Question

Insulin normally does all of the following except A. recruit glucose transporters 4 (GLUT4) from intracellular sites to the plasma membrane. B. activates protein kinase \(A\) and \(A M P\) -dependent protein kinase \((\mathrm{AMPK})\) C. activates phosphoprotcin phosphatases. D. signals an increase in sterol-response-element-binding proteins \((S R E B P-1)\) E. inhibits ketogenesis at levels lower than required to inhibit gluconeogenesis.

Short answer

A. Recruit glucose transporters 4 (GLUT4) from intracellular sites to the plasma membrane B. Activates protein kinase A and AMP-dependent protein kinase (AMPK) C. Activates phosphoprotein phosphatases D. Signals an increase in sterol-response-element-binding proteins (SREBP-1) E. Inhibits ketogenesis at levels lower than required to inhibit gluconeogenesis Answer: B. Activates protein kinase A and AMP-dependent protein kinase (AMPK)

Step-by-step solution

Understand Insulin Functions

To solve the problem, we first need to have an understanding of what insulin does in our body. Insulin is a hormone released by the pancreas that helps regulate the amount of glucose (sugar) in the blood. It does this by promoting the uptake, storage, and use of glucose in the cells and inhibiting the release of glucose from the liver.

Analyze Each Statement

Now, let's analyze each statement provided in the exercise: A. Recruit glucose transporters 4 (GLUT4) from intracellular sites to the plasma membrane: This statement is TRUE because insulin promotes the translocation of GLUT4 to the plasma membrane, which increases glucose uptake in muscle and fat cells. B. Activates protein kinase A and AMP-dependent protein kinase (AMPK): This statement is FALSE because insulin activates a different protein kinase, known as protein kinase B (AKT), rather than activating protein kinase A and AMPK. AMPK is primarily activated under conditions of low energy such as exercise and starvation, while insulin is released in response to high glucose levels. C. Activates phosphoprotein phosphatases: This statement is TRUE because insulin activates the enzyme phosphoprotein phosphatase, which dephosphorylates and activates various enzymes involved in glucose metabolism. D. Signals an increase in sterol-response-element-binding proteins (SREBP-1): This statement is TRUE because insulin promotes the synthesis of lipids (fats) by activating the transcription factor SREBP-1, which regulates the expression of genes involved in lipid synthesis. E. Inhibits ketogenesis at levels lower than required to inhibit gluconeogenesis: This statement is TRUE because insulin inhibits ketogenesis (formation of ketone bodies) at lower levels than needed to inhibit gluconeogenesis (production of glucose from non-carbohydrate sources). This helps to prevent excessive ketone body production and maintain blood glucose levels.

Identify the Incorrect Statement

According to the analysis in Step 2, the incorrect statement regarding the functions of insulin is: B. Activates protein kinase A and AMP-dependent protein kinase (AMPK) Insulin does not activate protein kinase A and AMPK; instead, it activates protein kinase B (AKT). Therefore, the correct answer to this exercise is option B.