451 http://www4.ncsu.edu/~knopp/BCH451/e98c4.htm
BCH Fall 1998 Exam #4
Go to each question within the exam an circle or write in the subquestion (choice) that your are to answer based on the column that you circled. If you answer the wrong subquestion, you will not get any credit for that question. Please ask for help, if you are unsure about this. 1. (4) For the step given by the number in row labeled A in the glycolytic pathway, name the enzyme, give the class of the enzyme, draw the structures of the non-cofactor substrate(s) and product(s) connected by the reaction arrow(s), show reversibility or irreversibility by the directions of the arrow(s), show co-substrates coming in and out of the reaction as appropriate with the usual abbreviations, and list all other cofactors under the reaction arrow.
Enzyme name: Enzyme class: Reaction:
1. (4) For the step given by the number in row labeled B in the Krebs cycle, name the enzyme, give the class of the enzyme, draw the structures of the non-cofactor substrate(s) and product(s) connected by the reaction arrow(s), show reversibility or irreversibility by the directions of the arrow(s), show co-substrates coming in and out of the reaction as appropriate with the usual abbreviations, and list all other cofactors under the reaction arrow.
Enzyme name: Enzyme class: Reaction:
1. For the letter in row C, fill in the following blanks for that complex in oxidative phosphorylation, using full names and not abbreviations: (0.3) full and complete name: (0.2) number of protons pumped out of complex: (0.4) substrates [no structures]: (0.4) products [no structures]: (0.6) cofactors/prosthetic group(s):
1. (3.6) Give the balanced reaction for the complete oxidation of acetyl CoA in the absence of oxygen:
2. (1) For the previous question, what difference does the presence of oxygen make?
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1. [Puzzler] 1. (1.5) What three shuttle but non-TCA enzymes would be expected to be found in the cell as multiple isozymes: 1. 2. 3. 2. (1) What non-shuttle and non-TCA enzyme would be expected to be found in the cell as multiple isozymes and why:
2. (2.1) Except for the following enzymes, glycolysis and gluconeogenesis is identical.
These enzymes in glycolysis are replaced
by these enzymes in gluconeogenesis
1. For the adjacent figure which is from your textbook:
1. 2. 3. 4. 5. 6. 7.
(0.3) What biochemical system is being studied in this experiment [What would be the title for this figure]? (0.5) What would be an appropriate identity of the substrate [what could be used as the substrate]? (0.5) In Panel A, why is there no change in the curve before substrate is added? (0.5) In Panel A, why is there no change in the curve after substrate is added but before ADP is added? (0.5) In Panel A, why is there a change in the curve after ADP is added? (0.5) In Panel A, why did this change stop? (0.5) In Panel B, why was ADP NOT added?
2. The dreaded multiple choice: 1 point maximum each -0.2 minimum point each. For the following questions, circle the SINGLE number which corresponds to the BEST answer. Read each answer very carefully and completely. These questions will be graded with partial credit (both positive and negative values) so that really wrong answers will count AGAINST you.
1. Galactose enters the glycolytic pathway as this first step using 1. Galactose-1-phosphate using hexokinase 2. Galactose-6-phosphate using galactokinase 3. Galactose-1-phosphate using galactose phosphate transferase 4. Galactose-6-phosphate using hexokinase
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5. using galactokinase
1. Phosphoglycerate mutase is a transferase because 1. A phosphate group is transferred between the substrate and enzyme 2. 2,3-bisphosphate is required as a cofactor 3. The enzyme is phosphorylated prior to starting 4. The correct name is phosphoglycerate kinase 5. You can't fool me, it is a isomerase
2. Glyceraldehyde-3-phosphate dehydrogenase is an important step because 1. It provides reducing power to the mitochondria 2. It is inhibited by arsenate 3. It generates ATP 4. It traps energy in a phosphoanhydride bond 5. It has a thioester bond as an intermediate
3. Glutamate dehydrogenase is important because it 1. Provides more reducing power to generate ATPs 2. Can permit glutamate to be oxidized by the Krebs cycle 3. Incorporates ammonia into carbon compounds 4. Produces succinyl-CoA for the Krebs cycle 5. You can't fool me, it's not one of the Krebs cycle enzymes
4. Citrate can easily leave the mitochondria where as OAA can not because 1. Citrate is a tricarboxylic acid and OAA is not 2. Citrate is a regulator of glycolysis 3. Citrate is a regulator of glyconeogenesis 4. OAA is a substrate of citrate synthesis 5. You can't fool me, OAA can also leave the mitochondria
5. The role of lipoamide in pyruvate dehydrogenase is to 1. Stabilize the release of CO2 2. Oxidize pyruvate 3. Pass electrons to FAD 4. Provide electrons to acetate 5. Bind pyruvate
6. Fatty acids enter the mitochondrial matrix as the carnitine derivative because 1. CoA is very precious 2. There is a specific translocase 3. Charged molecules cannot cross the inner membrane 4. That way no energy is required 5. Two ATP equivalents are required to synthesize fatty acyl CoA
7. The chemo-osmotic theory is considered to be correct because 1. There is a proton gradient formed 2. Peter Mitchell received a Nobel prize for suggesting it 3. Complex V does exist 4. There are 2.5 ATP molecules synthesized per NADH oxidation
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5. All of the above
1. The total yield of ATP from the aerobic oxidation of glucose is calculated as follows [list in order starting from glucose]: (0.3) ATP molecules directly from this pathway: (0.3) ATP molecules indirectly from this enzyme reaction: (0.3) ATP molecules indirectly from this enzyme reaction: (0.3) ATP molecules indirectly from this enzyme reaction: (0.3) ATP molecules indirectly from this enzyme reaction: (0.3) ATP molecules directly from this enzyme reaction: (0.3) ATP molecules indirectly from this enzyme reaction: (0.3) ATP molecules indirectly from this enzyme reaction: (0.2) For a total of ATP molecules per glucose.
1. Fill in the blank(s) with full names - no abbreviations (0.3 each) Terminal electron acceptor for oxidative phosphorylation Two general items that the Krebs cycle provides Enzyme unique to the glyoxylate shunt Precise intracellular location where triacyl glycerides are synthesized and broken down How citrate leaves the mitochondria [pathway/shuttle/carrier] Intramembrane electron carrier Activators of PFK-1 Inhibitors of PFK-1 Enzyme inhibited by FEnzyme inhibited by fluoroacetate How mammals store glucose What the pentose phosphate pathway provides
Regulated enzymes in the Krebs cycle
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1. (1) Why is it necessary to store glucose?
2. (4) What happens inside of a liver cell when it is stimulated by glucagon? [You may answer in words or diagrams or a combination of both]
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