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Intermediates can be withdrawn for biosynthesis, and pathways are regulated by product feedback.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.
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- ✓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%).
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