Question 1

Which kinase is responsible for phosphorylating IRS-1 in the insulin signaling pathway?

Accepted Answer

IRS-1 auto-phosphorylates itself

Question 2

If IRS-1 is overexpressed in muscle cells, what would you expect to see regarding glycogen synthesis?

Accepted Answer

Protein kinase B would be constitutively active, resulting in increased glycogen synthesis.

Question 3

In the insulin signaling pathway, which molecule directly activates glycogen synthase?

Accepted Answer

Dephosphorylated glycogen synthase

Question 4

Which of the following best describes the role of PI3 kinase in insulin signaling?

Accepted Answer

It converts PIP2 to PIP3, facilitating downstream signaling.

Question 5

A mutation that prevents IRS-1 phosphorylation would most likely result in which of the following?

Accepted Answer

Decreased activation of PI3 kinase and reduced glycogen synthesis.

Question 6

Which step in the insulin signaling pathway is directly responsible for the translocation of GLUT4 to the cell membrane?

Accepted Answer

Activation of protein kinase B (Akt)

Question 7

If a drug inhibits PI3 kinase activity, what would be the expected effect on glucose metabolism in muscle cells?

Accepted Answer

Decreased glucose uptake and reduced glycogen synthesis

Question 8

Which of the following equations best represents the conversion catalyzed by PI3 kinase in the insulin signaling pathway?

Accepted Answer

$$\mathrm{$$PIP_2$$ \rightarrow $$PIP_3$$}$$

Question 9

A patient with a genetic defect in protein kinase B (Akt) is likely to experience which metabolic consequence?

Accepted Answer

Decreased glucose uptake and impaired glycogen synthesis

Question 10

Which of the following is a direct consequence of insulin binding to its receptor on muscle cells?

Accepted Answer

Activation of IRS-1 by phosphorylation

Question 11

In the context of insulin signaling, which enzyme is responsible for inactivating glycogen synthase?

Accepted Answer

GSK-3 (glycogen synthase kinase 3)

Question 12

Which of the following would most likely occur if the insulin receptor is mutated and cannot bind insulin?

Accepted Answer

GLUT4 translocation to the membrane would be impaired.

Question 13

Which of the following best explains why increased IRS-1 expression leads to increased glycogen synthesis?

Accepted Answer

IRS-1 enhances the activation of downstream kinases, promoting glycogen synthase activity.

Question 14

Which of the following steps is NOT part of the insulin signaling pathway leading to glycogen synthesis?

Accepted Answer

Hydrolysis of ATP by hexokinase

Question 15

A researcher finds that muscle cells with defective IRS-1 have normal insulin receptor function. What is the most likely effect on glucose metabolism?

Accepted Answer

Impaired PI3 kinase activation and reduced glycogen synthesis

Question 16

Which of the following is the correct sequence of events in the insulin signaling pathway leading to increased glycogen synthesis?

Accepted Answer

Insulin binds receptor → IRS-1 phosphorylated → PI3 kinase activated → Akt activated → GLUT4 translocation → Glycogen synthase activated

Insulin Signaling and Glucose Metabolism: Key Concepts and Pathway Review

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