Question

With respect to the next phase of starvation, which of the following is not true?

		Gluconeogenesis is stimulated
		Muscle protein breakdown is stimulated
		Phenylalanine is the main amino acid supplying fuel for gluconeogenesis in liver
		Pyruvate dehydrogenase is inhibited
		Glucose uptake by transporter GLUT4 is reduced

Answer 1

Answer is option 3.

After starvation, blood glucose level drops, and gluconeogenesis is stimulated in the liver and kidney. Gluconeogenesis increases the production of glucose and glucose is released out from the liver and kidney.

Muscle protein breakdown occurs after starvation to meet the need for muscle energy.

In gluconeogenesis, only glucogenic amino acids are converted into glucose. Phenylalanine is considered as both glucogenic and ketogenic amino acid. Phenylalanine is converted into oxaloacetate and fumarate, which are intermediates of TCA cycle. Thus, phenylalanine can't be used in gluconeogenesis because TCA cycle intermediates will enter for the synthesis of ATP.

Pyruvate dehydrogenase is required for conversion of pyruvate into acetyl Co-A, which is needed for progression of TCA cycle. This enzyme need to be inhibited because pyruvate is required for gluconeogenesis.