BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 4. MOLECULAR ORGANIZATION AND BIOLOGICAL FUNCTIONS OF MEMBRANES

4.3. Membrane Functions

Membranes are responsible for performing numerous vital cellular Functions. It is hard to name a single biochemical process that occurs without the direct or indirect participation of membranes. Therefore, it is no exaggeration to state that membranes act as the regulators of cellular METABOLISM.

Cellular membranes maintain the intracellular composition, selectively accumulate necessary compounds, and actively excrete Metabolic waste products. Within cellular Organelles, membranes help maintain conditions distinct from those in other PARTS OF THE Cell. This compartmentalization ensures that a multitude of processes can occur simultaneously within extremely limited volumes and under diverse conditions. It also enables The Cell to store BIOLOGICALLY ACTIVE SUBSTANCES in isolated compartments until they are required for specific functions (such as lysosomal Enzymes, Hormones, and Neurotransmitters). The regulatory function of membranes can be summarized as follows: they serve as a barrier, a defense against external threats, an intercellular telegraph, an energy station, and more. Nevertheless, among all Membrane Functions, three primary ones stand out:

✵ the barrier function ensures the selective, regulated, passive, and active exchange of substances between the cell and its environment.

✵ the matrix function provides the spatial arrangement and orientation of Membrane Proteins, ensuring their optimal interaction.

✵ the mechanical function maintains the integrity and autonomy of intracellular structures.

Other important membrane functions include the energy function (ATP synthesis), Generation and Conduction of biopotentials, receptor functions (mechanical, acoustic, olfactory, visual, chemical, and thermoregulatory), enzymatic activity (ATPases, protein Kinases), and many others. Membranes perform these functions thanks to both their unique MOLECULAR Organization AND their immense surface area—which reaches tens of thousands of square meters in The Human Body.