PLASMA MEMBRANE CONTROLS DIFFUSION : Lasix
Posted by Surgery on Jul 10, 2008
PLASMA MEMBRANE CONTROLS DIFFUSION OF SUBSTANCES BETWEEN EXTERNAL AND INTERNAL CELLULAR ENVIRONMENTS : Lasix
The plasma membrane plays a major role in the interaction of the cell with the surrounding environment. It controls the exchange of ions and macromolecules between the inside and outside of the cell. The plasma membrane contains proteins that act as receptors for extracellular ligands that modify cellular gene expression and physiology. Other membrane proteins are involved in the interaction with other cells within the same organ or migrating cells, especially of the immune system, which infiltrate the tissue during pathological conditions. The plasma membrane is also actively important in the secretion of proteins to the extracellular milieu as well as the internalization of extracellular molecules by a process known as endocytosis. For some cells, the process of endocytosis is extended to the internalization of whole cells (phagocytosis), which could be dead cells or pathogens. Ions and polar molecules pass through the plasma membrane via protein pores. These pores display substrate specificity and can be classified into pumps, carriers, and channels. Pumps drive molecules against a concentration gradient using sources of energy, especially hydrolysis of ATP.
Tags: Cell Structure and Function, LASIXCELLULAR MEMBRANES COMPARTMENTALIZE THE CELL:Cardura
Posted by Surgery on Jul 10, 2008
Cellular membranes create environments for the efficient performance of many biological processes. The plasma membrane is a barrier between the inside and the outside of the cell. Subcellular organelles, such as mitochondria and lysosomes, are also separated from one another by membranes. Cellular membranes are composed primarily of lipids, making these barriers basically impermeable to hydrophilic molecules and ions. (Cardura)
Cardura lipid
Specialized protein structures within the membrane allow the exchange of molecules and ions across these lipid barriers. The basic component of a cellular membrane is the lipid bilayer, which is composed of phospholipids (phosphoglycerides: Cardura ). The phosphate group of phospholipids is usually esterified by various alcohols (e.g., ethanolamine, choline, serine). These polar heads are exposed to the aqueous environment, whereas the fatty acid groups get together side by side forming the lipid bilayer. Sugar-containing lipids called sphingolipids are also present in membranes. Cholesterol is another component of cellular membranes. (Cardura)
Tags: Cardura, Cell Structure and Function
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