GNG and PPP Practice Questions KEY PDF

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Ch 22 – Gluconeogenesis Practice Questions 1. Why is regulation of the reaction of fructose 6-phosphate and fructose 1,6-bisphosphate so important in balancing glycolysis and gluconeogenesis? Draw both structures and indicate the enzymes responsible for the conversion between the two metabolites.

F1,6BPase opposes PFK1, yet both reactions are favorable and can occur without achieving a metabolic goal. Regulation of these enzymes is so important to make sure that energy is not being wasted and that the correct pathway is turned on and the other inhibited or turned off, such that needed molecules are produced for cellular demands. 2. Which residue plays a critical role in the mechanism of Glucose-6-Phosphatase? a. His b. Cys c. Asp d. Ser e. Tyr 3. Which two pathways tie together to give rise to the Cori Cycle and what is the common molecule that connects the two? Anaerobic glycolysis (glu→lactate) and gluconeogenesis (lactate→glucose) 4. As a result of the Cori Cycle, what two important molecules are regenerated? What can these molecules now be used for? Glucose and NADH, Glucose and NADH can be used further in anaerobic glycolysis to produce more ATP quickly for muscle tissue 5. Draw the mechanism for pyruvate carboxylase. What coenzyme is required or this enzyme and what is its purpose? Biotin serves as the CO2 carrier, mechanism is Figure 22.3 (page 723) or lecture 3, slide 19

6. Draw the pathway from 2 lactates to glucose as it occurs in gluconeogenesis. Show the structures and names of all reactants and products, as well as the names of the enzymes. You do not need to draw the structures of ATP, NAD+, CoA, etc., but do show them as reactants or products in the appropriate places. You do not need to show the mechanisms of the enzymes. O

2

HO

O-

C

+

2 ADP + 2Pi +4H+

2 ATP +2 H2O

O

2 2

H3 C

O

O

C

C

-

O

O

O

C

C

H2 C

C

2GTP

O-

Phosphoenol pyruvate carboxykinase

2 NADH + 2 H+

2GDP

Lactate Dehydrogenase 2-

PO 3

2 NAD+ OH

O

C

C

O

2

H3 C

O-

Pyruvate Carboxylase

2

O-

2

+

C

H2C

O

O

C

C

O-

H O

2H2O Enolase O

O

2

2 ADP

2-

C

2 ATP

O

OPO 3

O-

C

Phosphoglycerate Mutase

2 OH

HC

H2 C

Phosphoglycerate Kinase

2OPO3

HC

2-

OPO3

2

OH

HC

O-

C

H2 C

2-

OPO3

H2 C

2 NADH O

OH

-

O H

P

O

O

H2 C

2 NAD+ + Pi O

O

2

Triose phosphate Isomerase

H

OH

OH

H

OH

O

OH

H2C

H2O

Fructose 1,6-bisphosphatase

2-

H2 C

2-

OPO3

OPO3

Pi

O-

CH 2OH

Pi

O

P

H2O

O-

OO

H O

P

O H2C

CH 2

O

O-

O

O H

OH OH

OH

H

OH

OH

H

OH H

OH

Glucose 6-phosphatase

OH

OH

OH OH

P O-

H

Aldolase C

HC

H

OH

H2 C CH

O

O

-

Phosphoglucose isomerase

OH

O

-

Ch 22 – Pentose Phosphate Pathway Practice Questions

Consider the following course metabolism that is shown above. 7. What metabolic demands are being met?? Need for NADPH (biosynthesis) and ATP (energy) 8. What pathways are being utilized? Pentose phosphate pathway gives NADPH and glycolytic pathway for ATP. Ribose 5-phosphate formed by the oxidative phase of the pentose phosphate pathway can be converted into pyruvate. Fructose 6-phosphate and glyceraldehyde 3-phosphate derived from ribose 5phosphate enter the glycolytic pathway rather than reverting to glucose 6-phosphate. In this mode, ATP and NADPH are concomitantly generated, and five of the six carbons of glucose 6phosphate emerge in pyruvate. 9. Draw the mechanism for the enzyme phosphopentose epimerase. Indicate names of all reactants, substrates, and intermediates.

10. Cellular demands require production of NADPH. Which of the following enzymes is involved in the oxidative portion of the pentose phosphate pathway to produce NADPH? a. 6-Phosphogluconate Dehydrogenase b. Phosphopentose Isomerase c. Transaldolase d. Transketolase e. All of the above...