Role of Hormones in Metabolism

Approximately 30 minutes after eating, what is happening in the body on a metabolic level?

About 30 minutes after eating, your blood glucose concentrations will be high. High blood glucose concentrations stimulate insulin release from beta pancreatic cells, so insulin levels should also be high. Insulin inhibits glucagon production and release so we would expect glucagon levels to be very low. Insulin also promotes anabolic processes centered around uptake of excess glucose from the bloodstream and converting it to glycogen or triglycerides for energy storage to be used later in a time of need.

Approximately 30 minutes after eating, what is happening in your body on a metabolic level?

About 30 minutes after eating, your blood glucose concentrations will be high. High blood glucose concentrations stimulate insulin release from beta pancreatic cells, so insulin levels should also be high. Insulin promotes anabolic processes centered around uptake of excess glucose from the bloodstream and converting it to glycogen or triglycerides for energy storage to be used later in a time of need.

Which of the following does NOT occur after eating a meal that is high in carbohydrates?

Correct Answer Insulin inhibits glycogen breakdown, or glycogenolysis, because insulin is released when blood glucose levels are high (i.e., when the body does not need more glucose).

What is the proper sequence of events that occurs after fasting for a couple of hours?

Glucagon binds to G-protein coupled receptors in the plasma membrane, which initiates an intracellular signaling cascade to inhibit anabolic processes and promote catabolic processes. The first catabolic process will be breakdown of glycogen, which is the fastest way to release glucose into the blood during times of fasting. Once the glycogen stores have been exhausted, liver cells will begin synthesizing glucose from other sources like proteins and triglycerides in a process known as gluconeogenesis.

Which of the following is a trigger of glucagon release?

Glucagon release is triggered by low insulin concentrations.

Which of the following best explains how high blood glucose levels trigger insulin release?

Glucose is used to produce ATP, which triggers ATP dependent potassium channels to close and potassium to build up. Potassium buildup then triggers an influx of calcium, which is the stimulus for insulin release.

How does glucose get inside the cell?

Insulin binds to transmembrane cell surface receptors and initiates an intracellular signaling cascade that results in GLUT4 transporters being inserted in the plasma membrane to allow glucose to enter the cell via facilitated diffusion.

Which of the following roles does insulin play in the body? Select all that apply.

Insulin promotes upregulation of glycolysis by supplying cells with a rich supply of glucose from the bloodstream via GLUT4 transporter expression. Insulin upregulates glycogen synthesis in the liver. This allows the liver cells to store extra glucose that they can release later when blood glucose gets too low

You are studying blood samples taken from untreated diabetic patients throughout the day. In which samples do you expect to find the peptide hormones insulin and glucagon?

Patients who have type 1 diabetes are unable to produce insulin and so, if left untreated, would not be expected to have detectable levels of insulin in their bloodstream. Patients with type 2 diabetes produce fully functioning insulin but their cells do not respond to it. Glucagon production is not affected by diabetes, so we would expect to find glucagon in blood samples of patients with type 1 and type 2 diabetes who are fasting.

What is happening at the metabolic level several hours after eating?

Several hours after a meal, blood glucose levels will be low and insulin levels will also be low. Low insulin levels will trigger pancreatic alpha cells to secrete glucagon. Glucagon promotes catabolic processes such as proteolysis, glycogenolysis, and lipolysis that release energy.

Place the following terms in order for glucagon mediated lipolysis:

The correct answer is: Activation of PKA, hormone-sensitive lipases activated, lipases hydrolyze triglycerides, and, finally, free fatty acids released into the bloodstream. Glucagon activates protein kinase A, which then activates hormone-sensitive lipases in adipose tissue. These lipases, in turn, hydrolyze triglycerides to release free fatty acids and glycerol into the bloodstream.

Which of the following inhibits insulin release?

This answer is correct. Norepinephrine is an important hormone in the "fight or flight" response. It inhibits "rest and digest" activities in order to divert all energy consuming processes to those involved with fighting off a threat or fleeing from that threat. The fight or flight response works to increase blood glucose levels, which is the opposite of what insulin wants to accomplish. Therefore, the presence of norepinephrine inhibits insulin secretion.

GLUT4 transporters move glucose into the cell via:

This is the correct answer. Glucose is brought into the cell via facilitated diffusion through GLUT4 transport channels. Facilitated diffusion differs from simple diffusion in that some sort of transport channel is used whereas simple diffusion is completely unassisted transport across a membrane. Facilitated diffusion is not listed as an answer choice so "none of the above" is the correct answer.

What is the primary force driving glucose into the cell?

This is the correct answer. With the presence of protein channels, glucose is able to move down its concentration gradient and enter the cell via facilitated diffusion.

True or false: Insulin promotes lipolysis and amino acid uptake for protein synthesis, which contributes to insulin's overall effect of promoting energy storage rather than energy release. True

This statement is false. The first part of this statement about lipolysis is incorrect. Insulin downregulates lipolysis (breakdown of lipids) and promotes lipid storage by increasing triglyceride synthesis. It does this by telling adipocytes, or fat cells, to absorb more fatty acids from lipoproteins that are circulating in the blood. Once adipocytes get these extra fatty acids, they simply link them using glycerol to form triglycerides and shunt them straight into storage. In light of this, it logically follows that insulin opposes the breakdown of triglycerides into their fatty acid components by downregulating lipolysis. The second part of this statement about amino acids is correct. Insulin acts to prevent proteolysis, which is protein breakdown. On the flip side, it also helps cells absorb amino acids from the blood that they can use to build new proteins. The common thread linking these various effects is that insulin promotes energy storage, rather than energy use and release. Because the first part of the statement is incorrect, the entire statement must be labeled as false.

True or false: Insulin and glucagon are produced by pancreatic beta cells and pancreatic alpha cells, respectively.

This statement is true. Insulin is produced by beta cells in the pancreas. Glucagon is produced by alpha cells in the pancreas.

Which of the following promote insulin release?

You may recall that acetylcholine is the main neurotransmitter in the parasympathetic nervous system, which is responsible for "rest and digest" functions. Since insulin promotes glucose uptake and storage after you eat, it makes perfect sense that parasympathetic input is involved. Pancreatic beta cells are also stimulated by the digestive enzyme cholecystokinin, which also fits with the "rest and digest" state.

hormone involved in fight or flight that inhibits insulin

norepinephrine