Citric-acid cycle, electron-transport chain, chemiosmosis, ATP synthase, bioenergetics.
Tca Oxphos
Citric acid cycle (Krebs / TCA)
Mitochondrial eight-step cycle oxidising acetyl-CoA to 2 CO2, producing 3 NADH + 1 FADH2 + 1 GTP per turn. Central hub feeding reducing…
Pyruvate dehydrogenase complex (PDC)
Multienzyme complex (E1/E2/E3, ~50 MDa) linking glycolysis to TCA: pyruvate + CoA + NAD+ → acetyl-CoA + CO2 + NADH. Regulated by…
Electron transport chain (ETC)
Series of inner-mitochondrial-membrane complexes (I, II, III, IV) transferring electrons from NADH/FADH2 to O2, pumping protons to…
ATP synthase (F0F1)
Rotary nano-motor coupling proton flow down the electrochemical gradient to ATP synthesis. F0 (membrane c-ring) rotates; F1 (α3β3)…
Chemiosmotic theory (Mitchell)
Mitchell 1961: respiratory electron transport couples to ATP synthesis via a transmembrane electrochemical proton gradient (proton-motive…
Proton-motive force (Δp)
Electrochemical potential for H+ across the inner mitochondrial membrane: Δp = Δψ − (2.303·RT/F)·ΔpH ≈ 200 mV (negative inside).
Oxidative phosphorylation
Coupled process: ETC pumps H+ → PMF → ATP synthase uses PMF to phosphorylate ADP. ~2.5 ATP per NADH, ~1.5 ATP per FADH2 (P/O ratios, Hinkle…
Uncoupling protein (UCP1/thermogenin)
Inner-membrane proton channel that dissipates PMF as heat without ATP synthesis. Abundant in brown adipose tissue; regulated by fatty…
Anaplerotic reactions
Reactions replenishing TCA intermediates drained for biosynthesis (amino acids, heme). Pyruvate carboxylase (pyruvate → oxaloacetate) is…
Respiratory supercomplexes
ETC complexes I, III, IV assemble into higher-order 'respirasomes' (I+III2+IV or I+III2+IV2). Channel substrates efficiently; dysregulation…