Membranes and Molecular Structure

Pysiology Lecture 2

Polar bonds

formed when the atoms at each end of the bond have an opposite charge (H-pos; O-neg); electrically charged

Non-polar bonds

formed when the atoms at each end of the bond have the same charge (h-pso; H-pos); electrically neutral

Ions

formed when an atom gains or loses one or more electrons and acquires a net electrical charge

gap junctions

allow for rapid, synchronized communication; ex.: heart muscle, retinal, and skin cells

lipids

(fats) are typically non-polar and have a very low solubility in water

amino acids

subunits of proteins

phospholipid bilayer

contains embedded proteins

transmembrane proteins

integral membrane proteind that span the entire membrane. many cross the lipid bilayer several times; amphipathic; may form channels which ions or water can cross the membrane, may be involved in transmission of chemical signals across the membrane

peripheral membrane proteins

bound to polar regions of the integral membrane proteins or phospholipids

chemical specificity

binding site determines the type of chemical that is bound

affinity

strength of ligand-protein binding; how likely it is that the ligand will leave the protein surface; most likely to influence the duration of ligand binding to a receptor

saturation

fraction of total binding sites that are occupied at any given time; influenced by: concentration of unbound ligand, affinity of the binding site for ligand

competition

occurs between multiple ligands for the same binding site; between one ligand for multiple binding sites

protein function

depends on ability of molecules and ions to bind to the surface of the proteins

ligand

molecule that binds to the protein

transmembrane proteins 2

can serve different functions, but often, that protein won’t perform its function unless it’s turned “on” through some mechanism (e.g., binding of another molecule to the protein); usually in plasma membranes; facilitiate cellular communication