Question

All of the following statements are true EXCEPT:

a. Action potentials open voltage-sensitive calcium channels in the sarcoplasmic reticulum
b. Ca2+ is sequestered in the sarcoplasmic reticulum
c. Binding of Ca2+ to troponin C causes a conformational change, shifting the tropomyosin and exposing the mysoin binding site
d. Action potentials are carried into the cell interior by transverse (T) tubules
e. In the relaxed state, cytoplasmic Ca2+ levels are high—low

Answer 1

Action potentials are carried into the cell interior by transverse (T) tubules and not voltage-sensitive calcium channels in the sarcoplasmic reticulum. In the relaxed state, cytoplasmic Ca2+ levels are low, not high. Ca2+ is sequestered in the sarcoplasmic reticulum, and its binding to troponin C causes a conformational change that exposes the myosin binding site and initiates muscle contraction.

Step-by-step explanation:

Action potentials are carried into the cell interior by transverse (T) tubules, not voltage-sensitive calcium channels in the sarcoplasmic reticulum.

In the relaxed state, cytoplasmic Ca2+ levels are low — not high.

Ca2+ is sequestered in the sarcoplasmic reticulum, and the binding of Ca2+ to troponin C causes a conformational change, shifting the tropomyosin and exposing the myosin binding site, which initiates muscle contraction.