The Structure of Biological Membrane Essay Example | Topics and Well Written Essays - 2000 words

The Structure of Biological Membrane - Essay ExampleHowever, membranes are not only supine barriers. They include a set of proteins specialized for promoting or catalyzing various cellular processes (Nelson & Cox 2004, p.369). Molecular rapture is the most important function of membranes facilitated by carrier and channel proteins (McKee 2004, p.62).General questions of transportation and channeling crosswise biologic membranes are well considered in the encompassing textbooks of Lodish (2003, p.245-300), Nelson & Cox (2004, p.369-420), Kuchel & Ralston (1997, p.171-184), McKee (2004, p.353-366), Garrett & Grisham (1999, p.259-326), etc., in special monographs, e.g. Keizer (2000) and also in a variety of articles.All cells acquire from its environs the raw materials for biosynthesis and for energy production, and also release to its milieu the byproducts of metabolism. Only some nonpolar compounds can cross the membrane unassisted. However, for polar or charged compounds or ions, a membrane protein is essential for transmembrane resettlementment.Membrane transport mechanisms are vital to living organisms. Ions and molecules constantly move across cell plasma membranes and across the membranes of organelles. This flux must be regulated to meet separately cells metabolic needs. For example, a cells plasma membrane regulates the entrance of nutrient molecules and the exit of waste products. Additionally, it regulates intracellular ion concentrations. Because lipid bilayers of membranes are generally impenetrable to ions and polar substances, specific transport components must be inserted into cellular membranes (McKee 2004, p.372). In the simplest cases a membrane protein facilitates the diffusion of a solute humble its concentration incline. However, transportation often occurs against a gradient of concentration, electrical charge, or both. In such cases, solutes must be pumped that requires energy. The necessary energy whitethorn come from ATP hydroly sis (i.e. directly), or may be supplied indirectly, e.g. in the form of movement of another solute down its electrochemical gradient with enough energy to carry another solute up its gradient (Nelson & Cox 2004, p.389 Garrett & Grisham 1999, p.296). Ions may also move across membranes via ion channels formed by proteins, or they may be carried across by ionophores, small molecules that mask the charge of the ions and allow them to diffuse through the lipid bilayer of membrane. With very some exceptions, the traffic of small molecules across the plasma membrane is mediated by proteins such as transmembrane channels, carriers, or pumps (Nelson & Cox 2004, p.391). So, ions cannot pass freely through the cells phospholipid membrane. Instead, most ions flow through special channels reinforced from multiple protein subunits. These subunits together form a pore across the membrane. Some channels are gated, fitted with proteins that meet as hinged doors, blocking the opening until