Glycolysis Exercise Key
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1.

Table 1: Glycolysis reactions

For the reaction catalyzed by


the energy cost is


the energy yield is

How many times does it occur?


hexokinase

1 ATP
0
1


PFK

1 ATP
0
1


GAPDH

0
1 NADH
2


pyruvate kinase

0
1 ATP
2

2 and 3.

Table 2: Glycolysis enzymes

Enzyme

What it does
Class

hexokinase

Transfers phosphoryl group from ATP to glucose
Transferase

phosphohexose isomerase

Converts glucose-6-P to fructose-6-P
Isomerase

PFK-1

Transfers phosphoryl group from ATP to fructose-6-P
Transferase

aldolase

Splits fructose-1,6-bis-P into glyceraldehyde-3-P (GAP) + dihydroxyacetone-P (DHAP)
Lyase

triose phosphate isomerase

Converts DHAP into GAP
Isomerase

glyceraldehyde-3-phosphate dehydrogenase

Oxidizes C1 of GAP and reduces NAD+; adds phosphate to C1 of GAP
Oxidoreductase

phosphoglycerate kinase

Transfers a phosphoryl group from C3 of 1,3-bis-phosphoglycerate (1,3BPG) to ADP
Transferase

phosphoglycerate mutase

Transfers a phosphoryl group from C3 to C2 of phosphoglycerate
(3PG ↔ 2PG)
Transferase

enolase

Removes H2O from 2-phosphoglycerate
Lyase

pyruvate kinase

Transfers a phosphoryl group from phosphoenolpyruvate (PEP) to ADP
Transferase

3. There is no hydrolase or ligase in glycolysis.

4. The reactions catalyzed by PFK-1 and aldolase.

5. a. 2 ATP + 2 NADH; b. 3 ATP + 2 NADH; c. 3 ATP + 2 NADH

6. a. glyceraldehyde-3-P = GAP, enzyme = E, 1,3-bis-phosphoglycerate = 1,3-BPG
             step 1: GAP + E–SH + NAD + ↔ E–S–3PG + NADH + H+
             step 2: E–S–3PG + Pi ↔ 1,3–BPG + E–SH
b. This is important because NADH is produced, the first high energy molecule
     made in glycolysis. Because NAD+ is required for the reaction, the NADH made
     must be recycled, either by electron transport or by fermentation.

7.

8. a and b are below.
c. covalent catalysis and acid-base catalysis

9. The central carbon is reduced.
NADH produced by GAPDH is converted to NAD+ by lactate dehydrogenase.

10. The whole reaction is pyruvate + NADH + H+ ↔ lactate + NAD+ ΔE°′ = 0.135 V.
ΔG°′ = − (2) (96480 J/V-mol) (0.135 V) = − 26049.6 J/mol = − 26.0 kJ/mol.

11. A carbon is reduced.
A carbonyl is reduced in each reaction, and this is coupled to the oxidation (recycling) of NADH in each reaction.

12.

 

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