Question

Signal transduction pathways are involved in regulating carbohydrate metabolism. Which of the following statements is false?

Group of answer choices

When blood sugar is high, insulin signaling inhibits gluconeogenesis and activates glycolysis by decreasing fructose-2,6-bisphosphate synthesis.

Epinephrine binding to its receptor results in phosphorylation and inactivation of glycogen synthase.

Glucagon stimulates an increase in blood glucose levels by activating glycogen breakdown and stimulating gluconeogenesis.

Insulin signaling results in the activation of phosphatases, which remove phosphate from glycogen phosphorylase and reduces glycogen breakdown.

Glucagon signaling stimulates the formation of cAMP whereas insulin signaling reduces cAMP levels.

Answer 1

Statement 1, incorrect. Presence of high glucose inhibis gluconeogenesis but it does not decrease fructose 2,6 bisphospahte synthesis. Fructose 2,6-bisphosphate is the most critical regulator for the activity of Phospho fructo kinase PFK-1. Fructose 2,6-bisphosphate is far more powerful than AMP & ATP. When [fructose 2,6-bisphosphate] concentration goes down, glycolysis is inhibited, and glucose enters into the blood. See figure 1

Statement 2: Correct Binding of epinephrine lead to phosphorylation cascade.

Statement 3 : correct

Glucagon is a hormone released by pancreas. It is a catabolic hormone meaning it breaks glycogen in liver cells through cascade reactions to produce glucose-1-phosphate, so that glucose level increases

Gluconeogenesis is synthesis of glucose from non carbohydrate precursors in situation when desired amount of blood glucose is not present for normal functioing of central nervous system.

Statement 4: Incorrect

Phosphorylation is enhanced after insulin comes into action

Phosphorylation of glycogen synthase by GSK3 inhibits glycogen synthesis; therefore the inactivation of GSK3 by AKT promotes glucose storage as glycogen

Statement 5 : Incorrect partially

INSULIN signalling does not involve cAMP.