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Biochemistry

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Carbohydrates

Question
35 out of 40
 

Phosphorylase B in the muscle is normally kept in inhibited state by which one of the following? (AIPG 2008)



A ATP
B AMP

C Ca2+
D Glucose

Ans. B AMP

a. Muscle Phosphorylase: This exists in an active ‘a ’form and an inactive ‘b ’form. Phosphorylase (MW –194,800)is a dimmer containing two identical subunits and occurs tightly bound to glycogen granules; a ’is the phosphorylated form and ‘b ’the dephosphorylated form.

b. Phosphorylation requires ATP and occurs at the –OH groups of serine in each subunit of the ‘b ’form to produce the ‘a ’form. This phosphorylation is brought about by the enzyme phosphorylase kinase.

c. In presence of AMP, the muscle phosphorylase remains in inactive form.

d. Presence of Ca 2+ leads to activation of phosphorylase kinase which leads to subsequent activation of muscle glycogen phosphorylase.

Carbohydrates Flashcard List

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