Caffeine prolongs and intensifies the effects of epinephrine. Which of the following potential mechanisms of action of caffeine
is consistent with this effect? a. inhibits cAMP phosphodiesterase, the enzyme that converts cAMP to AMP.
b. a competitive antagonist of cAMP binding to PKA.
c. stimulates phospholipase Cb.
d. inhibits sarcoplasmic/endoplasmic reticulum Ca 2 + - ATPase.
e. activates PKC.
a. inhibits cAMP phosphodiesterase, the enzyme that converts cAMP to AMP.
Explanation:
The phosphodiesterases are a group of enzymes that are capable of breaking phosphodiester bonds such as those between nucleotides in nucleic acids. The Cyclic adenosine monophosphate (cAMP) is a second messenger involved in intracellular signaling pathways. This molecule (cAMP) is hydrolyzed by the cAMP-dependent phosphodiesterase, which catalyzes the enzymatic breakdown of phosphodiester bonds (i.e., hydrolyzing cAMP to 5-AMP). The cAMP levels are modulated by the balance between its generation and the degradation via cyclic nucleotide phosphodiesterase.
Polygenic inheritance is a phenomenon that explains how a character like skin color show a range of more or less continuous variation due to many genes controlling it. And this is unlike Mendel traits that are controlled by single genes.
So, skin color in an individual is expressed as red hair and pale skin.
