Biochemistry and Nutrition: Energy Metabolism

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Questions and Answers

What is the primary role of insulin in the body?

To lower blood pressure

To catalyze the Krebs cycle

To regulate blood glucose levels (correct)

To increase blood glucose levels

Insulin secretion is solely triggered by glucose levels in the blood.

False

Which cell type in the pancreas is primarily responsible for producing insulin?

Beta (β) cells

Glucagon is primarily secreted by the ________ cells in the pancreas.

Alpha (α) Signup and view all the answers

What is the half-life of insulin?

5 minutes Signup and view all the answers

Match the hormone with its primary target organ:

Insulin = Liver Glucagon = Liver Somatostatin = Pancreas Adrenaline = Heart Signup and view all the answers

Insulin has multiple actions in liver, skeletal muscle, and fat.

True Signup and view all the answers

Describe the secretion pattern of insulin.

Biphasic manner Signup and view all the answers

What is the primary function of GLUT 4 in the body?

To enhance glucose uptake in fat and skeletal muscle cells Signup and view all the answers

Insulin deficiency leads to increased glucose uptake in various tissues.

False Signup and view all the answers

What happens to blood glucose levels when glucagon is secreted?

Blood glucose levels increase. Signup and view all the answers

Glucagon is secreted when glucose levels are less than _____ mmol/L.

4.4 Signup and view all the answers

Match the hormone with its primary effect:

Insulin = Increases glucose uptake into cells Glucagon = Stimulates glucose release from the liver Cortisol = Promotes gluconeogenesis Epinephrine = Increases blood glucose during stress Signup and view all the answers

Which transporter is responsible for glucose entry into cells that is stimulated by insulin?

GLUT 4 Signup and view all the answers

Glucagon has a longer half-life than insulin.

False Signup and view all the answers

Describe the effect of insulin on plasma glucose levels.

Insulin decreases plasma glucose levels. Signup and view all the answers

Study Notes

Biochemistry and Nutrition (RNB1: 1903) - Regulation of Energy Metabolism

The course covers the regulation of energy metabolism, specifically focusing on insulin and glucagon.
Subtopics include the brain and energy metabolism, glucagon and insulin, creatine phosphate, creatinine, glycogen, gluconeogenesis, fructose, fatty acids, the Krebs cycles, and fermentative and aerobic metabolism.

Glucagon and Insulin

These hormones regulate blood glucose levels.
Glucagon is released by pancreatic alpha cells when blood glucose is low.
Insulin is released by pancreatic beta cells when blood glucose is high.
Adipose cells take up glucose when insulin is present.
The liver breaks down glycogen into glucose when glucagon is present.
Exercise decreases blood sugar which triggers the release of glucagon.
Eating increases blood sugar triggers insulin release.

Insulin

Secreted from the pancreas in response to glucose.
75% of islet cells are beta cells that produce insulin.
Insulin secretion occurs in a biphasic manner.
The first phase involves the release of preformed secretory vesicles (5-15 minutes).
The second phase involves the release of newly synthesized insulin (30 minutes).
Insulin's half-life is short (~5 minutes).
Insulin is degraded by the liver and kidneys.
Insulin secretion is regulated by factors beyond glucose, including amino acids and glucagon-like peptide from the intestines.
Insulin's primary targets are the liver, skeletal muscle, and fat, leading to the storage of fuel (glycogen or fat).
Glucose enters cells via glucose transporters (GLUTs).
GLUT 4 is actively recruited to the cell surface in response to insulin.
Reduced glucose uptake in tissues due to insulin deficiency leads to energy starvation.
Increased glucose release from the liver due to insulin deficiency leads to hyperglycemia.
Too little glucose in cells and too much glucose in the blood are symptoms of insulin deficiency.

Insulin Secretion Mechanism

Glucose enters beta cells, triggering the increase in ATP/ADP ratio.
This closes potassium channels, causing membrane depolarization.
Calcium channels open, increasing intracellular calcium.
This increase in calcium triggers insulin secretion.
The process involves two phases: a rapid first phase and a sustained second phase.

Insulin Target Organs Effects

Liver: Glycogen synthesis, inhibition of gluconeogenesis
Muscle: Glucose uptake, protein synthesis.
Adipose Tissue: Lipogenesis, inhibition of lipolysis

Insulin Deficiency

Reduced glucose uptake, resulting in energy starvation.
Increased glucose release from the liver, leading to hyperglycemia.
These deficiencies cause too little glucose in cells and too much glucose in the blood.

Control of Glucagon Secretion

Stimuli: Low blood glucose levels, increased amino acids (arginine and alanine), sympathetic nervous system activation.
Inhibitors: High blood glucose levels, elevated insulin levels.

Glucagon

Secreted by pancreatic alpha cells.
Secreted in response to low blood glucose levels.
Target tissue is primarily the liver.
Glucagon promotes glycogenolysis (glycogen breakdown) and gluconeogenesis (glucose synthesis).
Acts synergistically with cortisol and epinephrine to raise blood glucose levels during stress.

Summary

Endocrine pancreas regulates fuel homeostasis in fed and fasting states.
Insulin is primarily secreted in response to high blood glucose levels, promoting storage.
Glucagon is secreted in response to low blood glucose levels, promoting release.

Note: This summary focuses on the provided material and may not cover all aspects of regulation of energy metabolism.

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Description

This quiz explores the regulation of energy metabolism, with a focus on the roles of insulin and glucagon in managing blood glucose levels. Key topics include the metabolic processes involving fatty acids, glycogen, and the Krebs cycle, as well as the effects of exercise and diet on hormone release. Test your understanding of these essential biochemical concepts.