Question

Which of these enzymes can be considered as “the Master controller of metabolic processes” because of regulatory effects on metabolic processes?

	A.	Hexokinase
	B.	Protein kinase A
	C.	Pyruvate Dehydrogenase complex (PDH)
	D.	Hormone sensitive lipase
	E.	DNA polymerase

Which of the following statements concerning synthesis of ATP by oxidative phosphorylation in animals is NOT Correct?

.	It depends on an electrochemical gradient generated when protons are pumped in to the intermembrane space
	B.	It requires ADP which is brought in exchange of ATP
	C.	FADH2 results in generation of more ATPs as compared to NADH
	D.	All of the above

The following are involved in regulation of the urea cycle EXCEPT,

	A.	Arginine
	B.	N-acetylglutamate
	C.	High dietary protein
	D.	Fumarate

Answer 1

Question 1

The correct answer is option C - Pyruvate Dehydrogenase complex (PDH)

Explanation: This enzyme converts pyruvate to Acetyl CoA, NADH+H⁺. All the Acetyl Co-A then enters TCA cycle. All the metabolic processes involves TCA cycle as proteins and fatty acids ultimately metabolized by TCA cycle. As Acetyl Co-A is one of the starting substrate of TCA cycle, its production is very much important in controlling the cycle and thereby whole metabolism in the cell. So correct answer is Pyruvate Dehydrogenase complex (PDH).

Question 2

The correct answer is option D- all of the above

Explanation: FADH2 generates 1.5 molecules of ATP whereas NADH provides 2.5 molecules of ATP when oxidized completely by oxidative phosphorylation n mitochondria. Protons are pumped outside and thus electrochemical gradient is established, not inside. They are brought back to matrix by ATP synthase enzyme and then ATP is formed.

Question 3 The correct answer is option

Explanation: Fumarate is formed by the action of the enzyme arginosuccinate lyase which converts arginosuccinate into arginine and fumarate. Fumarate is directly not involved in Urea cycle regulation, it is a by product which links Urea cycle with TCA cycle. So it has no role in regulation of Urea cycle.