Metabolic Fuel Regulation
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Questions and Answers

What is the effect of adrenaline on insulin secretion?

  • Inhibits insulin secretion (correct)
  • Stimulates insulin secretion
  • Increases the storage of insulin in the pancreatic β cell
  • Has no effect on insulin secretion

    • What is the primary function of glucagon in the body?

  • To inhibit the uptake of amino acids
  • To prevent hypoglycaemia after a protein meal (correct)
  • To promote the synthesis of fatty acids
  • To stimulate the storage of glycogen

    • What is the result of insulin stimulating glycogen synthesis and storage?

  • Increased storage of fatty acids
  • Increased breakdown of glycogen
  • Increased uptake of amino acids
  • Increased storage of glucose in the form of glycogen (correct)

    • What is the effect of high concentrations of amino acids in the blood on glucagon secretion?

    <p>Stimulates glucagon secretion</p> Signup and view all the answers

    What is the result of insulin stimulating fatty acid synthesis and storage from CHO?

    <p>Increased storage of fatty acids</p> Signup and view all the answers

    What is the structure of the insulin receptor?

    <p>A heterotetrameric structure with two α-subunits and two β-subunits</p> Signup and view all the answers

    What is the primary function of the α subunit of the insulin receptor?

    <p>To bind insulin</p> Signup and view all the answers

    What is the effect of insulin on hormone-sensitive lipase in adipocytes?

    <p>Inhibition</p> Signup and view all the answers

    What is the downstream target of PI3 kinase that promotes glucose uptake?

    <p>Akt/PKB</p> Signup and view all the answers

    What is the role of Ras in insulin signaling?

    <p>Activation of MAPK</p> Signup and view all the answers

    What is the effect of insulin on glucose transport in muscle and adipose tissue?

    <p>Stimulation</p> Signup and view all the answers

    What is the role of the β subunit of the insulin receptor?

    <p>Phosphorylating IRS</p> Signup and view all the answers

    What is the effect of insulin on glycogen synthesis in muscle and liver?

    <p>Stimulation</p> Signup and view all the answers

    What is the role of Akt/PKB in insulin signaling?

    <p>Inhibition of GSK</p> Signup and view all the answers

    What is the effect of insulin on gene expression?

    <p>Stimulation</p> Signup and view all the answers

    What is the role of IRS in insulin signaling?

    <p>Activating PI3 kinase</p> Signup and view all the answers

    What is the characteristic of GLUT receptors in brain, liver, and erythrocyte?

    <p>Insulin-independent</p> Signup and view all the answers

    What happens to insulin receptors when insulin concentrations are high?

    <p>Down-regulation of receptors</p> Signup and view all the answers

    What is the primary function of glucagon in the liver during fasting?

    <p>Glycogenolysis</p> Signup and view all the answers

    What is the effect of adrenaline on muscle and liver during stress?

    <p>Stimulates glycogenolysis</p> Signup and view all the answers

    What is the primary function of cortisol in muscle during fasting?

    <p>Mobilizes amino acids</p> Signup and view all the answers

    What is the characteristic of liver carbohydrate metabolism during the fed state?

    <p>Glycogen synthesis is activated</p> Signup and view all the answers

    What is the effect of insulin on fatty acid metabolism in the liver during the fed state?

    <p>Activates fatty acid synthesis</p> Signup and view all the answers

    What is the characteristic of glucose metabolism in the brain and erythrocyte?

    <p>Relies on glucose</p> Signup and view all the answers

    What is the primary function of insulin in the body?

    <p>To regulate blood glucose levels by promoting glucose uptake</p> Signup and view all the answers

    Which of the following hormones has a hyperglycaemic effect?

    <p>Glucagon</p> Signup and view all the answers

    What is the approximate percentage of pancreatic mass comprised of islets of Langerhans?

    <p>2%</p> Signup and view all the answers

    Which enzyme is phosphorylated in response to insulin stimulation?

    <p>Glycogen phosphorylase</p> Signup and view all the answers

    What is the primary factor that stimulates insulin secretion?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is NOT a mechanism by which the body achieves changes in metabolic pattern?

    <p>Changes in gene expression</p> Signup and view all the answers

    What is the approximate number of islets of Langerhans present in the adult pancreas?

    <p>1 million</p> Signup and view all the answers

    Which hormone provides fine-tuning of blood glucose homeostasis by stimulating insulin secretion?

    <p>Glucagon</p> Signup and view all the answers

    Study Notes

    Fuel Metabolism and Hormone Regulation

    • The body's fuel demand is constant, but the supply is intermittent.
    • Hormones regulate fuel metabolism by storing fuel when it's available and mobilizing it in times of starvation, injury, or stress.

    Hormones Controlling Intermediary Metabolism

    • Insulin and glucagon are the primary regulators of metabolism.
    • Insulin is the only hypoglycemic hormone, while glucagon is a hyperglycemic hormone.
    • Other insulin counter-regulatory hormones include adrenaline, cortisol, and growth hormone.

    Islets of Langerhans

    • The islets of Langerhans are the endocrine part of the pancreas, making up about 2% of the total pancreatic mass.
    • The adult pancreas contains around 1 million islets.
    • β cells (60-70%) secrete insulin, α cells (30-40%) secrete glucagon, and δ cells secrete somatostatin.

    Insulin Secretion and Regulation

    • Insulin secretion is stimulated by a rise in blood glucose, amino acid concentration, and gut hormones.
    • Glucagon also stimulates insulin secretion, providing fine-tuning of blood glucose homeostasis.
    • Insulin secretion is inhibited by adrenaline.

    Glucagon Secretion and Regulation

    • Glucagon secretion is stimulated by low blood glucose, high amino acid concentration, and adrenaline.
    • Glucagon secretion is suppressed by insulin.

    Metabolic Effects of Insulin

    • Insulin promotes fuel storage after a meal, growth, and glycogen synthesis and storage.
    • Insulin stimulates fatty acid synthesis and storage from carbohydrates when intake exceeds glycogen storage capacity.
    • Insulin stimulates amino acid uptake and protein synthesis.

    Insulin Receptor Structure and Signaling

    • The insulin receptor consists of α and β subunits, with the α subunit binding insulin and the β subunit containing a docking site for IRS.
    • Insulin binding activates the tyrosine kinase, leading to phosphorylation of IRS and activation of PI3 kinase.
    • PI3 kinase activates Akt/PKB, which promotes glucose uptake and glycogen synthesis.

    Metabolic Effects of Glucagon

    • Glucagon mobilizes fuel, maintains blood glucose during fasting, and activates glycogenolysis, gluconeogenesis, and fatty acid release from adipose tissue.

    Adrenaline and Cortisol

    • Adrenaline mobilizes fuel during stress, stimulating glycogenolysis and fatty acid release from adipose tissue.
    • Cortisol provides for long-term requirements, stimulating amino acid mobilization from muscle, gluconeogenesis, and fatty acid release from adipose tissue.

    Blood Glucose Regulation

    • Blood glucose levels, insulin, and glucagon vary after a high-carbohydrate meal and over 24 hours of normal eating behavior.
    • Insulin and glucagon work together to maintain blood glucose homeostasis.

    Metabolism in the Fed State

    • The fed state occurs 2-4 hours after a meal, characterized by an increase in blood glucose, amino acids, and TAG as chylomicrons.
    • The liver is essential in this state, receiving nutrients from the hepatic portal vein before other tissues.
    • Glycogen synthesis, glycolysis, and fatty acid synthesis are activated in the liver, while gluconeogenesis is inhibited.

    Liver Carbohydrate Metabolism

    • The liver is engaged in gluconeogenesis at all times except the fed state, when glycolysis is activated through glucokinase.
    • Glycogen synthesis is activated, and glycogen synthase is phosphorylated.
    • Glycolysis is activated through PFK and pyruvate kinase.

    Liver Fat Metabolism

    • Fatty acid and TAG synthesis are activated in the liver, with acetyl-CoA carboxylase as the rate-limiting step.
    • Malonyl-CoA inhibits carnitine transferase, directing newly synthesized FA towards TAG synthesis.

    Brain and Erythrocyte Metabolism

    • Both the brain and erythrocytes rely on glucose for energy.

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    Description

    This quiz covers how the body regulates metabolic fuel storage and mobilization in response to changing hormone concentrations, and the mechanisms involved in achieving metabolic pattern changes.

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