bind calcium ions and trigger changes in the conformation of target proteins, influencing cellular responses.

  7. Adhesion Molecules: Integrins are adhesion molecules that mediate cell-cell interactions during tissue development and wound healing. They allow cells to adhere to one another and provide a scaffold for the formation of tissues.

These diverse functions highlight the versatility and importance of plasma membrane proteins in maintaining homeostasis and responding to environmental cues throughout the body.