BIOCHEMISTRY - Textbook - Ostapchenko L. I. - 2012

Chapter 4. MOLECULAR ORGANIZATION AND BIOLOGICAL FUNCTIONS OF MEMBRANES

Cell membranes are supramolecular structures 8-10 nm thick that serve as the boundary regions of Cells and surround intracellular structures, partitioning The Cell into distinct compartments. Situated at the phase boundary, the membrane acts as a barrier separating the cell's contents from the external environment. However, such barriers are not absolute; rather, they provide selective transport of various substances and ions necessary for cellular function while expelling Metabolic waste products. The Plasma Membrane is the first to encounter exogenous substances, interacting with them, classifying them, and transforming their chemical energy into the energy of cellular excitation. Since most Enzymes are membrane-bound, all biochemical processes occur with the direct or indirect participation of membranes.

The term "membrane" has been used in literature for over 150 years. The first purely experimental studies suggesting the existence of a special Structure on the cell surface were conducted by C. Matteucci (1842), who reported on the "secondary" Muscle contraction resulting from nerve excitation in a second neuromuscular preparation by the current generated by the first muscle. In 1851, H. Mohl described plant cell plasmolysis, and in 1855, C. Nägeli observed differences in dye penetration into damaged and intact plant cells. He hypothesized that the cell surface is responsible for the cell's osmotic properties, while H. Hermann (1872) suggested that the nerve fiber in Matteucci's experiments conducts electric current like a cable (the nerve fiber being surrounded by an insulating sheath - now known as the myelin sheath). In 1877, W. Pfeffer published his work "Osmotic Investigations", in which he confidently postulated the existence of the membrane.

In the 1880s, H. de Vries also confirmed the existence of the plasma membrane based on osmotic studies. In 1890, physical chemist W. Ostwald drew attention to the possibility of potential differences arising across membranes.