Read How Respiration Connects Its Pathways
Respiration is a connected network: carbon moves through glycolysis, the link reaction and TCA cycle, while reducing equivalents feed oxidative phosphorylation.
Living-system questions are solved by matching a structure or organism to its function, process and stated condition.
Place the stages
Glycolysis occurs in cytosol; pyruvate oxidation and the TCA cycle occur in the mitochondrial matrix; oxidative phosphorylation is on the inner mitochondrial membrane. In prokaryotes, respiratory pathways occur in cytoplasm and at the plasma membrane.
Track carbon and redox
Per glucose, two CO₂ are released by the link reaction and four by two TCA turns. PGAL, malate and pyruvate oxidation are redox steps; succinyl-CoA to succinate instead couples to substrate-level phosphorylation.
Respiration is amphibolic
Intermediates can be withdrawn for biosynthesis, and pathways are regulated by product feedback. Glycerol enters glycolysis as dihydroxyacetone phosphate; amino-acid carbon skeletons can enter at different TCA intermediates.
Connect glycolysis, the TCA cycle, and the electron-transport system
For the linked pathway diagram, identify glycolysis, the TCA cycle, and the electron-transport system before following numbered arrows. Glycolysis supplies pyruvate and reducing equivalents; the TCA cycle releases CO₂; the ETS uses electrons and oxygen to form water. Under the question's conventional ATP bookkeeping, the keyed losses are 36 ATP, 12 H₂O formed, and 0 CO₂ used by the TCA cycle.
OlympIQ exam lens
- ✓Inner membrane, not outer membrane: oxidative phosphorylation.
- ✓Six CO₂ released per glucose in complete aerobic oxidation.
- ✓Succinyl-CoA → succinate is not a redox step.
- ✓Intermediates serve biosynthesis as well as breakdown.
One pathway-diagram question in this cluster remains practice-only until its quantitative arrow mapping is independently verified; the seven linked questions represent 7 of 8 clustered items (88%).
Ready to try the pattern?
100% coverage across the 8 linked questions.
Practise 8 linked questions