CH. 15 HW Flashcards
The activity of the glycolytic enzyme phosphofructokinase-1 is increased by which one of the following molecules?
Fructose-2,6-bisphosphate
ATP
Fructose-1,6-bisphosphate
Fructose-6-phosphate
Fructose-2,6-bisphosphate
In the glycolytic pathway ATP is synthesized by which one of the following methods
Phosphorolysis
Oxidative phosphorylation
Substrate-level phosphorylation
Photophosphorylation
Substrate-level phosphorylation
What is the typical fate of pyruvate in red blood cells?
Reduced to produce lactate.
Converted to ethanol and CO2.
Used to produce glucose via gluconeogenesis.
Completely oxidized to CO2 and H2O.
Reduced to produce lactate.
Which one of the following is not involved in the reactions of glycolysis between glyceraldehyde-3-phosphate and 3-phosphoglycerate?
Use of inorganic phosphate.
Oxidation of NADH.
The formation of a high energy intermediate.
Generation of ATP.
Catalysis by a kinase enzyme
Oxidation of NADH.
Which of the following is a method of directly regulating PFK-1?
Feed forward activation by phosphoenolpyruvate.
By its phosphorylation in response to glucagon signaling.
Feedback inhibition by fructose-2,6-bisphosphate.
Allosteric activation by ADP.
Allosteric activation by ADP.
Which pair of curves, on the graph shown, best represents the behaviour of pyruvate kinase in i) the absence, and ii) the presence of ADP?
Absence = 2, and presence = 3
Absence = 1, and presence = 2
Absence = 3, and presence = 4
Absence = 4, and presence = 3
Absence = 4, and presence = 1
Absence = 4, and presence = 3
Which of the following statements about the reaction catalyzed by hexokinase is FALSE?
Hexokinase is competitively inhibited by its product.
Hexokinase desolvates glucose to speed up the rate of the reaction.
Hexokinase undergoes a conformational change when glucose binds at the active site.
Hexokinase catalyses a substrate-level phosphorylation reaction.
Hexokinase catalyses a substrate-level phosphorylation reaction.
**This statement is FALSE. Hexokinase catalyzes the transfer of a phosphate from ATP to glucose, which is classified as a phosphate transfer reaction. A substrate-level phosphorylation is the direct transfer of a phosphoryl group to ADP generating ATP
Which statement completes the following sentence correctly? The reactions in glycolysis catalyzed by phosphofructokinase-1 and pyruvate kinase are similar in that:
they both use ATP.
they are both catalyzed by allosteric enzymes.
they are both reversible.
they are both substrate-level phosphorylation reactions.
they both involve three-carbon compounds.
they are both catalyzed by allosteric enzymes.
Which enzyme catalyzes a regulated step in glycolysis and is affected by insulin?
A. Hexokinase
B. Phosphofructokinase-2
C. Fructose-1,6-bisphosphatase
D. Phosphofructokinase-1
Both C and D are correct.
Phosphofructokinase-1
What is the net energy gain when 1 molecule of dihydroxyacetone phosphate is converted to pyruvate?
1 mol of NADH + 2 mols of ATP
1 mol of NADH + 1 mol of ATP
2 mols of NADH + 4 mols of ATP
2 mols of NADH + 2 mols of ATP
1 mol of NADH + 4 mols of ATP
1 mol of NADH + 2 mols of ATP
If radioactively labeled inorganic phosphate (32Pi) is added to a cell-free liver extract, which of the following molecules will become radiolabeled during glycolysis?
A. Phosphoenolpyruvate
B. glyceraldehyde-3-phosphate
C. 1,3-bisphosphoglycerate
D. ATP
Both C and D are correct.
Both C and D are correct.
If pyruvate could not be converted to lactate in muscle cells during strenuous exercise, what would be the outcome?
Glycolysis would stop.
The rate of gluconeogenesis will increase.
Glycolysis would be more efficient.
The muscle cell would export pyruvate out of the cell.
Glycolysis would stop.
Biochemically, why is ethanol produced by yeast?
Ethanol replaces acetyl-CoA as the main substrate for the citric acid cycle.
Cytoplasmic NADH is reoxidized sustaining glycolysis under anaerobic conditions.
The accumulation of acetaldehyde, which is toxic, is prevented.
Its production facilitates the transport of reducing equivalents into the mitochondria.
Cytoplasmic NADH is reoxidized sustaining glycolysis under anaerobic conditions.
How much carbon dioxide is produced from the complete aerobic catabolism of fructose-1,6-bisphosphate?
4 molecules CO2
0 molecules CO2
3 molecules CO2
5 molecules CO2
6 molecules CO2
6 molecules CO2
Glucose is converted to ______ in skeletal muscle under anaerobic conditions.
lactose
The enzymes that catalyze glycolysis are located in the _______
cytosol
Phosphofructokinase is allosterically _____ by high concentrations of _____.
I. activated; ATP
II. inhibited; ATP
III. inhibited; fructose-2,6-bisphosphate
IV. activated; fructose -2,6-bisphosphate
I, III
II, III
II, IV
I, IV
none of the above
II, IV
In alcoholic fermentation, acetaldehyde is produced by
the decarboxylation of pyruvate.
the carboxylation of pyruvate.
the decarboxylation of lactate.
the carboxylation of lactate.
none of the above
the decarboxylation of pyruvate.
The metabolism of mannose requires _____ to produce ____ for entry into the glycolytic pathway.
hexokinase; glucose-6-phosphate
hexokinase; fructose-6-phosphate
phosphomannose isomerase; glucose-6-phosphate
phosphomannose isomerase; fructose-6-phosphate
phosphofructokinase; bisphosphoglycerate
phosphomannose isomerase; fructose-6-phosphate
If glucose labeled at the C-1 position with 14C passes through glycolysis, on which carbon of pyruvate will the radiolabel be found?
1
2
3
It will be released in CO2 rather than present in pyruvate.
Not enough information is given to predict.
3
Which of the following is a method of directly regulating PFK-1?
Allosteric activation by ADP.
By its phosphorylation in response to glucagon signaling.
Feedback inhibition by fructose-2,6-bisphosphate.
Feed forward activation by phosphoenolpyruvate.
Feed forward activation by phosphoenolpyruvate.
Pyruvate has several metabolic fates depending on the cell, under aerobic or anaerobic conditions. Which one of the following is a metabolic fate for pyruvate?
decarboxylation to oxaloacetate
oxidation to ethanol
reduction to lactate
oxidative carboxylation to acetyl-CoA
reduction to lactate
Which of the following is NOT a direct product of pyruvate metabolism?
A. Acetyl-CoA
B. Lactate
C. Oxaloacetate
D. Phosphoenolpyruvate
Both C and D are correct.
D. Phosphoenolpyruvate
**Pyruvate cannot be converted to phosphoenolpyruvate by reversal of the pyruvate kinase reaction of glycolysis.
The rate of glucose consumption in yeast is dramatically different if the yeast are grown in the presence of oxygen as compared to yeast grown under anaerobic conditions. What would this difference be?
Yeast grown anaerobically consume 10 times less glucose.
Yeast grown anaerobically consume 19 times more glucose.
Yeast grown anaerobically consume 10 times more glucose.
Yeast grown anaerobically consume 19 times less glucose
Yeast grown anaerobically consume 19 times more glucose
**CORRECT. Yeast grown anaerobically consume more glucose as they only generate 2 ATP per glucose molecule.
