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Biochemistry

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Carbohydrates

Question
18 out of 40
 

Major determinant factor in gluconeogenesis in liver depends on (AIIMS Nov 2011)



A Alanine

B Level of essential fatty acid in liver

C ADP

D None

Ans. C ADP

REF: Harper Illustrated Biochemistry 28Ed ch 20

a. The changes in enzyme activity in the liver that occur under various metabolic conditions are listed in Table 20–1.

b. The enzymes involved catalyze nonequilibrium (physiologically irreversible) reactions. The effects are generally reinforced because the activity of the enzymes catalyzing the reactions in the opposite direction varies reciprocally.

c. The enzymes involved in the utilization of glucose (ie, those of glycolysis and lipogenesis) become more active when there is a superfluity of glucose, and under these conditions the enzymes of gluconeogenesis have low activity.

d. Insulin, secreted in response to increased blood glucose, enhances the synthesis of the key enzymes in glycolysis. It also antagonizes the effect of the glucocorticoids and glucagon-stimulated cAMP, which induce synthesis of the key enzymes of gluconeogenesis.

Table 20–1. Regulatory and Adaptive Enzymes Associated with Carbohydrate Metabolism.

Activity in

Carbohydrate Feeding

Fasting and Diabetes

Inducer

Repressor

Activator

Inhibitor

Glycogenolysis, glycolysis, and pyruvate oxidation

Glycogen synthase

Insulin, glucose 6-phosphate

Glucagon

Hexokinase

Glucose 6-phosphate

Glucokinase

Insulin

Glucagon

Phosphofructokinase-1

Insulin

Glucagon

5'AMP, fructose 6-phosphate, fructose 2,6-bisphosphate, Pi

Citrate, ATP, glucagon

Pyruvate kinase

Insulin, fructose

Glucagon

Fructose 1,6-bisphosphate, insulin

ATP, alanine, glucagon, norepinephrine

Pyruvate dehydrogenase

CoA, NAD+, insulin, ADP, pyruvate

Acetyl CoA, NADH, ATP (fatty acids, ketone bodies)

Gluconeogenesis

Pyruvate carboxylase

Glucocorticoids, glucagon, epinephrine

Insulin

Acetyl CoA

ADP

Phosphoenolpyruvatecarboxykinase

Glucocorticoids, glucagon, epinephrine

Insulin

Glucagon?

Glucose 6-phosphatase

Glucocorticoids, glucagon, epinephrine

Insulin

Carbohydrates Flashcard List

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