Question

The following substrate is completely oxidized to CO₂ by a cellular homogenate containing all necessary enzymes and coenzymes. It is assumed that glycolysis, the citric acid cycle and oxidative phosphorylation are fully active and that the glycerol-3-phosphate shuttle is functional. What is the net gain of ATP molecules after the complete degradation of Dihydroxyacetone phosphate?

Answer 1

# Dihydroxy acetone phosphate

ATP molecules produced in glycolysis;

- Glyceraldehyde 3 phosphate dehydrogenase step produces 1 NADH2 that produces 2 ATPs.

- Phosphoglycerate kinase step produces 1 ATP.

- Pyruvate kinase step produces 1 ATP.

TCA Cycle;

- Pyruvate dehydrogenase step produces 1 NADH2 that produces 2 ATPs.

- Isocitrate dehydrogenase step produces 1 NADH2 that produces 2 ATPs.

- Alpha keto- glutarate dehydrogenase produces 1 NADH2 that produces 2 ATPs.

- Succinate dehydrogenase step produces 1 FADH2 that produuces 2 ATPs.

- Succinate thiokinase produces 1 ATP.

- Malate dehydrogenase step produces 1 NADH that produces 2 ATPs.

Since all the NADH2 molecules are entering through glycerol-3- phosphate shuttle only 2 ATPs are forming from each NADH2.

Total ATP production = 2+ 1+ 1+ 2+ 2+ 2+ 2+ 1+ 2 = 15 ATPs.

Complete oxidation of dihydroxyacetone phosphate produces 15 moles of ATP.