Friday, 17 May 2013

Composition and Functions of Cell membranes

The Plasma membranes are made of lipids, proteins and carbohydrates

Lipids
Barrier separating the interior of the cell from its environment. Also act as a barrier between the solutions inside the cell separating contents of an organelle from the cell cytoplasm. For example: nucleus is surrounded by two layers of membranes that are actually extensions of the membrane surrounding the cell.  These nuclear membranes keep the DNA inside of the nucleus

Lipid molecules are called PHOSOPHOLIPIDS that made of fatty acids, glycerol, phosphate and hydrophilic organic derivative. Amphipathic one end of molecule is hydrophobic and the other side is hydrophillic) Fluid with the degree of un saturation of fatty acids determining the fluidity Barrier to polar molecules Basis for the cell signaling system

Proteins
The proteins within the plasma membrane are the functional part of the membrane allowing for transport of materials through the membrane AND sending and receiving signals to and from other cells

Basically these proteins can act as, pumps, gates, receptors, energy transducers and enzymes OR receptors for the endocytosis of material and cell cell signaling. The proteins associated with the outside surface of the lipid by layer are called EXTRINSIC PROTEINS. These can be easily removed

The proteins that are embedded in the membrane are called INTRINSIC PROTEINS. They can only remove with detergents that disrupt the cell membrane. Integral proteins also have a hydrophobic portion that spans the hydrophobic interior of the lipid bi layer. Some of these inner proteins also have INTEGRINS their job is to connect the outside proteins to the cytoskeleton inside the cell

Carbohydrates
Modify the lipid and protein molecules

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