lecture 3

• What is the central role of glucose in carbohydrate metabolism?

  Glucose is the primary source of energy in carbohydrate metabolism.
• How does insulin affect blood glucose levels?

  Insulin moderates blood glucose levels by promoting glucose storage and utilization.
• What regulates insulin secretion?

  Insulin secretion is regulated by blood glucose levels and various hormones.
• What are the dietary sources that can raise blood glucose levels?

  Blood glucose levels can be raised through dietary sources, gluconeogenesis, and glycogenolysis.
• What is hyperglycaemia and its effects?

  Hyperglycaemia produces osmotic changes and cellular toxicity.
• What causes ketoacidosis?

  Ketoacidosis is caused by a lack of insulin leading to increased fat metabolism.
• What are the effects of hypoglycaemia?

  Hypoglycaemia can cause nervous irritability, fainting, convulsions, and coma if prolonged.
• What is the caloric value of carbohydrates?

  Carbohydrates provide 4 kcal/gm of energy.
• What is the caloric value of proteins?

  Proteins provide 4 kcal/gm of energy.
• What is the caloric value of fats?

  Fats provide 9 kcal/gm of energy.
• What is the primary source of energy in the fed state?

  In the fed state, glucose is the primary source of energy.
• How are fructose and galactose processed in the body?

  Fructose and galactose are converted to glucose in the liver.
• What is the predominant form of carbohydrate absorption?

  Glucose is the predominant form, accounting for ~80% of total carbohydrate absorption.
• What role do hepatocytes play in carbohydrate metabolism?

  Hepatocytes contain a large amount of glucose 6-phosphatase for carbohydrate metabolism.
• What is the final common pathway for carbohydrate transport into tissue cells?

  Glucose is the final common pathway for the transport of carbohydrates into tissue cells.
• How is glucose transported across cell membranes?

  Glucose is transported across cell membranes by facilitated diffusion.
• What is the function of glucose transporters (GLUT)?

  GLUT transporters mediate the concentration-driven uptake of glucose into various tissues.
• What is the molecular weight of insulin?

  Insulin has a molecular weight of 5808 g/mol.
• What stimulates insulin secretion?

  Insulin secretion is mainly stimulated by increased blood glucose levels.
• What is the half-life of circulating insulin?

  The circulating half-life of insulin is approximately 6 minutes.
• How does glucose regulate insulin secretion?

  Glucose regulates insulin secretion by causing a rapid rise in plasma insulin levels after a meal.
• What happens to insulin secretion when blood glucose levels decrease?

  Reduced blood glucose levels rapidly turn off insulin secretion.
• What stimulates insulin secretion besides glucose?

  Amino acids and GI hormones stimulate insulin secretion.
• How does insulin affect glucose uptake in muscle during fasting conditions?

  Under fasting conditions, muscle energy is provided by fatty acids, and GLUT4 does not take up glucose.
• How does insulin affect glucose uptake in muscle during the fed state?

  Insulin increases GLUT4 levels and glucose uptake in muscle by 15 to 20 fold.
• What happens to glucose in muscles that are active post-meal?

  Active muscles use glucose for energy generation post-meal.
• What happens to glucose in inactive muscles post-meal?

  Inactive muscles store glucose as glycogen post-meal.
• How does insulin promote hepatic glucose metabolism?

  Insulin increases glucokinase and glycogen synthetase, enhancing glucose uptake and storage.
• What happens to glycogen breakdown when insulin levels are low?

  Low insulin increases glycogen phosphorylase, promoting glycogen breakdown.
• How does insulin affect glucose metabolism in the brain?

  Insulin has minimal effect on glucose uptake by the brain, which uses glucose as its primary energy source.
• What is the normal blood glucose range?

  The normal blood glucose range is 3.4-6.2 mmol/L.
• What are the symptoms of hypoglycaemia?

  Hypoglycaemia can cause nervous irritability, fainting, convulsions, and coma if prolonged.
• What is glucagon and its molecular weight?

  Glucagon is a large polypeptide with a molecular weight of 3485 g/mol.
• What stimulates glucagon secretion?

  Glucagon secretion is stimulated by decreased blood glucose levels and increased circulating amino acids.
• How does glucagon promote glucose release from the liver?

  Glucagon receptor signaling increases cyclic AMP and PKA, stimulating glycogen breakdown.
• What inhibits glucagon secretion?

  Somatostatin inhibits glucagon secretion by exerting a general suppressive action on metabolism.
• What is the role of stress hormones in glucose metabolism?

  Stress hormones protect against hypoglycaemia by increasing glucose release and decreasing tissue glucose uptake.
• What causes Type 1 diabetes?

  Type 1 diabetes is caused by β-cell dysfunction due to viral infection, autoimmune response, or hereditary factors.
• What is the typical onset age for Type 1 diabetes?

  Type 1 diabetes typically has a juvenile onset around 14 years.
• What is Type 2 diabetes characterized by?

  Type 2 diabetes is characterized by insulin resistance and is often obesity-related.