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Exam 3 Sample Questions - ANSWERS page 1 ANSWERS TO SAMPLE QUESTIONS FOR BIOC 460 - EXAM 3 Lecture 22 – METABOLISM: BASIC CONCEPTS Starvation is the nutritional state during which gluconeogenesis provides blood glucose. False Glycogen is an example of a circulating fuel. (It is stored.) Among the following substances the one with the highest phosphate group transfer potential is: D. phosphoenolpyruvate Glycerol-3-phosphate Adenosine diphosphate (ADP) Glucose-1-phosphate Adenosine monophosphate (AMP) Guanosine triphosphate (GTP) 0 high energy phosphate bonds 1 high energy phosphate bond 0 high energy phosphate bonds 0 high energy phosphate bonds 2 high energy phosphate bonds The intermediate common to all major carbohydrate pathways is: glucose-6-phosphate The major fuel for the brain in the postabsorptive state is: glucose Lecture 23 – SIGNAL TRANSDUCTION: G-PROTEINS TRUE TRUE Binding of GTP to the αS subunit of GS ultimately leads to the activation of protein kinase A. Binding of glucagon to its receptor ultimately leads to the activation of protein kinase A. Identify two second messengers whose formation is associated with activation of a G protein CYCLIC AMP (cAMP) or DIACYLGLYCEROL (DAG) or INOSITOL TRISPHOSPHATE (IP3) Describe the mechanism for the inactivation of the kinase that is involved in glucagon signal transduction through phosphorylation of a variety of enzymes in metabolic pathways. The kinase is protein kinase A. Since it is activated by binding of cyclic AMP to the regulatory subunit then inactivation requires hydrolysis of cyclic AMP by phosphodiesterase. Once cyclic AMP disappears, the regulatory subunit reassociates with the catalytic subunit to shut it off. A phosphodiesterase can catalyze the hydrolysis of: C. cyclic AMP. In the phosphoinositide cascade: A. protein kinase C is activated by diacylglycerol. Lecture 24 - DIGESTION AND ABSORPTION OF CARBOHYDRATES FALSE TRUE FALSE TRUE FALSE Cellulose is the form in which animals store carbohydrates. One product of pancreatic α-amylase is glucose. Amylopectin is the form in which animals store carbohydrates. One product of pancreatic α-amylase is α-limit dextrin. Lactase is an α-glycosidase in the intestine. Exam 3 Sample Questions - ANSWERS page 2 The GLUT-4 transporter that is stimulated by insulin is found in: C. adipose. The enzyme derived from the pancreas that hydrolyzes starch is pancreatic: C. -amylase Glucoamylase is the brush border enzyme complex that cleaves oligosaccharides and α-limit dextrins. Galactose is the only sugar that could not be absorbed from the intestinal lumen if the sodium(Na+),potassium (K+)-ATPase were defective in intestinal cells. Sucrase OR sucrase-isomaltase is the brush border enzyme that cleaves the disaccharide containing fructose and glucose. The two sugars that comprise maltose are glucose and glucose. Sucrose contains two molecules of sugar including glucose and fructose. Lecture 25 - SIGNAL TRANSDUCTION: INSULIN TRUE FALSE FALSE TRUE IRS-1 is phosphorylated before it docks with the p85-PI3K complex. The receptor subunit that contains the insulin binding site also contains the tyrosine kinase domain to facilitate its activation. Autophosphorylation sustains the binding of insulin to its receptor. The tyrosine kinase activity of the insulin receptor is located on a domain of the β-subunit. Calcium promotes the biosynthesis and processing of insulin by: E. binding to calmodulin to activate calmodulin kinase Insulin’s ability to promote glucose transport includes the phosphorylation, by the insulin receptor tyrosine kinase, of a component in the cytoplasm of adipose cells. This component is: B. IRS-1 What is the cause of Type I diabetes? -Cell destruction or unable to make insulin or autoimmune response What is generally the initiating event in Type II diabetes? Loss Of Insulin Response Or Insulin Resistance DRAW A DIAGRAM showing the steps leading to the complete activation of both tyrosine kinases of the insulin receptor Exam 3 Sample Questions - ANSWERS page 3 P P P Lectures 26/27 - GLYCOLYSIS AND GLUCONEOGENESIS In liver, the endproduct of fructose metabolism that enters the glycolytic pathway is: B. glyceraldehyde-3-phosphate. A description of the Cori cycle includes: D. gluconeogenesis from lactate in liver and glycolysis in muscle. The gluconeogenic enzyme that is activated by citrate is: B. fructose-1,6-bisphosphatase. The glycolytic enzyme that is inhibited by citrate is: A. pyruvate kinase. Identify the enzyme and its SPECIFIC ISOZYME FORM that is responsible for regenerating NAD+ during anaerobic glycolysis. Enzyme: Isozyme form: Lactate Dehydrogenase (or LDH) M4 (or all M subunits) Pyruvate carboxylase OR PC is the ATP-requiring reaction that is unique to gluconeogenesis but not to glycolysis. Fructose-2,6-bisphosphate OR F26BP is the allosteric regulator that activates glycolysis in the liver and whose concentration is controlled by hormone in response to blood glucose. Identify one glycolytic enzyme that uses ATP and one that produces ATP. uses ATP: hexokinase OR glucokinase OR phosphofructokinase-1 produces ATP: phosphoglycerate kinase OR pyruvate kinase Aspartate can be converted directly to oxaloacetate by removal of its amino group. How many molecules of high energy phosphate compounds will be consumed in converting aspartate to TEN molecules of glucose? 20 aspartate needed to make 10 glucose 20 asp to 20 oxaloacetate to 20 phosphoenolpyruvate = loss of 20 GTP 20 phosphoenolpyruvate to 10 glucose = loss of 20 ATP Net loss = 40 molecules of high energy phosphate compounds Exam 3 Sample Questions - ANSWERS page 4 Identify features of the H4 isozyme of lactate dehydrogenase that makes it different from the M4 isozyme. H4 has a high affinity (or low Km) for lactate H4 is inhibited by pyruvate H4 found in heart not anaerobic skeletal muscle Intravenous infusion of fructose into healthy volunteers increases lactate in the blood by threefold, a far greater increase than observed following the infusion of the same amount of glucose. Why is glycolysis more rapid following the infusion of fructose than glucose? Fructose metabolism bypasses phosphofructokinase-1 the rate-limiting reaction in glycolysis that glucose must use; fructose enters later at glyceraldehyde-3-P INSULIN is the hormone that activates protein phosphatase to catalyze dephosphorylation of enzymes? Hexokinase: D. transfers a phosphoryl group to a variety of hexoses Hexokinase is allosterically inhibited by D. glucose-6-phosphate. The phosphofructokinase-1 and pyruvate kinase reactions are similar in that: E. both are essentially irreversible Glyceraldehyde 3-phosphate dehydrogenase: C. produces NADH as a product. A gluconeogenic enzyme that requires GTP is: D. phosphoenolpyruvate carboxykinase (PEPCK). Starting with fructose-6-phosphate and proceeding to pyruvate what is the net yield of ATP? phosphofructokinase-1 = loss of 1ATP phosphoglycerate kinase = gain of 2ATP (fructose-1,6-bisphosphate splits to two molecules) pyruvate kinase = gain of 2ATP Net yield = gain of 3 ATP Describe how the intracellular concentration of fructose-2,6-bisphosphate is regulated by insulin. Insulin activates protein phophatase. Protein phosphatase removes the phosphate from the bifunctional enzyme phosphofructokinase-2/fructose-2,6-bisphosphatase. This leads to activation of the kinase and inhibition of the fructose bisphosphatase. Consequently fructose2,6-bisphosphate is synthesized to increase its intracellulat concentration. Lecture 28 - PYRUVATE DEHYDROGENASE/CITRIC ACID CYCLE FALSE TRUE Isocitrate dehydrogenase is activated by NADH α-Ketoglutarate dehydrogenase is inhibited by NADH In the citric acid cycle, FADH2 is formed as a product in a reaction catalyzed by: A. succinic dehydrogenase Exam 3 Sample Questions - ANSWERS page 5 In the citric acid cycle, GTP is formed as a product in a reaction catalyzed by: B. succinyl CoA synthetase For the pyruvate dehydrogenase complex identify the cofactors and their vitamin precursor Cofactor: Thiamine Diphosphate CoA (Coenzyme A) NAD FAD Vitamin: Thiamine (Vitamin B1) Pantothenic Acid (Pantothenate) Niacin Riboflavin Lectures 29/30 - OXIDATIVE PHOSPHORYLATION The outer mitochondrial membrane: E. surrounds a space that is more positively charged than the mitochondrial matrix. The inner mitochondrial membrane: A. is invaginated forming cristae. What is transported out of the mitochondrial matrix into the intramembrane space and is an example of electrogenic transport? ATP or adenosine triphosphate What is transported from the intramembrane space into the mitochondrial matrix in exchange for a negatively charged molecule and is an example of electroneutral transport? PYRUVATE or PHOSPHATE or MALATE or -KETOGLUTARATE What is complex IV of the electron transport (respiratory) chain also called? Cytochrome c oxidase Identify the characteristics of the chemiosmotic model that relates to oxidative phosphorylation impermeable inner membrane pH gradient across inner membrane asymmetry of membrane components destroying proton gradient (uncoupling) - stops ATP synthesis (or increases oxygen consumption inhibiting respiratory chain - stops ATP synthesis (or stops proton pumping) Define respiratory control: When ADP increases it activates the stalk to open the proton channel (or lower proton gradient or lower pH gradient). This increases mitochondrial respiration (or respiratory chain). Define uncoupling Destruction (dissipation, collapse) of the pH (or proton) gradient across the mitochondrial inner membrane causing loss of the ability to synthesize ATP. Define electrogenic transport. Transport systems in which a net charge moves across a membrane Complex III of the electron transport (respiratory) chain is also called: Cytochrome reductase Exam 3 Sample Questions - ANSWERS page 6 Complexes I and III of the electron transport (respiratory) chain are linked by: Coenzyme Q (ubiquinone)