Glossary — Key Terms in Respiration — Notes | NoteTube

Term	Definition
Aerobic respiration	Respiration in the presence of $O_{2}$ ; complete oxidation of glucose → 38 ATP
Anaerobic respiration	Respiration in the absence of $O_{2}$ ; incomplete oxidation; only glycolysis operates
Amphibolic pathway	Metabolic pathway that serves both catabolic and anabolic functions (e.g., TCA cycle)
Acetyl CoA	2-carbon compound (acetyl group attached to coenzyme A) that enters the TCA cycle
ATP synthase ( $F_{0}$ - $F_{1}$ )	Enzyme complex in the inner mitochondrial membrane that synthesises ATP using the proton gradient
Chemiosmosis	ATP synthesis driven by the flow of $H^{+}$ down an electrochemical gradient through ATP synthase
Citrate	6-carbon first intermediate of the TCA cycle; formed by condensation of acetyl CoA + OAA
Cristae	Folds of the inner mitochondrial membrane; site of ETS complexes and ATP synthase
Cytochrome c	Water-soluble mobile electron carrier between Complex III and Complex IV in the ETS
Electron Transport System (ETS)	Series of protein complexes (I–IV) on the inner mitochondrial membrane that pass electrons to $O_{2}$
Embden-Meyerhof Pathway	Another name for glycolysis; 10-step conversion of glucose to pyruvate
Fermentation	Anaerobic process that regenerates N $AD^{+}$ from NADH; produces ethanol+C $O_{2}$ or lactate
Glycolysis	First stage of cellular respiration; 10 steps in cytoplasm; glucose → 2 pyruvate + 2 ATP + 2 NADH
GTP	Guanosine triphosphate; produced in TCA cycle at succinyl CoA → succinate step; energetically equivalent to ATP
Krebs cycle	Synonym for TCA cycle; named after Hans Krebs
Oxidative decarboxylation	Conversion of pyruvate to acetyl CoA; releases C $O_{2}$ and produces NADH
Oxidative phosphorylation	ATP synthesis via chemiosmosis driven by the ETS proton gradient
Oxaloacetate (OAA)	4-carbon compound that condenses with acetyl CoA to start the TCA cycle; regenerated each turn
Phosphofructokinase (PFK)	Rate-limiting enzyme of glycolysis; allosterically regulated by ATP and AMP
Proton motive force	Electrochemical gradient of $H^{+}$ across the inner mitochondrial membrane that drives ATP synthesis
Pyruvate	3-carbon end product of glycolysis; enters mitochondria under aerobic conditions
Pyruvate dehydrogenase complex	Multi-enzyme complex (requires TPP, N $AD^{+}$ , CoA) that converts pyruvate to acetyl CoA
Respiratory Quotient (RQ)	Ratio of C $O_{2}$ evolved to $O_{2}$ consumed; indicates the respiratory substrate
Substrate-level phosphorylation	Direct ATP synthesis from substrate → ADP + Pi (no ETS); occurs in glycolysis and TCA cycle
TCA cycle	Tricarboxylic acid cycle; 8-step cyclic pathway in mitochondrial matrix; produces NADH, $FADH_{2}$ , GTP, C $O_{2}$
TPP	Thiamine pyrophosphate; cofactor of pyruvate dehydrogenase and α-ketoglutarate dehydrogenase
Ubiquinone (CoQ)	Lipid-soluble mobile electron carrier between Complexes I/II and Complex III in the ETS