Insulin Production and Action
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Questions and Answers

Which glucose transporter is primarily responsible for the uptake of glucose in muscle and adipose tissue?

  • GLUT-2
  • GLUT-4 (correct)
  • GLUT-3
  • GLUT-1

    • What role does GLUT-5 primarily serve in the body?

  • Transport fructose (correct)
  • Transport glucose in the liver
  • Transport glucose in muscle
  • Transport glucose in the brain

    • During fasting, how does the body primarily produce glucose?

  • Glycogenolysis
  • Krebs cycle
  • Lipolysis
  • Gluconeogenesis (correct)

    • Which of the following statements about glucose homeostasis is true?

    <p>It involves both hormone regulation and storage mechanisms.</p> Signup and view all the answers

    What adverse effects can high glucose concentrations have on the body?

    <p>Damage cellular proteins</p> Signup and view all the answers

    Which hormone is primarily involved in the regulation of blood glucose levels during high glucose availability?

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

    What is glycogen primarily used for in the body?

    <p>Stored energy in liver and muscle</p> Signup and view all the answers

    Which of the following transporters is NOT insulin-dependent?

    <p>GLUT-1</p> Signup and view all the answers

    What triggers the opening of voltage-gated calcium channels during insulin secretion?

    <p>Depolarization of the cell membrane</p> Signup and view all the answers

    Which phase follows the initial surge of insulin secretion?

    <p>A plateau phase</p> Signup and view all the answers

    Which of the following is NOT a molecule that stimulates insulin secretion?

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

    What is a primary action of insulin on glucose?

    <p>Facilitates glucose transport into cells</p> Signup and view all the answers

    What is the effect of insulin on liver phosphorylase?

    <p>Inhibits its activity</p> Signup and view all the answers

    How does insulin affect fatty acid synthesis?

    <p>Increases fatty acid synthesis from excess glucose</p> Signup and view all the answers

    What is the predominant nature of insulin's actions?

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

    What effect does insulin have on free-fatty acids in adipose tissue?

    <p>Inhibits their release</p> Signup and view all the answers

    What is the primary characteristic of diabetes mellitus?

    <p>Chronic hyperglycaemia</p> Signup and view all the answers

    Which of the following describes the role of insulin in glucose metabolism?

    <p>It facilitates glucose uptake into cells</p> Signup and view all the answers

    What is one of the expected functions of glucagon in blood glucose regulation?

    <p>Stimulate gluconeogenesis</p> Signup and view all the answers

    Which classification of diabetes is characterized by an autoimmune destruction of beta cells?

    <p>Type 1 diabetes</p> Signup and view all the answers

    What factor does NOT contribute to the epidemiology of diabetes mellitus?

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

    Which of the following is a long-term complication associated with uncontrolled diabetes mellitus?

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

    What is the normal range of plasma glucose levels in healthy individuals?

    <p>3.5-8 mmol/L</p> Signup and view all the answers

    Which mechanism does NOT participate in glucose production?

    <p>Fat metabolism</p> Signup and view all the answers

    What is the primary role of glucagon?

    <p>To increase blood glucose concentration</p> Signup and view all the answers

    Which process does insulin promote?

    <p>Protein synthesis</p> Signup and view all the answers

    What effect does glucagon have on triglyceride storage in adipose cells?

    <p>It inhibits triglyceride storage</p> Signup and view all the answers

    Under what condition is glucagon released?

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

    What is the primary action of insulin on amino acids?

    <p>Stimulates their transport into cells</p> Signup and view all the answers

    In the fed state, what happens to blood glucose levels?

    <p>They rise</p> Signup and view all the answers

    What combination occurs when both insulin and glucagon are present at high levels?

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

    Which hormone is thought to regulate the assimilation of food nutrients into the blood?

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

    What is the primary effect of glucagon on metabolic processes?

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

    Which of the following hormones is known to inhibit insulin secretion directly?

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

    In which condition is there an autoimmune destruction of β-cells leading to insulin deficiency?

    <p>Type 1 Diabetes Mellitus</p> Signup and view all the answers

    What role do incretins play in glucose homeostasis?

    <p>Augment insulin secretion in response to oral glucose</p> Signup and view all the answers

    Which factor contributes to the catabolic state dominated by glucagon?

    <p>Loss of suppression of lipolysis by insulin</p> Signup and view all the answers

    What does the term 'pre-diabetic conditions' refer to?

    <p>Impaired fasting glycaemia and impaired glucose tolerance</p> Signup and view all the answers

    Which statement about Type 2 Diabetes is accurate?

    <p>It primarily results from insulin resistance.</p> Signup and view all the answers

    Which statement about the effect of catecholamines on insulin is true?

    <p>They promote glucagon secretion and inhibit insulin.</p> Signup and view all the answers

    What is a primary cause of chronic hyperglycaemia in diabetes mellitus?

    <p>Insulin deficiency and/or insulin resistance</p> Signup and view all the answers

    Type 1 diabetes is characterized by the presence of insulin resistance.

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

    What is the estimated global prevalence of diabetes mellitus?

    <p>537 million</p> Signup and view all the answers

    Insulin is produced by the ______ cells in the pancreas.

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

    Match the hormone with its primary function:

    <p>Insulin = Lowers blood glucose levels Glucagon = Raises blood glucose levels Epinephrine = Increases glucose production Somatostatin = Inhibits insulin and glucagon secretion</p> Signup and view all the answers

    Which of the following is NOT a typical complication of uncontrolled diabetes?

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

    Glucose homeostasis refers to maintaining a stable level of glucose in the bloodstream.

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

    What is the primary hormone released during periods of low blood glucose?

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

    Which glucose transporter is specifically involved in the uptake of fructose?

    <p>GLUT-5</p> Signup and view all the answers

    GLUT-4 is an insulin-independent glucose transporter.

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

    What is the process of forming glucose from non-carbohydrate molecules called?

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

    What hormone is mainly responsible for decreasing plasma glucose levels?

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

    ___________ is stored energy formed from glucose in the liver and skeletal muscle.

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

    Glycogenolysis increases blood glucose levels.

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

    Who were the scientists that identified insulin as a pancreatic extract?

    <p>Frederick Banting and Charles Best</p> Signup and view all the answers

    Match the glucose transporters to their primary tissue location:

    <p>GLUT-1 = Most cells GLUT-2 = Liver, pancreatic B cells GLUT-3 = Brain (neurons) GLUT-4 = Muscle and adipose tissue</p> Signup and view all the answers

    What is an important reason for tight control of glucose levels in the body?

    <p>Supporting brain function</p> Signup and view all the answers

    The absence of insulin contributes to the condition known as __________.

    <p>diabetes mellitus</p> Signup and view all the answers

    Hypoglycemia can be less dangerous than hyperglycemia.

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

    Which of the following factors stimulates insulin secretion?

    <p>Increased plasma glucose</p> Signup and view all the answers

    What is the term for the release and production of glucose during fasting?

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

    Match the hormones with their primary roles in glucose regulation:

    <p>Insulin = Decreases blood glucose levels Glucagon = Increases blood glucose levels Catecholamines = Promotes glycogen breakdown Cortisol = Increases plasma glucose levels</p> Signup and view all the answers

    The first patient treated with refined pancreatic extract was a 12-year-old girl.

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

    What is the primary action of insulin on glucose metabolism?

    <p>Facilitates uptake of glucose into cells</p> Signup and view all the answers

    What primarily stimulates the opening of voltage-gated calcium channels during insulin secretion?

    <p>Blood glucose levels</p> Signup and view all the answers

    Insulin secretion occurs in a single phase.

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

    What type of hormone is glucagon primarily categorized as?

    <p>Catabolic hormone</p> Signup and view all the answers

    Insulin promotes the synthesis of __________ by increasing the action of glycogen synthase.

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

    Match the following actions to their respective substances:

    <p>Insulin = Facilitates glucose transport Glucagon = Stimulates glycogenolysis Cortisol = Increases gluconeogenesis Growth Hormone = Inhibits glucose uptake</p> Signup and view all the answers

    Which of the following is NOT a molecule that can stimulate insulin secretion?

    <p>Free fatty acids</p> Signup and view all the answers

    Insulin secretion decreases as energy availability increases.

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

    Name one effect of insulin on fat metabolism.

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

    What primarily characterizes Type 1 Diabetes Mellitus?

    <p>Severe insulin deficiency due to autoimmune destruction of beta cells</p> Signup and view all the answers

    Cortisol promotes the secretion of insulin.

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

    What role do incretins play in glucose homeostasis?

    <p>They augment the secretion of insulin in response to oral glucose.</p> Signup and view all the answers

    The primary metabolic state promoted by glucagon is the ______ state.

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

    Match the following types of diabetes with their descriptions:

    <p>Type 1 = Autoimmune destruction of beta cells leading to insulin deficiency Type 2 = Insulin resistance and potential insulin deficiency Secondary diabetes = Acquired causes of diabetes due to drugs or genetic defects Pre-diabetes = Impaired fasting glycaemia and impaired glucose tolerance</p> Signup and view all the answers

    Which hormone is released during the body's 'fight or flight' response?

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

    Type 2 Diabetes typically presents in children or young adults.

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

    Name one effect of glucagon on metabolic processes.

    <p>Promotes gluconeogenesis.</p> Signup and view all the answers

    Study Notes

    Insulin Production and Secretion

    • Insulin is released from the beta cells in the pancreas in response to elevated blood glucose levels.
    • Insulin secretion is biphasic with an initial surge followed by a plateau phase that persists as long as blood glucose levels remain high.
    • Other molecules that can stimulate insulin secretion include amino acids, GI hormones, glucagon, GH, and cortisol.

    Insulin Action

    • Insulin action is mediated by the activation of the insulin receptor on the target cell membrane.
    • Insulin facilitates glucose transport into cells.
    • In muscle and adipose tissue, insulin binding causes the release of GLUT-4 transporters to the cell membrane, increasing glucose transport into cells.
    • Insulin inactivates liver phosphorylase and increases glucokinase activity, leading to enhanced glucose storage in the liver.
    • Insulin promotes glycogen synthesis by increasing glycogen synthase activity.
    • Insulin inhibits gluconeogenesis by modulating liver enzyme activities and decreasing available precursors like amino acids.
    • Insulin promotes fatty acid synthesis by converting excess glucose into fatty acids.
    • Insulin promotes fat storage in adipose cells by activating enzymes that facilitate fatty acid absorption and storage as triglycerides.
    • Insulin inhibits the release of free fatty acids from adipose tissue.
    • Insulin promotes protein synthesis and inhibits protein breakdown.
    • Insulin stimulates amino acid transport into cells.
    • Insulin inhibits gluconeogenesis by using amino acids as substrates.
    • Insulin inhibits amino acid release from cells.
    • Insulin increases RNA production and mRNA translation by activating ribosomes.

    Glucagon

    • Glucagon is a polypeptide hormone secreted by alpha cells of the islets of Langerhans.
    • Glucagon is released primarily in response to a decrease in blood glucose concentration.
    • Glucagon’s main action is to increase blood glucose concentration by stimulating glycogenolysis and hepatic gluconeogenesis.
    • Glucagon's other effects include activating adipose cell lipase to increase free fatty acid production and inhibiting triglyceride storage, increasing available free fatty acids for energy.

    Stimuli for Glucagon Release and Inhibition

    • Stimuli for glucagon release include hypoglycemia, exercise, physiological stress, and high blood amino acid concentration.
    • Glucagon release is inhibited by hyperglycemia, insulin, and somatostatin.

    Glucose Homeostasis

    • Glucose homeostasis is crucial for maintaining normal cellular function and preventing complications from high or low blood glucose levels.
    • The system regulates glucose levels in response to changes in glucose delivery (fed vs fasted) and demand (exercise or physiological stress).
    • Glucose homeostasis involves hormones, glucose storage in excess, and glucose release and production in the fasted state (glucose deficit).

    Gluconeogenesis

    • Gluconeogenesis is the formation of glucose from molecules like lactate, glycerol, glutamine, and alanine.
    • Gluconeogenesis takes place in the liver and kidneys.

    Glycogen and Glycogenolysis

    • Glycogen is a stored form of glucose in the liver and skeletal muscle.
    • Glycogenolysis is the breakdown of glycogen into glucose.

    Other Influencers in Glucose Homeostasis

    • Incretins, such as glucagon-like peptides (GLP) and gastric inhibitory peptide (GIP), are produced in the small intestine and augment insulin secretion in response to oral glucose.
    • Cortisol and growth hormone promote gluconeogenesis and inhibit glucose transport.
    • Catecholamines, released due to activation of the autonomic nervous system (fight, flight, or fright), stimulate glucagon and inhibit insulin.

    Diabetes Mellitus

    • Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia due to insulin deficiency and/or insulin resistance.
    • Type 1 diabetes is an autoimmune disease that leads to severe insulin deficiency.
    • Type 2 diabetes is caused by insulin resistance and/or less severe insulin deficiency.
    • Secondary diabetes is a term for diabetes caused by acquired factors such as drugs or genetic defects.
    • Pre-diabetic conditions include impaired fasting glycaemia and impaired glucose tolerance.

    Type 1 Diabetes Mellitus

    • Type 1 diabetes is an autoimmune disease characterized by the destruction of beta cells, leading to complete insulin deficiency.
    • Antibodies to islet cells may precede the onset of the disease by several years.
    • Type 1 diabetes typically presents in children and young adults.
    • Genetic susceptibility plays a role in the development of type 1 diabetes.

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    Description

    This quiz covers the essential aspects of insulin production and its actions in the body. It highlights the mechanisms of insulin secretion, including the role of beta cells and glucose levels, as well as how insulin facilitates glucose transport and storage. Test your understanding of insulin's effects on muscle, adipose tissue, and the liver.

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