Hw #9 Flashcards
How does the composition of the bilayer affect it’s properties?
The presence of the unsaturated fatty acids in membrane components leads to a greater fluidity than with a preponderance of saturated fatty acids. Conversely the presence of saturated fatty acids and cholesterol tends to stiffen the bilayer. The packing of molecules in the bilayer can undergo a reversible transition form order to disorder. Lateral motion of lipid molecules within one layer of a membrane occurs frequently.
What is the structure of lipid bilayers?
A biological membrane consist of a lipid part and a protein part. The lipid part is a bilayer, with the polar head groups in contact with the aqueous interior and exterior of the cell, and the nonpolar portions of the lipid in the interior of the membrane.
How are proteins associated with the bilayer in membranes?
The proteins that occur in membranes can be peripheral proteins, which are found on the surface of the membrane, or integral proteins, which lie within the lipid bilayer. Various structural motifs such as bundles of seven alpha helices occur in proteins that span membranes. Peripheral proteins are loosely attached to one surface of the membrane by hydrogen bonds or electrostatic attractions, whereas integral proteins are embedded solidly in the membrane.
What do prostaglandins and leukotrienes have to do with lipids?
The unsaturated fatty acid arachidonic acid is the precursor of prostaglandins and leukotrienes, compounds that have a wide range of physiological activities. Stimulation of smooth muscle contraction and induction of inflammation are common to both classes of compounds. Prostaglandins are also involved in control of blood pressure and inhibition of blood platelet aggregation.
How do proteins an the lipid bilayer interact with each other in membranes?
The fluid mosaic model describes the interaction of lipids and proteins in biological membranes. The proteins float in the lipid bilayer.
