#Question id: 15763
#Unit 5. Developmental Biology
#Question id: 2589
#Unit 2. Cellular Organization
Following statements are regarding to the mechanism of thick filament regulation.
A. In vertebrate smooth muscle, phosphorylation of the myosin regulatory light chain (LC) activates contraction.
B. At Ca2+ concentrations of more than 10−6 M, the regulatory light chain is not phosphorylated, and the myosin adopts a folded conformation.
C. When the Ca2+ level rises, Ca2+ binds calmodulin (CaM), which undergoes a conformational change (CaM*). The CaM*-Ca2+ complex binds and activates myosin light chain kinase (MLC kinase), which then phosphorylates the myosin LC. This phosphorylation event unfolds the myosin II, which is now active and can assemble into bipolar filaments to participate in contraction.
D. When the Ca2+ levels drop, the myosin LC is dephosphorylated by myosin light-chain (MLC) phosphatase, which is dependent on Ca2+ for activity, causing muscle relaxation.
Which of the following combination is correct?
#Question id: 27946
#Unit 1. Molecules and their Interaction Relevant to Biology
#Question id: 14966
#Unit 2. Cellular Organization
#Question id: 12383
#Unit 7. System Physiology – Animal