Highly Likely Test Questions and Answers on Carbohydrate Metabolism Basics PDF

Highly Likely Test Questions and Answers Carbohydrate Metabolism Basics Q: What is the function of GluT4, and how is it regulated? A: GluT4 is a glucose transporter that facilitates glucose entry into muscle cells and adipocytes. It is regulated by insulin, which promotes the translocation of Gl...

Highly Likely Test Questions and Answers Carbohydrate Metabolism Basics Q: What is the function of GluT4, and how is it regulated? A: GluT4 is a glucose transporter that facilitates glucose entry into muscle cells and adipocytes. It is regulated by insulin, which promotes the translocation of GluT4 to the cell membrane to increase glucose uptake. Q: Which glucose transporter is insulin-independent, and where is it found? A: GluT2 is insulin-independent and is found in liver cells. It facilitates glucose uptake regardless of insulin levels. Glycolysis (Embden-Meyerhof Pathway) Q: Define glycolysis and state its significance. A: Glycolysis is the metabolic pathway in which glucose is split into two 3-carbon pyruvate molecules under aerobic conditions, or lactate under anaerobic conditions, with energy production. It is significant because: - It is the only energy pathway in red blood cells. - It provides energy during anaerobic conditions, such as exercise. - It supplies intermediates for gluconeogenesis and synthesis of amino acids. Q: List the key regulatory enzymes of glycolysis and their roles. A: - Glucokinase/Hexokinase: Catalyzes the phosphorylation of glucose to glucose-6-phosphate (Step 1). - Phosphofructokinase: Controls the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate (Step 3). - Pyruvate kinase: Converts phosphoenolpyruvate to pyruvate (Step 9). Q: What are the end products of glycolysis under aerobic and anaerobic conditions? A: - Aerobic conditions: Pyruvate and 2 ATP molecules. - Anaerobic conditions: Lactate and 2 ATP molecules. Q: How much net ATP is generated in glycolysis? A: The net ATP generated in glycolysis is 2 ATP per molecule of glucose. Gluconeogenesis Q: What is gluconeogenesis, and what are its precursors? A: Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors. Its main precursors are lactate, amino acids, and glycerol. Q: Why is gluconeogenesis critical during fasting or starvation? A: During fasting or starvation, gluconeogenesis provides a continuous supply of glucose for critical organs like the brain and red blood cells, which rely on glucose for energy. Q: What is the role of lactate in gluconeogenesis? A: Lactate is produced by skeletal muscles during anaerobic glycolysis and is transported to the liver, where it is converted back to glucose via gluconeogenesis. Citric Acid Cycle (Krebs Cycle) Q: What is the primary role of the citric acid cycle? A: The citric acid cycle is the final pathway for the oxidation of carbohydrates, amino acids, and fatty acids into carbon dioxide and water. It also produces high-energy molecules like ATP, NADH, and FADH2. Q: Describe the fate of pyruvate under aerobic conditions. A: Under aerobic conditions, pyruvate is oxidatively decarboxylated to Acetyl CoA by the pyruvate dehydrogenase complex, which then enters the citric acid cycle. Q: How many ATP molecules are generated per Acetyl CoA in the citric acid cycle? A: Each Acetyl CoA molecule produces 12 ATP molecules: 3 NADH (9 ATP), 1 FADH2 (2 ATP), and 1 GTP (1 ATP). Q: What biosynthetic intermediates are derived from the citric acid cycle? A: The citric acid cycle provides intermediates for the biosynthesis of amino acids (e.g., glutamate), fatty acids, and porphyrins. Energy Metabolism Q: Compare metabolism in the well-fed state and fasting state. A: - Well-fed state: Glucose is converted into glycogen in the liver and stored as fat in adipose tissue. Fatty acids are transported as VLDL to adipose tissues. - Fasting state: Fatty acids are broken down into ketone bodies. The liver produces glucose via gluconeogenesis to supply energy to the brain and muscles. Q: What role does the liver play in glucose metabolism during fasting? A: During fasting, the liver synthesizes glucose through gluconeogenesis and produces ketone bodies from fatty acids to provide energy for tissues. Figures and Diagrams Q: Explain the glucose absorption process shown in Figure 9.2A. A: Glucose absorption involves two transporters: - GluT1/GluT4: For intestinal glucose uptake. - GluT2: Transports glucose into the bloodstream. Q: Interpret Figure 8.2 (well-fed state metabolism). A: In the well-fed state, glucose is metabolized to glycogen in the liver. Excess glucose is converted to fatty acids and transported to adipose tissue for storage. Q: Interpret Figure 8.3 (fasting state metabolism). A: During fasting, the liver breaks down fatty acids into ketone bodies and performs gluconeogenesis to supply glucose to the brain and muscles.