What Are The Major Components Of Biological Membranes And How Do They :: essays research papers fc

What Are The Major Components of Biological Membranes And How Do They ContributeTo Membrane Function?.Summary.The role of the biologic membrane has proved to be vital in countlessmechanisms necessary to a cells survival. The phospholipid bilayer performs thesimpler functions such as compartmentation, protection and osmoregulation. Theproteins perform a wider range of functions such as extracellular interactionsand metabolic processes. The carbohydrates argon build in conjunction with boththe lipids and proteins, and therefore enhance the properties of both. This mayvary from recognition to protection.Overall the biological membrane is an extensive, self-sealing, fluid,asymmetric, selectively permeable, compartmental barrier inherent for a cell ororganelles correct functioning, and thus its survival.Introduction.Biological membranes surround all living cells, and may also be foundsurrounding some of an eukaryotes organelles. The membrane is essential to thesurvival of a cell due to its diverse range of functions. There are generalfunctions common to all membranes such as control of permeability, and thenthere are specialised functions that depend upon the cell type, such asconveyance of an action potential in neurones. However, despite the innovation offunction, the structure of membranes is remarkably similar.All membranes are composed of lipid, protein and carbohydrate, but it isthe ratio of these components that varies. For example the protein component maybe as high as 80% in Erythrocytes, and as low as 18% in myelinated neurones.Alternately, the lipid component may be as high as 80% in myelinated neurones,and as low as 15% in skeletal muscle fibres.The initial model for membrane structure was proposed by Danielli andDavson in the late 1930s. They suggested that the plasma membrane consisted of alipid bilayer coated on both sides by protein. In 1960, Michael Robertsonproposed the Unit Membrane Hypothesis which suggests that all biologicalmembranes -reg ardless of location- have a similar basic structure. This has beenconfirmed by research techniques. In the 1970s, Singer and Nicholson announced amodified version of Danielli and Davsons membrane model, which they called the unruffled Mosaic Model. This suggested that the lipid bilayer supplies the backboneof the membrane, and proteins associated with the membrane are not fixed inregular positions. This model has yet to be disproved and will therefore be thebasis of this essay.The lipid component.Lipid and protein are the two predominant components of the biologicalmembrane. There are a variety of lipids found in membranes, the majority ofwhich are phospholipids. The phosphate head of a lipid molecule is hydrophilic,while the long fatty acid tails are hydrophobic. This gives the overall moleculean amphipathic nature.