Biochemistry RNB:1903 - Energy Metabolism Quiz

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Questions and Answers

What is the primary function of GLUT 4 in skeletal muscle and fat cells?

To transport fatty acids into cells

To promote glycogen breakdown

To decrease insulin sensitivity

To facilitate glucose uptake during insulin stimulation (correct)

What happens to glucose levels in the blood when there is insulin deficiency?

Blood glucose levels fluctuate wildly

Blood glucose levels increase (correct)

Blood glucose levels decrease

Blood glucose levels remain constant

How does glucagon primarily affect the liver?

It decreases fat metabolism

It causes the liver to secrete glucose (correct)

It promotes glycogen synthesis

It inhibits glucose release

What triggers the secretion of glucagon from the pancreatic alpha cells?

Fasting conditions (C) Signup and view all the answers

Which hormone acts synergistically with glucagon to raise blood glucose levels?

Cortisol (C) Signup and view all the answers

What is the role of glucose-6-phosphate in the cell?

To prevent glucose from leaving the cell (D) Signup and view all the answers

What is the half-life of glucagon in circulation?

6 minutes (A) Signup and view all the answers

What effect does insulin have on glucose levels in the body?

Increases glucose uptake into tissues (A) Signup and view all the answers

What are the primary targets for insulin in the body?

Liver, skeletal muscle, and fat (C) Signup and view all the answers

Which type of cells in the pancreas primarily produce insulin?

Beta (β) cells (D) Signup and view all the answers

What is the primary function of glucagon in the body?

To increase blood glucose levels (D) Signup and view all the answers

What is the main way insulin secretion is stimulated?

Increased plasma glucose levels (B) Signup and view all the answers

How is insulin secreted from the pancreas?

By glucose stimulated insulin secretion (GSIS) (C) Signup and view all the answers

What percentage of islet cells in the pancreas are alpha (α) cells that secrete glucagon?

20% (A) Signup and view all the answers

What is the characteristic of insulin's secretion pattern?

Biphasic release pattern (C) Signup and view all the answers

What is the half-life of insulin in the bloodstream?

Approximately 5 minutes (C) Signup and view all the answers

Study Notes

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

Course title: Biochemistry and Nutrition (RNB:1903)
Course topic: Regulation of Energy Metabolism
Instructor: Sumathy Arumugam
Date: October 27, 2028
Topics covered:

Subtopics

The brain and energy metabolism
Glucagon and insulin (22/10/2021 - 27/10/2023)
Creatine phosphate
Creatinine
Glycogen
Gluconeogenesis
Fructose
Fatty acids
The Krebs cycles
Fermentative and aerobic metabolism

Glucagon and Insulin

Why? Fasting can cause headaches due to lack of glucose. Glucose is needed for proper brain function.
Insulin's role: Adipose cells take up glucose. Decreasing blood sugar level triggers the pancreas to release insulin.
Glucagon's role: Eating causes increasing blood sugar. Pancreatic alpha cells release glucagon. The liver breaks down glycogen to glucose. Exercise decreases blood sugar, causing the release of glucagon.

Introduction

Insulin and glucagon are hormones that regulate blood glucose levels.
Glucose (from food) fuels the body by moving through the bloodstream.
Insulin and glucagon work together to maintain blood sugar levels within a normal range.

Learning Outcomes

Describe the biological actions of insulin and glucagon.
List the major target organs for insulin.
Identify the effect of insulin on the target organs.
Describe the control of glucagon secretion.
Identify the target organ for glucagon.

Description - Insulin

Pancreatic endocrine cells, located in islets, contain four cell types.
Beta cells (75%) secrete insulin.
Alpha cells (20%) secrete glucagon.
Delta cells (δ) secrete somatostatin (SRIF) inhibiting both insulin and glucagon secretion.
Glucose stimulated insulin secretion (GSIS) is the process by which insulin is secreted.
Insulin secretion occurs in a biphasic manner with an initial burst and a more gradual, sustained release. The initial burst lasts 5-15 minutes, then a second more gradual release follows, lasting 30 minutes.
The half-life of insulin is approximately 5 minutes.
Insulin is primarily degraded in the liver and kidneys.
Insulin secretion is regulated by factors other than glucose, including plasma amino acids and glucagon-like peptide from the small intestine.

Insulin Secretion Mechanism

Glucose enters the beta cells through GLUT 1/2, triggering ATP/ADP, thereby depolarizing the cell.
Open Ca2+ channels allow Ca2+ influx, causing insulin release.
Increased Ca2+ triggers two phases in insulin release. Immediately releasable pool or amplifying pathways in the second phase.

Insulin Deficiency Problems

Problems arise from reduced glucose uptake into tissues (energy starvation) and increased glucose release from the liver (hyperglycemia).
These factors lead to too little glucose in cells and too much glucose in the blood (hyperglycemia).

Positive and Negative Regulation of Insulin Secretion

Insulin secretion is influenced by feed-forward mechanisms such as glucagon-like peptide (GLP-1) and parasympathetic nervous system activity,
Negative feedback mechanisms such as sympathetic nervous system activity (SNS) and plasma epinephrine.

Effects of Insulin on Target Organs

Liver: Promotes glycogen synthesis, inhibits glycogenolysis.
Muscle: Promotes glucose uptake and protein synthesis.
Adipose tissue: Encourages lipogenesis, inhibits lipolysis.

Description - Glucagon

Glucagon is a peptide hormone secreted by pancreatic alpha cells when blood glucose levels are low (less than 4.4 mmol/L or 80 mg/dL).
Glucagon circulates unbound and has a half-life of 6 minutes.
The target tissue for glucagon is the liver. Glucagon binds to plasma membrane receptors, initiating a second messenger signaling cascade in the liver, increasing stored glycogen release in the liver.
Glucagon acts synergistically with cortisol and epinephrine to increase blood glucose levels.

Summary

The endocrine pancreas regulates fuel homeostasis in both fed and fasting states by producing insulin and glucagon.
Insulin promotes storage of excess nutrients in the fed state, targeting liver, muscle, and adipose tissue.
Glucagon promotes the movement of stored nutrients into the bloodstream in the fasting state, targeting the liver mainly.
Glucose levels regulate insulin and glucagon secretion.

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Description

Test your knowledge on the regulation of energy metabolism in biochemistry, focusing on key hormones like insulin and glucagon. Explore topics such as glycogen, gluconeogenesis, and the Krebs cycle. This quiz covers essential concepts relevant to the course 'Biochemistry and Nutrition'.