A nurse is explaining the role of insulin in glucose metabolism to a pregnant woman who has gestational diabetes.

The nurse should tell the woman that insulin is a hormone that does which of the following?

The correct answer is

C. It transports glucose from the bloodstream into the cells for energy production.

Insulin is a hormone that regulates the metabolism of carbohydrates, fats, and proteins. It promotes the absorption of glucose from the blood into cells, where it can be used for energy or stored as glycogen or fat. It also inhibits glucose production and secretion by the liver and stimulates lipogenesis and protein synthesis. Insulin is essential for cell metabolism and low insulin levels can cause catabolism of body fat.

A. It converts glucose into glycogen for storage in the liver and muscles.

This statement is partially true, but not the main role of insulin.

Insulin does stimulate the formation of glycogen from glucose in the liver and muscles, but this is not its primary function. Glycogen is a form of stored glucose that can be mobilized when blood glucose levels are low. Insulin also inhibits the breakdown of glycogen (glycogenolysis) and the synthesis of glucose from amino acids and fatty acids (gluconeogenesis) in the liver.

B. It breaks down glucose into carbon dioxide and water for excretion in the urine and lungs.

This statement is false.

Insulin does not break down glucose, but rather facilitates its uptake by cells.

Glucose is broken down by a process called glycolysis, which produces pyruvate and ATP (energy).

Pyruvate can then enter the Krebs cycle and the electron transport chain to produce more ATP, carbon dioxide and water. Carbon dioxide is exhaled by the lungs and water is excreted by the kidneys.

Insulin has no direct role in these processes.

D. It stimulates glucose synthesis from amino acids and fatty acids in the liver.

This statement is false.

Insulin does not stimulate glucose synthesis, but rather inhibits it.

Glucose synthesis from non-carbohydrate sources, such as amino acids and fatty acids, is called gluconeogenesis.

This process occurs mainly in the liver and is stimulated by glucagon, a hormone that opposes insulin. Gluconeogenesis helps to maintain blood glucose levels when dietary intake or glycogen stores are low. Insulin suppresses gluconeogenesis by inhibiting the enzymes involved in this pathway.