Highly Likely Test Questions and Answers PDF

Highly Likely Test Questions and Answers Glycogenesis Q: What is glycogenesis, and where does it occur? A: Glycogenesis is the synthesis of glycogen from glucose, occurring in the cytosol. It requires energy supplied by ATP and UTP. Q: What are the two types of glycosidic bonds in glycogen, and...

Highly Likely Test Questions and Answers Glycogenesis Q: What is glycogenesis, and where does it occur? A: Glycogenesis is the synthesis of glycogen from glucose, occurring in the cytosol. It requires energy supplied by ATP and UTP. Q: What are the two types of glycosidic bonds in glycogen, and what are their roles? A: - alpha-1,4 linkages: Form straight chains. - alpha-1,6 linkages: Form branches, allowing for faster glycogen breakdown. Q: What is the role of glycogenin in glycogenesis? A: Glycogenin acts as a primer to initiate glycogen synthesis by accepting glucose residues from UDP-glucose. Q: How are branches formed in glycogen, and what is the role of the branching enzyme? A: Branches are formed by the branching enzyme, which transfers 6-8 glucose residues to form alpha-1,6 linkages. Glycogen Stores and Functions Q: Where is glycogen stored in the body, and what are its functions in the liver and muscle? A: Glycogen is stored in: - Skeletal muscle: Provides energy for muscle contraction. - Liver: Maintains blood glucose levels during fasting. Q: How does glycogen storage differ between liver and muscle? A: Liver glycogen maintains blood glucose levels for the body, while muscle glycogen is used locally for energy during muscle contraction. Glycogenolysis Q: What is glycogenolysis, and what triggers it? A: Glycogenolysis is the breakdown of glycogen into glucose, triggered by fasting, exercise, or hormones like glucagon and adrenaline. Q: What is the role of glycogen phosphorylase in glycogenolysis? A: Glycogen phosphorylase cleaves alpha-1,4 glycosidic bonds, releasing glucose 1-phosphate. Q: How are branches removed during glycogenolysis, and what is the role of the debranching enzyme? A: Branches are removed by the debranching enzyme, which has: - 4:4 transferase activity (transfers residues to another chain). - Amylo-alpha(1,6)-glucosidase activity (cleaves the branch point). Q: Why can muscle glucose 6-phosphate not be converted to free glucose? A: Muscle lacks glucose 6-phosphatase, the enzyme required to convert glucose 6-phosphate to free glucose. Glycogen Storage Diseases Q: What are glycogen storage diseases (GSDs), and what causes them? A: GSDs are inborn errors of metabolism caused by enzyme deficiencies, leading to abnormal glycogen accumulation. Q: What are the clinical features of Von Gierke's disease (Type I GSD)? A: Type I GSD is caused by glucose 6-phosphatase deficiency, leading to fasting hypoglycemia, lactic acidosis, hyperlipidemia, and hyperuricemia. Q: What enzyme deficiency causes McArdle's disease, and what are its symptoms? A: McArdle's disease is caused by a deficiency of muscle phosphorylase, resulting in muscle cramps and inability to perform strenuous exercise. Glucose Homeostasis Q: What is the normal fasting blood glucose level and post-meal range? A: Fasting blood glucose: 74-106 mg/dL. Post-meal blood glucose: 100-140 mg/dL. Q: What is the role of insulin in glucose homeostasis? A: Insulin lowers blood glucose by: - Promoting glycogenesis. - Enhancing glucose uptake. - Stimulating glycolysis. Q: What is the role of glucagon in regulating blood glucose levels? A: Glucagon raises blood glucose by: - Stimulating glycogenolysis. - Promoting gluconeogenesis. Q: What is the function of diabetogenic hormones in glucose homeostasis? A: Diabetogenic hormones (growth hormone, glucocorticoids, adrenaline) increase blood glucose by antagonizing insulin effects. Diabetes Mellitus Q: What are the types of diabetes mellitus, and how do Type 1 and Type 2 differ? A: - Type 1: Autoimmune destruction of beta-cells, leading to absolute insulin deficiency. - Type 2: Insulin resistance with relative insulin deficiency. Q: What biochemical changes occur in diabetes mellitus? A: Biochemical changes include: - Hyperglycemia: Excess glucose in the blood. - Lipid abnormalities: Increased free fatty acids and ketone production. - Protein metabolism: Muscle protein breakdown. Q: How does diabetes affect lipid metabolism? A: Diabetes increases lipolysis, leading to elevated free fatty acids, ketone body production, and dyslipidemia. General and Integration Q: Why are carbohydrates considered a major source of energy? A: Carbohydrates provide quick energy via glycolysis and the citric acid cycle, with glucose serving as the primary energy source for most cells. Q: How are glycogenesis and glycogenolysis regulated in the liver and muscle? A: - Liver: Glycogenesis occurs in the well-fed state; glycogenolysis during fasting. - Muscle: Glycogenesis occurs during rest; glycogenolysis during exercise. Q: What enzymes are involved in glycogen metabolism? A: - Glycogenesis: Glycogen synthase and branching enzyme. - Glycogenolysis: Glycogen phosphorylase and debranching enzyme. Q: How is glycogen metabolism connected to blood glucose regulation? A: Liver glycogen is broken down to glucose during fasting to maintain blood glucose levels, linking glycogenolysis to homeostasis.