Please select the best option for each part. Part A. Which is NOT true for Ca2+

Question

Please select the best option for each part.

Part A. Which is NOT true for Ca2+ uptake and extrusion necessary for muscle relaxation?
a) SERCA in the sarcolemma pumps most of the Ca2+ out of the cell
b) NCX and PMCA are more important for Ca2+ extrusion in cardiac muscle than skeletal muscle
c) ~1% of Ca2+ removal in cardiac muscle is via mitochondrial Ca2+ uptake
d) SERCA and PMCA use ATP hydrolysis to pump Ca2+ against its chemical gradient

Part B. Which is MOST true about the effects of -adrenergic receptor stimulation in cardiac myocytes?

a) activated protein kinase A phosphorylates the RyR2 to increase amount and duration of SR Ca2+ release

b) activated protein kinase A slows down SR Ca2+ uptake by phosphorylating SERCA

c) Both A and B

Part C. Which of the following is NOT used as a readout of RyR channel function?

a) Ca2+ spark frequency

b) Ca2+ volume

c) ATPase activity

d) [3H]ryanodine binding

Explanation / Answer

A) Answer is C

Mitochondria has no role in extrusion of calcium

SERCA releases most of the calcium during calcium contraction,NCX is widely distributed in sarcolemma of cardiocytes and serca and pmca both uses atp hydrolysis to pump calcium back to sarcoplasmic reticulumn against the concentration gradient.

B). Answer is C.

Proteim kinase A when activated phosphorylates Ryr2 present on sarcoplasmic reticulumn and increase the release of calcium.

Activated protein kinase also inhibit serca by phosphorylation hence calcium transport is inhibited that means calcium uptake is inhibited.

Hence answer should be C.

C) Answer is C.

RyR causes restricted rise in cytosolic calcium known as calcium spark.

Increase calcium induced calcium release and its volume,also in cardiac muscle it the primary mode of action.

Ryanodine locks RyR2 and acts as an antagonist.

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