1. Under cellular conditions, which enzyme in glycolysis has the capacity to cat
ID: 3166806 • Letter: 1
Question
1. Under cellular conditions, which enzyme in glycolysis has the capacity to catalyze a near equilibrium substrate phosphorylation requiring ADP as a substrate and also has the capacity to catalyze a near equilibrium reaction in gluconeogenesis requiring ATP as a substrate?
A.
Pyruvate Kinase
B.
PEP Carboxy Kinase
C.
Pyruvate Carboxylase
D.
Phosphoglycerate Kinase
E.
Phosphoglycerate Mutase
2. UDP-glucose pyrophosphorylase works by this mechanism:
A.
It adds a phosphate group to glucose from UDP.
B.
It adds a UMP molecule to glucose-1-phosphate by eliminating pyrophosphate.
C.
It adds a pyrophosphate group to glucose, using UTP.
D.
The phosphate group on glucose-1-phosphate becomes part of the pyrophosphate in UDP.
E.
More than one of these reactions occurs.
3. The glycogen-branching enzyme catalyzes the synthesis of branches along a growing glycogen polymer. The hydrolysis of of (?1 -> 4) linkages in glycogen has a ?G°' = -15 kJ/mol. The hydrolysis of (?1 -> 6) linkages in glycogen has a ?G°' = -7 kJ/mol. What is the net ?G°' value for the glycogen-branching enzyme?
A. -8 kJ/mol
B. 8 kJ/mol
C. -7 kJ/mol
D. 7 kJ/mol
E. none of the above.
____ 1 4. Which of the following is true of glycogen synthase?
A. The enzyme has measurable activity only in liver.
B. It catalyzes addition of glucose residues to the free end of a glycogen chain by formation of (?1 -> 4) bonds.
C. It uses UMP-glucose-6-phosphate as donor of glucose units
D. It catalyzes addition of glucose residues at branch points by formation of (?1 -> 6) bonds as well as (?1 -> 4) bonds.
E. Answers B and C are correct.
5. The following reactions all occur during oxidative decarboxylation of pyruvate, except:
A.
Removal of CO2.
B.
Formation of a high energy thioester.
C.
Addition of Coenzyme A to an acetyl group derived from pyruvate.
D.
Reduction of NAD+
E.
All of these reactions take place during oxidative decarboxylation.
A.
Pyruvate Kinase
B.
PEP Carboxy Kinase
C.
Pyruvate Carboxylase
D.
Phosphoglycerate Kinase
E.
Phosphoglycerate Mutase
Explanation / Answer
1. (D) Under the cellular condition, phosphoglycerate kinase is the enzyme in glycolysis which has the capacity to catalyze a near equilibrium substrate phosphorylation requiring ADP as a substrate and also has the capacity to catalyze a near equilibrium reaction in gluconeogenesis requiring ATP as a substrate.
2. (B) UDP-glucose pyrophosphate works by adding a UMP molecule to glucose-1-phosphate by eliminating pyrophosphate.
4. (B) The true glycogen synthase is the one which catalyzes the addition of glucose residues to the free end of a glycogen chain by formation of (alpha1 -> 4) bonds.
5. (E) All of these reactions that is the removal of CO2, the formation of a high energy thioester, the addition of coenzyme A to an acyl group and reduction of NAD+, take place during oxidative decarboxylation.
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