G. An explanation of the Genetic Code: DNA is a two-stranded molecule. Each strand is a polynucleotide composed of A (adenosine), T (thymidine), C (cytidine), and G (guanosine) residues polymerized by dehydration synthesis in linear chains with specific sequences.
Note: There are more than two types of epinephrine receptors on smooth muscle cells, so epinephrine may affect smooth muscle in other tissues in other ways. (There are subtypes of alpha and subtypes of beta.) * Details of how PLC generates IP3 are on handout 12A. We will go over this later.
*NOTE: The MC2-R receptor system looks and works similarly to the beta-2 adrenergic receptor system, which initiates relaxation of the bronchiole muscle cells (seen later in the movie) when epinephrine binds to it. When it binds, ACTH stimulates the receptor to change shape. This conformational change causes the G protein complex to become activated and uncoupled. When the G protein stimulates it, Adenylate cyclase converts ATP (the cell's energy molecule) into cAMP (a signaling molecule).