Explain the function of peripheral proteins in the cell membrane.

Peripheral proteins function as enzymes, transporters, or receptors in the cell membrane, facilitating various cellular processes.

Peripheral proteins are a type of protein that are attached to the surface of the cell membrane. Unlike integral proteins, which are embedded within the lipid bilayer, peripheral proteins are not inserted into the hydrophobic core of the membrane. Instead, they are loosely bound to the lipid bilayer, often attached to integral proteins. This allows them to be easily removed without disrupting the structure of the membrane.

These proteins play a crucial role in various cellular processes. They can function as enzymes, catalysing specific reactions at the membrane surface. For instance, some peripheral proteins on the inner surface of the cell membrane catalyse the transfer of phosphate groups to other proteins, a process known as phosphorylation. This is a key mechanism by which cells regulate protein function and transmit signals.

Peripheral proteins can also act as transporters, helping to move substances across the cell membrane. While integral proteins often facilitate the transport of larger or charged molecules, peripheral proteins can assist in the transport of smaller, uncharged molecules. They can also help to anchor the cytoskeleton to the plasma membrane, providing structural support to the cell.

Furthermore, peripheral proteins can serve as receptors, binding to specific molecules and triggering a response within the cell. For example, some peripheral proteins on the outer surface of the cell membrane can bind to hormones or other signalling molecules. This binding can trigger a cascade of events within the cell, leading to changes in cell function or behaviour.

In summary, peripheral proteins are vital components of the cell membrane, contributing to its functionality and versatility. They facilitate a range of cellular processes, from enzymatic reactions and substance transport to signal transduction, making them indispensable for the proper functioning of the cell.