FINAL EXAM CHAPTER 16 Glycolysis

Question 1

Why is glucose such a prominent fuel molecule?

Answer 1

1. Glucose may have been available for primitive biochemical systems because it can form under prebiotic conditions.
2. Glucose is the most stable hexose
3. Glucose has a low tendency to nonenzymatically glycosylate proteins

Question 2

What are the start and end products of Glycolysis and how much ATP is extracted?

Answer 2

Converts one molecule of glucose to two molecules of pyruvate and generates two molecules of ATP

Question 3

What happens in stage 1 of Glycolysis?

Answer 3

Stage 1 traps glucose in the cell and modifies it so that it can be cleaved into a pair of phosphorylated 3-carbon compounds

Question 4

What happens in stage 2 of Glycolysis ?

Answer 4

Stage 2 oxidizes the 3-carbon compounds to pyruvate while generating two molecules of ATP

Question 5

In stage 1, what does the enzyme Hexokinase catalyze? and is this favorable or unfavorable?

Answer 5

Glucose is phosphorylated at the expense of ATP to form glucose 6-phosphate
FAVORABLE

Question 6

In stage 1,what does the enzyme phosphoglucose isomerase catalyze? And is this favorable or unfavorable?

Answer 6

Conversion of glucose 6-phosphate to fructose 6-phosphate.
NOT FAVORABLE

Question 7

In stage 1, what does the enzyme Phosphofructokinase catalyze? And is this favorable or unfavorable?

Answer 7

Carbohydrate is trapped in the fructose form by the addition of a second phosphate to form fructose 1,6-Biphosphate
FAVORABLE

Question 8

In stage 1, what does the enzyme Aldolase catalyze? And is this favorable or unfavorable?

Answer 8

It catalyzes the conversion of fructose 1-6-diphosphate to glyceraldehyde 3-phosphate(GAP) and Dihydroxyacetone phosphate(DHAP)
NOT FAVORABLE

Question 9

In stage 1, what does the enzyme Triose Phosphate Isomerase catalyze? And is this favorable or unfavorable?

Answer 9

The conversion of Dihydroxyacetone phosphate (DHAP) to glyceraldehyde 3-phosphate(GAP).
NOT FAVORABLE

Question 10

In the beginning of Stage 2, the oxidation of an Aldehyde powers the formation of which compound with High phosphoryl transfer potential?

Answer 10

1,3-Biphosphoglycerate

Question 11

In stage 2, what does the enzyme glyceraldehyde 3-phosphate dehydrogenase catalyze? And is this favorable or unfavorable?

Answer 11

The oxidation of GAP which produces 1,3-Biphosphoglycerate
NOTE here NAD+ is consumed and it has to be regenerated if glycolysis is to continue
NOT FAVORABLE

Question 12

IN the formation of 1,3-BIphosphoglycerate, what are the two steps that occur and why is an energy rich thioester required?

Answer 12

1. Highly exergonic oxidation of carbon 1 in GAP
2. Highly Endergonic formation of 1,3-Biphosphoglycerate from the acid

Energy rich thioester is required because the transition state free energy change is too large, and this will help reduce it

Question 13

In the second step of stage 2, which molecule has a higher phosphate transfer potential; than ATP and what does the enzyme phosphoglycerate kinase catalyze? And is this favorable or unfavorable?

Answer 13

-1,3-Biphosphoglycerate has higher potential so it transfers the phosphate to ADP to generate ATP and the enzyme catalyzes this reaction
FAVORABLE

Question 14

In stage 2, what does the enzyme Phosphoglycerate mutase catalyze? And is this favorable or unfavorable?

Answer 14

Conversion of 3-Phosphoglycerate into 2-phosphoglycerate
NOT FAVORABLE

Question 15

In stage 2, what does the enzyme Enolase catalyze? And is this favorable or unfavorable?

Answer 15

a dehydration reaction that results in the production of Phosphoenolpyruvate from 2-Phosphoglycerate
NOT FAVORABLE

Question 16

In stage 2, what does the enzyme Pyruvate Kinase catalyze? And is this favorable or unfavorable?

Answer 16

the phosphorylation of ADP at the expense of PEP, and this generates ATP and pyruvate.

WE are able to do the phosphorylation because PEP is a high phosphoryl transfer compound.
FAVORABLE

Question 17

How and why do we have to regenerate NAD+?

Answer 17

Because we need NAD+ for ATP synthesis.
This can be done by either further oxidation of pyruvate to CO2 or by the formation of ethanol or lactate from pyruvate.

Question 18

What is the reason for each of the molecular rearrangements?

Question 19

why might cancer cells slow glycolysis?

Answer 19

Because cancer cells express an isoform of PK called PKM2 that is less active than the normal isoform PKM1 and it causes build ups.