Biochemistry: Metabolism & Hormones Study Quiz
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Questions and Answers

What are the two main types of tissues in the pancreas?

The acini and the islets of Langerhans

Which cells in the islets of Langerhans secrete glucagon?

  • PP cells
  • Alpha cells (correct)
  • Delta cells
  • Beta cells

    • What is the name of the small protein synthesized in the beta cells of the pancreas?

    Insulin

    Which of the following is NOT a metabolic effect of insulin?

    <p>Increased gluconeogenesis in the liver</p> Signup and view all the answers

    Insulin is secreted when there is a lack of energy-giving foods in the diet.

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

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

    <p>6 minutes</p> Signup and view all the answers

    Which type of receptor is the insulin receptor?

    <p>Enzyme-linked receptor</p> Signup and view all the answers

    What is the name of the group of intracellular enzymes targeted by the insulin receptor?

    <p>Insulin receptor substrates (IRS)</p> Signup and view all the answers

    Insulin promotes the conversion of excess glucose into ______ and inhibits gluconeogenesis in the liver.

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

    The brain cells are permeable to glucose and can use glucose without the intermediation of insulin.

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

    What is the term used to describe the breakdown of glycogen into glucose?

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

    What is the primary effect of glucagon on blood glucose levels?

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

    What hormone is secreted by the delta cells of the islets of Langerhans?

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

    Somatostatin is the same chemical substance as growth hormone inhibitory hormone.

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

    Which of the following is NOT a factor that stimulates somatostatin secretion?

    <p>Decreased blood glucose</p> Signup and view all the answers

    What are the two main types of diabetes mellitus?

    <p>Type 1 and Type 2 diabetes mellitus</p> Signup and view all the answers

    What is the primary cause of Type 1 diabetes?

    <p>Autoimmune destruction of beta cells</p> Signup and view all the answers

    Type 2 diabetes is more common than Type 1 diabetes.

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

    Match the following features of diabetes with their corresponding type.

    <p>High plasma glucose = Type 1 High plasma insulin = Type 2 Insulin therapy = Type 1 Weight loss = Type 2 Obesity = Type 2 Reduced insulin sensitivity = Type 2</p> Signup and view all the answers

    What is the term used to describe the condition of having a high level of insulin in the blood?

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

    Insulin shock is a serious condition that can result in coma and death.

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

    What is the primary treatment for insulin shock?

    <p>Administration of glucagon</p> Signup and view all the answers

    What is the term used to describe a condition where individuals experience accumulation of excess body fat?

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

    Which of the following is NOT a potential health consequence of obesity?

    <p>Improved bone density</p> Signup and view all the answers

    What is the name of the commonly used indirect measure of body fat?

    <p>Body Mass Index (BMI)</p> Signup and view all the answers

    The two main types of obesity are exogenous and endogenous.

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

    Which of the following is NOT a characteristic of hyperplastic obesity?

    <p>Fairly good long-term weight reduction response</p> Signup and view all the answers

    What is the term used to describe a condition where excess fat is located in the central abdomen?

    <p>Android obesity</p> Signup and view all the answers

    Gyniod obesity is characterized by a waist-to-hip ratio greater than 0.8 for men.

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

    Which of the following is NOT a potential cause of obesity?

    <p>Efficient nutrient absorption</p> Signup and view all the answers

    What is the term used to describe the breakdown of fats into fatty acids and glycerol?

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

    Insulin resistance in adipose tissue can increase the level of free fatty acids.

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

    Obesity can worsen insulin resistance by increasing the production of insulin.

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

    What is the term for the chemical structures of vitamins?

    <p>The chemical structures of vitamins</p> Signup and view all the answers

    Vitamins are essential for maintaining healthy cells, tissues, and organs.

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

    Vitamins are chemicals found in ______ amounts in many different foods.

    <p>very small</p> Signup and view all the answers

    Water soluble vitamins can be stored in human tissues.

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

    What are the two main categories of vitamins based on their solubility?

    <p>Fat soluble and water soluble vitamins</p> Signup and view all the answers

    Which of the following is a fat-soluble vitamin?

    <p>Vitamin K</p> Signup and view all the answers

    What is the name of the membrane protein involved in photoreception in the retina?

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

    Vitamin D is sometimes called the "sunshine vitamin."

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

    What is the biologically active form of vitamin D?

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

    What is the primary function of vitamin E?

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

    What is the other name given to vitamin K?

    <p>Anti-hemorrhagic vitamin</p> Signup and view all the answers

    Vitamin B1 is also known as the "anti-neuritic factor."

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

    What is the coenzyme form of Vitamin B1?

    <p>Thiamin pyrophosphate (TPP)</p> Signup and view all the answers

    Vitamin B2 (Riboflavin) is known as the "Beauty vitamin."

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

    What is the other name for vitamin B5?

    <p>Pantothenic acid</p> Signup and view all the answers

    Vitamin B6 is a water-soluble vitamin.

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

    Which of the following is NOT a function of vitamin B9?

    <p>Calcium absorption</p> Signup and view all the answers

    Vitamin C deficiency can lead to scurvy.

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

    Study Notes

    Biochemistry Study Notes

    • Course Theme: Integration of Metabolism, Metabolic Effects of Insulin and Glucagon, The Feed/Fast Cycle, Diabetes Mellitus, Obesity, Nutrition, Vitamins

    • Reading Materials: Lippincott's Illustrated Reviews: Biochemistry - 5th ed. by Harvey, Richard; Ferrier, Denise, pages 305-371

    • Assessment Type: Written Exam, Oral Exam

    • Pancreas Function: The pancreas has digestive functions and secretes hormones like insulin and glucagon crucial for normal glucose, lipid, and protein metabolism. Other hormones include amylin, somatostatin, and pancreatic polypeptide.

    • Pancreatic Islets: The pancreas contains 1 to 2 million islets of Langerhans organized around capillaries. These islets contain three major cell types:

      • Alpha cells (25%): Secrete glucagon
      • Beta cells (60%): Secrete insulin and amylin, mainly in the middle of the islet.
      • Delta cells (10%): Secrete somatostatin
      • PP cells (small numbers): Secrete pancreatic polypeptide

    • Insulin and its Metabolic Effects:

      • Insulin was first isolated in 1922 by Banting and Best.
      • It's a small protein, synthesized in beta cells.
      • Affects carbohydrate, fat, and protein metabolism.
      • Normal insulin action affects hepatic glucose production, utilization, and glycogenesis.
      • Insulin-resistance state causes hyperglycemia and hyperinsulinemia.

    • Insulin's Role in Energy Abundance:

      • Insulin secretion is triggered by high carb intake.
      • It stores excess carbs as glycogen (primarily in liver and muscle).
      • It converts carbs into fats stored in adipose tissue.
      • It promotes amino acid uptake and protein synthesis, while inhibiting protein breakdown.

    • Insulin Chemistry and Synthesis:

      • Insulin is a polypeptide with two amino acid chains linked by disulfide bridges.
      • When separated, the functional activity of insulin is lost.
      • Insulin circulates unbound to carrier proteins with a short half-life (∼6 minutes).
      • Approximately half of blood insulin is metabolized in the liver, while the remainder is metabolized by the kidneys

    • Insulin Activation and Cellular Effects:

      • To initiate effects, insulin binds to and activates membrane receptor proteins.
      • The receptor is a tetramer with two alpha subunits (outside) and two beta subunits (inside).
      • Autophosphorylation of beta subunits activates intracellular enzymes (e.g., IRS).
      • Insulin then controls intracellular metabolic machinery to affect carbohydrate, fat, and protein metabolism.

    • Effect of Insulin on Carbohydrate Metabolism:

      • Insulin rapidly causes glucose uptake, storage, and use in most tissues, especially muscle, adipose, and the liver.

    • Insulin & Muscle Glucose Uptake: Muscle tissue uses fatty acids for energy, but can use glucose during exercise or after a meal.

    • Insulin & Liver Glucose Uptake: The liver stores glucose as glycogen when absorbed from blood; insulin regulates these processes. Insulin inhibits liver phosphorylase (used to break down glycogen) for glycogen storage. Insulin enhances glucose uptake via glucokinase initially phosphorylating glucose

    • Glucose Release from Liver: Low blood glucose level results in decreased insulin secretion. The absence of insulin leads to phosphorylase activation leading to glucose phosphate creation which then becomes activated by insulin for additional glucose production

    • Insulin and Fat Metabolism: Insulin promotes converting excess glucose into fatty acids and inhibiting gluconeogenesis in the liver. Excess glucose leads to fat packaging as triglycerides into VLDL which is transported to adipose tissue for fat deposition.

    • Lack of Effect of Insulin on Glucose Uptake by the Brain: The brain can use glucose without insulin's mediation

      • Low blood glucose (~20-50 mg/100 ml) can lead to hypoglycaemic shock, with symptoms like irritability, fainting, seizures and coma.

    • Effect of Insulin on Other Cells: Insulin enhances glucose transport into most body cells, including adipose cells (contributing to fat deposition), but not the brain.

    • Insulin Promotes Fat Synthesis and Storage:

      • Insulin enhances glucose utilization in the tissues.
      • Insulin stimulates fatty acid synthesis in the liver.
      • Fatty acids are transported to adipose cells for storage.

    • Insulin Deficiency and Fat Metabolism:

      • Without enough insulin, the body breaks down stored fat to a much greater degree.
      • The consequential increase in free fatty acids results in energy production in nearly all tissues, but not the brain.
      • Higher concentrations of acetoacetic acid and β-hydroxybutyric acid are released from the liver resulting in ketosis and acidosis

    • Excess Usage of Fats During Insulin Lack:

      • Excess acetoacetic acid converting to beta-hydroxybutirric acid and acetone.
      • The accumulated ketones in the body fluids is ketoacidosis, a state increasing the risk of coma or death.

    • Effect of Insulin on Protein Metabolism:

      • Insulin promotes protein synthesis and storage during the few hours after a meal.
      • It stimulates transport of amino acids (e.g., valine, leucine) into cells.
      • It increases mRNA translation for new protein formation.
      • Insulin inhibits protein breakdown and encourages the preservation of amino acids in body protein stores.
      • Deficiency of insulin causes loss of proteins and increases plasma amino acids.

    • Insulin and Growth Hormone Interaction

      • Insulin and growth hormone interact to promote growth in a synergistic fashion, promoting growth in different ways.

    • Mechanism of Insulin Secretion:

      • Glucose enters beta cells via GLUT-2, triggering phosphorylation to glucose-6-phosphate by glucokinase.
      • Subsequent ATP production closes ATP-sensitive potassium channels.
      • This depolarization opens calcium channels, leading to insulin release via exocytosis.

    • Other Factors Stimulating Insulin Secretion: Increased blood glucose, free fatty acids, amino acids, gastrointestinal hormones (gastrin, cholecystokinin), glucagon, growth hormone, cortisol, parasympathetic stimulation, and B-adrenergic stimulation.

    • Other Factors Decreasing Insulin Secretion: Decreased blood glucose, fasting, somatostatin, alpha-adrenergic activity, and leptin.

    • Role of Insulin & Other Hormones in "Switching" Between Carbohydrate and Lipid Metabolism: Blood glucose concentration controls switching; low glucose suppresses insulin secretion and promotes fat use. Conversely, high glucose stimulates insulin secretion and promotes carbohydrate use.

    • Glucagon and its Functions: Secretion is triggered by low blood glucose levels. The functions are diametrically opposed to insulin. It increases blood glucose levels by breaking down glycogen, increasing gluconeogenesis. It also enhances fatty acid mobilization to increase available substrate

    • Glucagon's Other Effects: Activates adipose cell lipase to increase available fatty acids, inhibits liver triglyceride storage, and (in high concentration) enhances cardiac and kidney function, increases bile secretion, and inhibits gastric acid secretion

    • Regulation of Glucagon Secretion: Increased blood glucose inhibits glucagon secretion, but decreased blood glucose levels lead to an increase. High amino acid presence stimulates glucagon secretion, while exercise also does.

    • Somatostatin's Role:

      • It is secreted by delta cells of the islets of Langerhans.
      • It has a short half-life (~3 minutes).
      • It inhibits insulin and glucagon secretion, and decreases motility of the stomach, duodenum, and gallbladder, as well as GIT secretion and absorption
      • Its role is to extend the period during which nutrients are assimilated into the blood.

    • Blood Glucose Regulation Information: The blood glucose level is carefully controlled within 80-90mg/100ml in the morning. In response to feeding, glucose rises from 80-90 to 120-140mg/100ml during the first hour after the meal and the glucose level returns to the control level within 2 hours.

    • Regulation of Glucose Levels During Hypoglycemia: Severely decreased blood glucose triggers sympathetic nervous stimulation and consequent increased epinephrine signaling to increase hepatic glucose production. Prolonged hypoglycemia leads to increased cortisol signaling and growth hormone, decreasing glucose utilization in the body and directing energy production toward fatty acid utilization to return to normal blood glucose level.

    • Importance of Glucose Regulation: Glucose is the only primary source of energy for the brain, retina, and gonads; excessive glucose causes osmotic pressure leading to dehydration, and excessive concentration of glucose in the blood may impair the proper functioning of the organs

    • Diabetes Mellitus: A syndrome of impaired carbohydrate, fat, and protein metabolism. Two types:

      • Type 1 (IDDM): Impaired insulin secretion which can be caused by autoimmune destruction of the beta cells. Patients usually develop symptoms in early adulthood, are lean and need insulin for treatment.
      • Type 2 (NIDDM): Insulin resistance, meaning target tissues do not respond normally to insulin which is commonly associated with obesity (excess adipose tissue, especially in the abdominal cavity around internal organs), which develops slower than Type 1.
        • Type II characteristics: High but variable age at onset; obesity; normal to high initial plasma insulin; high plasma glucose; reduced tissue response to insulin; need for drugs or weight loss.

    • Type I Diabetes: Lack of insulin production in beta cells of the pancreas results in symptoms like frequent urination, excessive thirst, and weight loss. Chronic high blood glucose concentration damages multiple tissues, potentially leading to nerve damage, cardiovascular complications, kidney problems, retinopathy, blindness, and gangrene.

    • Type II Diabetes: Characterized by decreased responsiveness of tissues to the effects of insulin in a more gradual fashion; typically associated with conditions like obesity, and hyperinsulinemia but normal morphology of the beta cells for a while; can cause various symptoms.

    • Insulin Treatments:

      • Type 1 diabetes often requires daily insulin injections.
      • Type 2 diabetes may be treated with lifestyle adjustments (diet, exercise) and/or medications that enhance insulin activity or increase insulin secretion.

    • Insulin Shock and Hypoglycemia:

      • The sudden reduction in blood glucose levels below 50-70mg/100ml, and especially 20-50 mg/100ml, from an excessive insulin dose to individuals with insulin-secreting tumours or high doses of insulin and causes hypoglycemia
      • Treatment involves immediate intravenous glucose administration as well as glucagon or epinephrine to promote glycogenolysis and enhance glucose availability.

    • Obesity: Characterized by an excessive accumulation of body fat. The accumulation of fat is a result of the energy taken in by food exceeding that used in normal metabolic processes.

    • Obesity Types: Exogenous (overeating, decreased activity), Endogenous (hormonal, metabolic, hypothalmic issues).

    • Pathological Types: Hyperplastic (increased cell numbers, lifelong, responsive to weight loss) and Hypertrophic (increased cell size, often adult onset, potentially reversible with weight loss).

    • Obesity Types (distribution): Android (upper body), Gynoid (lower body)

    • Metabolic changes during obesity: Insulin resistance in adipose tissue increases hormonal sensitive lipase which leads to increased FFA, TAGS and cholesterol. Hyperinsulinism in the liver causes more TAGS, which leads to hypercholesterolemia. Increase FFA mobilization, and reduced glucose utilization.

    • Classification of Vitamins: Fat-soluble (A, D, E, K) and water-soluble (C, B complex).

    • Vitamin details: Information about all the vitamins (chemical structures, dietary sources, functions, mechanism of action).

    • References: List of cited resources for accurate facts.

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    Description

    Test your understanding of the integration of metabolism and the metabolic effects of insulin and glucagon. This quiz covers essential topics such as the feed/fast cycle, diabetes mellitus, obesity, and the roles of vitamins. Dive into the functions of the pancreas and the hormonal interplay critical for metabolic processes.

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