BI7.1-2 | Integration of Metabolism and Biological Oxidation — Glossary

The activated two-carbon unit that serves as the central metabolic intermediate linking carbohydrate, lipid, and protein metabolism to the TCA cycle

The first metabolic crossroads after glucose enters a cell; can enter glycolysis, glycogenesis, pentose phosphate pathway, or be dephosphorylated to free glucose (liver/kidney only)

The tricarboxylic acid (Krebs) cycle in the mitochondrial matrix that oxidises Acetyl-CoA, generating 3 NADH, 1 FADH2, and 1 GTP per turn

Four protein complexes (I-IV) in the inner mitochondrial membrane that transfer electrons from NADH/FADH2 to oxygen, pumping protons to create an electrochemical gradient

ATP synthesis driven by the proton-motive force generated by the electron transport chain; produces the majority of cellular ATP

Peter Mitchell's Nobel Prize-winning hypothesis (1978) that the proton gradient across the inner mitochondrial membrane (proton-motive force) drives ATP synthesis by ATP synthase

The electrochemical gradient of protons across the inner mitochondrial membrane, comprising an electrical component (delta-psi, ~150-180 mV) and a chemical component (delta-pH); total ~200 mV

Complex V — the molecular rotary motor with F0 (proton channel) and F1 (catalytic head) subunits that synthesises ATP from ADP + Pi using proton flow down the gradient

The number of ATP molecules synthesised per oxygen atom consumed; approximately 2.5 for NADH and 1.5 for FADH2 (revised values)

Dissipation of the proton gradient without ATP synthesis, generating heat instead; mediated physiologically by UCP1 (thermogenin) in brown adipose tissue

A mobile lipid-soluble electron carrier in the inner mitochondrial membrane that collects electrons from Complex I, II, and other dehydrogenases and delivers them to Complex III

A small water-soluble haem protein in the intermembrane space that shuttles electrons from Complex III to Complex IV

The synthesis of glucose from non-carbohydrate precursors (lactate, alanine, glycerol) primarily in the liver during fasting; requires glucose-6-phosphatase for glucose export

The synthesis of ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) from excess Acetyl-CoA in liver mitochondria during fasting and starvation

The anabolic hormone of the fed state that promotes glucose uptake (GLUT4), glycogenesis, lipogenesis, and protein synthesis

The catabolic hormone of fasting that promotes glycogenolysis, gluconeogenesis, lipolysis, and ketogenesis via cAMP-PKA signalling

The metabolic cycle where lactate from anaerobic glycolysis in muscle is transported to liver for gluconeogenesis back to glucose

The metabolic state (0-4 hours post-meal) dominated by high insulin:glucagon ratio, characterised by storage and biosynthesis

Prolonged fasting (days to weeks) where the brain adapts to using ketone bodies, reducing glucose requirement from 120 g/day to ~40 g/day

A life-threatening metabolic emergency in type 1 diabetes caused by absolute insulin deficiency leading to uncontrolled lipolysis, massive ketogenesis, and metabolic acidosis

A potentially fatal complication when malnourished patients are fed too quickly; sudden insulin surge drives phosphate, potassium, and magnesium into cells, causing cardiac arrhythmias

Paul Boyer's model (Nobel Prize 1997) where ATP synthase beta-subunits cycle through O (open), L (loose), and T (tight) conformations driven by gamma-shaft rotation

The elegant mechanism at Complex III that maximises proton pumping by oxidising QH2 at the Qo site and regenerating QH2 at the Qi site, pumping 4 H+ per electron pair

Specialised fat tissue containing UCP1 (thermogenin) that generates heat by uncoupling oxidative phosphorylation; important for neonatal thermogenesis

An antibiotic that inhibits ATP synthase by blocking the proton channel in the F0 subunit, preventing proton flow and stopping ATP synthesis