Phosphorylation of phospholamban by PKA increases the activity of SERCA2a. What
ID: 181639 • Letter: P
Question
Phosphorylation of phospholamban by PKA increases the activity of SERCA2a. What is the result if heart rate stays the same and the level of phospholamban phosphorylation increases?
a) SR Ca concentration decreases, amount of SR Ca released decreases, and developed force decreases
b) SR Ca concentration decreases, amount of SR Ca released stays same, and developed force decreases
c) SR Ca concentration increases, amount of SR Ca released stays same, and developed force stays the same
d) SR Ca concentration increases, amount of SR Ca released decreases, and developed force stays the same
e) SR Ca concentration increases, amount of SR Ca released increases, and developed force increases
Explanation / Answer
c) SR Ca concentration increases, amount of SR Ca released stays same, and developed force stays the same
Phospholamban regulates the calcium pump present in cardiac muscle cells.
Phospholamban in its unphosphorylated state inhibits the cardiac muscle sarcoplasmic reticulum Ca2+ATPase (SERCA2), but will not inhibit in its phosphorylated state. SERCA main function is transferring calcium to the lumen of the sarcoplasmic reticulum from the cytosol utilizing ATP.
So, when the level of Phospholamban phosphorylation increases it will increase the SR Ca2+concentration, but in the question they have mentioned that heart rate stays same, so the amount of SR Ca2+released will stay the same and developed force stays the same.