CHEM 153A Study Guide - Quiz Guide: Glucose-6-Phosphate Isomerase, Enolase, Glyceraldehyde 3-Phosphate Dehydrogenase

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azuremammoth471

9 Jan 2019

School

UCLA

Department

Chemistry and Biochemistry

Course

CHEM 153A

Professor

Tienson

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Document Summary

Glycolysis pathway: name the enzyme catalyzing the rate limiting step in glycolysis. Phosphofructokinase: briefly indicate what is meant by a rate-limiting step. Pep = negative effector since pep is an intermediate near the end of glycolysis that can yield atp in the pyruvate kinase reaction, high [pep] means one does not need glycolysis to proceed rapidly. Oxidoreductase: name any biological pathway(s) of which this reaction is a part. Glycolysis and gluconeogenesis: the equilibrium constant for this reaction (in the direction written) at ph 7 and 25oc is 0. 078. Briefly explain the step(s) that are involved to justify your answer. From the free energy released by the oxidation step in gapdh. With no phosphoglucose isomerase glucose-6-phosphate would not be isomerized to fructose-6-phosphate. The glucose would be harder to phosphorylate at c1, (or it could not be phosphorylated). The cleavage by aldolase would result in an asymmetrical cleavage into a 4 carbon molecule and a 2 carbon molecule.

Related Questions

Phosphofructokinase (PFK1) is a glycolytic enzyme that catalyzes the irreversible transfer of a phosphate from ATP to fructose -6-phosphate to form fructose-1, 6- bisphosphate.

fructose-6-phosphate + ATP --> fructose-1,6-bisphosphate + ADP

PFK1 is the key regulatory enzyme for glycolysis. When ATP levels are high in the cell, the cell no longer needs metabolic energy production to occur. In the case of these high energy levels, PFK1's activity is inhibited by allosteric regulation by ATP, which essentially closes the valve on the flow of carbohydrates through glycolysis.

Recall that allosteric regulators bind to a different site on the enzyme rather than the active (catalytic) site. ATP binds to the regulatory site and decreases PFK1 activity. ATP bound in the regulatory site acts as a modulator by lowering the affinity of PFK1 for its substrate, fructose-6-phosphate. AMP on the other hand, which is generated when the cell is in a low energy state binds to allosteric site and increases enzyme activity.

7. The enzyme PFK1 is an example of a non-regulatory enzyme or regulatory enzyme?

8. How is PFK regulated?

A. It is not regulated because it is a non-regulatory enzyme

B. allosteric enzyme regulation

C. covalent enzyme regulation

D. or proteolytic cleavage enzyme regulation?

9. What is the substrate and to which site on the enzyme does it bind? Which compounds are the positive and negative effectors?

10. In which conformational state would the enzyme be when negative inhibitors bind and in which conformational state would the enzyme be when positive inhibitors bind?

11. PFK1 is a heterotropic or homotropic regulatory enzyme?

12. Draw (or insert the picture from your course packet available on Canvas) the graph that corresponds to this reaction. Your graph should include the activity of PFK without bound effectors, with bound positive effector, and with bound negative effector. Label (or describe) each line to distinguish these along with which molecules are positive and negative effectors.

13. How does Vmax and K0.5 change with the positive and negative effectors?

The 6th reaction in glycolysis is catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase. This step is pivotal in the pathway because

D. coupled with the following step, it captures some of the energy of substrate oxidation as ATP

C. it represents the first of 2 substrate-level phosphorylation reactions in the pathway

E. it is the primary regulatory step for the entire pathway

B. it results in the formation of the first product with high phosphoryl transfer potential

F. it results in the formation of reducing equivalents

A. it represents the first step in the payoff phase of glycolysis

You may select zero, one, or many answers.

1. Choose the TWO correct statements describing the citrate cycle.

	ATP is an indirect product of the citric acid cycle
	Acetyl CoA can increase the pool of citric acid cycle intermediates
	Fatty acids can increase the pool of citric acid cycle intermediates
	ADP inhibits Î±-ketoglutarate dehydrogenase
	The pool of mitochondrial oxaloacetate can be increased by pyruvate
	All enzymes of the citric acid cycle are found soluble and free in the mitochondrial matrix

2.Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase?

	NADH
	H⁺
	H₂O
	FAD

3. How would a high NADH to NAD⁺ ratio be expected to affect the pyruvate dehydrogenase reaction?

	The E1 subunit is phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase decreases.
	The last step of the pyruvate dehydrogenase reaction is blocked, resulting in a decrease in activity.
	The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.
	The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an increase in pyruvate dehydrogenase activity.

CHEM 153A Study Guide - Quiz Guide: Glucose-6-Phosphate Isomerase, Enolase, Glyceraldehyde 3-Phosphate Dehydrogenase

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