anim_carbohydrate_metabolism_answer_key.doc

Carbohydrate Metabolism To complete this worksheet, select: Module: Energy Acquisition Activity: Animations Title: Carbohydrate Metabolism Introduction 1. a. What happens to most carbohydrates during digestion? Carbohydrates are hydrolyzed into monosaccharides, mostly glucose. b. What is the relationship between glucose and ATP production? The catabolism of glucose is the primary source of energy for cellular production of ATP. c. Describe the importance of glucose anabolism. The anabolism of glucose is important in regulating blood glucose levels. Glucose Catabolism 2. Identify the four “pathways” of glucose catabolism. a. Glycolysis. b. Formation of acetyl co-enzyme A. c. Kreb’s cycle. d. Electron transport chain. 3. Why is glycolysis referred to as anaerobic while the remaining four pathways are aerobic? Because glycolysis can take place in the absence of oxygen. The formation of acetyl co-enzyme A, the Kreb’s cycle and the electron transport chain all require oxygen to proceed. Glycolysis 4. Where within the cell does glycolysis occur? It occurs within the cytosol of the cell. 5. a. Glucose is a six carbon carbohydrate. What happens to this molecule in the first step of glycolysis? The glucose molecule is split into two 3-carbon compounds and phosphorylated into dihydroxyacetone phosphate and glyceraldehydes – 3 phosphate.This process requires 2 ATP molecules. b. What is produced by the remainder of the glycolytic pathway? The remaining glycolytic pathway produces 2 ATP molecules, 2 NADH molecules and two molecules of pyruvic acid. Formation of acetyl coenzyme A 6. What is formed by the oxidation of each pyruvic acid molecule? A molecule of acetyl co-enzyme A. 7. How do the two acetyl group molecules form? These arise by reducing NAD to NADH+ and removing a CO2 thus forming an acetyl group. How does acetyl coenzyme A form? The resulting acetyl group links with coenzyme A forming acetyl coenzyme A. Krebs Cycle 9. Where does the Krebs Cycle occur? Within the mitochondrion of the cell. 10. How many carbon dioxide molecules are produced from each acetyl CoA molecule as a by-product of the Krebs Cycle? Two molecules of CO2 11. How many ATP are produced from the Krebs Cycle? Two molecules of ATP. 12. What is the function of reduced coenzymes produced by the Krebs Cycle (NADH)? The reduced enzymes that are produced by the Kreb’s cycle will enter into the electron transport system where they can give up their electrons and be oxidized back to NAD Electron Transport Chain 13. a. What does the electron transport chain do with the energy stored in the reduced coenzymes? The energy from the oxidizing NADH + H+ is used to pump hydrogen ions across the inner mitochondrial membrane. b. Where does this pathway occur? Along the inner mitochondrial membrane 14. a. Describe how hydrogen ion concentrations increase inside the inner mitochondrial membrane. Hydrogen ions are pumped across the inner mitochondrial membrane resulting in the formation of a hydrogen ion concentration gradient between the inner and outer matrix of the mitochondrion. b. What by-product is formed by the oxidation of the coenzymes? Carbon dioxide. 15. Describe the movement of hydrogen ions and the resulting synthesis of ATP, a process known as chemiosmosis. The hydrogen ion flows down the concentration gradient producing the force needed for a special protein channel, ATP synthetase to synthesize ATP from ADP. Summary of Glucose Catabolism 16. Complete this chart for each part of glucose catabolism. Show totals at the bottom. Glucose Anabolism 17. Where does glycogenolysis occur? In the Liver. 18. a. What hormones stimulate glycogenolysis? Glucagon from the pancreas and human growth hormone from the anterior pituitary as well as thyroxin. b. What is occurring during glycogenolysis? Glycogen is converted into glucose which is subsequently released into the bloodstream thus increasing blood levels of sugar. a. What occurs during glycogenesis? Glucose is polymerized into glycogen. b. What hormone stimulates glycogenesis? Insulin from the pancreas. 20. a. What is the function of glyconeogenesis? To convert substances that are not carbohydrate based, such as proteins and lipids, and convert them into sugar. b. Where does this process occur? In the liver. c. What hormones stimulate it? Glucagon from the pancreas, thyroxin from the thyroid gland and human growth hormone from the anterior pituitary. d. How does glyconeogenesis affect blood glucose levels? Glucose is made from non-carbohydrates based substances and enter the blood stream increasing blood levels.