カタボリズム１５

Question 1

The two stages of Glycolysis are:

Answer 1

Stage 1: Glucose is activated by phosphorylation by ATP and broken down into two C3 sugars.
Stage 2: High-energy intermediates are produced and they phosphorylate ADP to form ATP.

Question 2

Overall equation for Glycolysis is:

Answer 2

Glucose + 2NAD^+ + 2ADP + 2Pi = 2 pyruvate + 2NADH + 2ATP + 2H2O + 4H^+

Question 3

Steps in Stage 1 of Glycolysis:

Answer 3

1. Glucose —hexokinase+ATP–> G6P
2. G6P —phosphoglucose isomerase–> F6P
3. F6P —PFK+ATP–>FBP; irreversible, rate-determining step
4. FBP—aldolase—> GAP + DHAP; cleaved into two C3 compounds.
5. DHAP —triose phosphate isomerase—>GAP;
   interconversion of DHAP and GAP. Essentially, 2 GAPs are formed in Stage 1 of Glycolysis.

Question 4

Rate determining step in Glycolysis:

Answer 4

Step 4 of Stage 1: F6P —PFK + ATP —> FBP

Question 5

Steps in Stage 2 of Glycolysis:

Answer 5

1. GAP + NAD^+ —GAPDH—> 1,3-BPG + NADH; 1,3-BPG is high-energy
2. 1,3-BPG + ADP —phosphoglycerate kinase—> 3PG +ATP; first ATP product of glycolysis
3. 3PG —phosphoglycerate mutase—> 2PG
4. 2PG —enolase—> PEP + H2O; PEP is high energy
5. PEP + ADP —pyruvate kinase—> pyruvate + ATP; second ATP product of glycolysis
6. Repeat 1-5 for second GAP

Overall: produced 4 ATP, net 2 ATP since used 2ATP in Stage 1.

Question 6

High-energy intermediates in Glycolysis:

Answer 6

1,3-BPG and PEP; both made in Stage 2 of Glycolysis and use their energy to phosphorylate ADP to replenish ATP

Question 7

Most of the free energy of pyruvate kinase reaction involving PEP and ADP is supplied by:

Answer 7

PEP transferring phosphoryl group and leftover enol product tautomerizing to keto form(pyruvate)