Lecture Sept 17 – Metabolism: Glycolysis, TCA Cycle, ETC, and Cori Cycle (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and concepts from glycolysis, the TCA cycle, the electron transport chain, and the Cori/gluconeogenesis pathways.

Glycolysis

10-step anaerobic pathway in the cytoplasm that converts glucose to two pyruvate molecules, yielding net 2 ATP and 2 NADH per glucose.

Anaerobic metabolism

Metabolic processes that occur without oxygen, such as glycolysis with lactate production.

Aerobic metabolism

Metabolic processes that require oxygen, enabling the mitochondria to fully oxidize pyruvate via the TCA cycle and ETC.

Glucose

Monosaccharide substrate for glycolysis; the starting molecule for energy production.

Glucose-6-phosphate

Glucose phosphorylated by hexokinase; an early glycolytic intermediate and a junction with glycogen metabolism.

Hexokinase

Enzyme that phosphorylates glucose to glucose-6-phosphate.

Fructose-6-phosphate

Glycolytic intermediate formed from glucose-6-phosphate prior to PFK action.

Phosphofructokinase (PFK)

Rate-limiting glycolytic enzyme that converts fructose-6-phosphate to fructose-1,6-bisphosphate.

Fructose-1,6-bisphosphate

Highly active glycolytic intermediate formed by PFK; cleaved to two three-carbon sugars.

Aldolase

Glycolytic enzyme that splits fructose-1,6-bisphosphate into two triose phosphates.

Dihydroxyacetone phosphate

Triose phosphate interconvertible with glyceraldehyde-3-phosphate; both feed into glycolysis.

Glyceraldehyde-3-phosphate

Glycolytic triose phosphate that is oxidized to 1,3-bisphosphoglycerate with NAD+ reduction.

1,3-bisphosphoglycerate

Glycolytic intermediate that donates a phosphate to ADP to form ATP.

Glyceraldehyde-3-phosphate dehydrogenase

Enzyme that oxidizes glyceraldehyde-3-phosphate and reduces NAD+ to NADH.

Phosphoglycerate kinase

Glycolytic enzyme that forms ATP from ADP and 1,3-bisphosphoglycerate.

Phosphoglyceromutase

Enzyme that rearranges 3-phosphoglycerate to 2-phosphoglycerate in glycolysis.

Enolase

Glycolytic enzyme that converts 2-phosphoglycerate to phosphoenolpyruvate.

Phosphoenolpyruvate (PEP)

High-energy glycolytic intermediate that donates phosphate to ADP to form ATP.

Pyruvate

End product of glycolysis; can be reduced to lactate anaerobically or oxidized to acetyl-CoA aerobically.

Pyruvate kinase

Glycolytic enzyme that converts phosphoenolpyruvate to pyruvate with ATP production.

Lactate

Reduced form of pyruvate produced under anaerobic conditions; can be recycled in the Cori cycle.

Lactate dehydrogenase

Enzyme that converts pyruvate to lactate while oxidizing NADH to NAD+.

NAD+/NADH

Electron carriers; NAD+ accepts electrons in glycolysis/TCA; NADH carries electrons to the ETC.

FAD/FADH2

Electron carrier reduced in the TCA cycle (and by succinate dehydrogenase) and donated to the ETC.

Pyruvate dehydrogenase

Mitochondrial complex converting pyruvate to acetyl-CoA, releasing CO2 and generating NADH.

Acetyl-CoA

Two-carbon donor that enters the citric acid cycle by combining with oxaloacetate to form citrate.

Citrate synthase

Enzyme that catalyzes the condensation of acetyl-CoA with oxaloacetate to form citrate.

Citric acid cycle (Krebs cycle/TCA)

aerobic cycle oxidizing acetyl-CoA to CO2, generating NADH, FADH2, and GTP/ATP.

Isocitrate dehydrogenase

Rate-limiting TCA enzyme converting isocitrate to α-ketoglutarate with NADH and CO2 released.

α-Ketoglutarate dehydrogenase

TCA enzyme converting α-ketoglutarate to succinyl-CoA with NADH and CO2 released.

Succinate dehydrogenase

TCA enzyme that converts succinate to fumarate and produces FADH2.

Succinate

TCA intermediate oxidized to fumarate in the cycle.

Fumarase

TCA enzyme that hydrates fumarate to malate.

Malate dehydrogenase

TCA enzyme converting malate to oxaloacetate, producing NADH.

Oxaloacetate

Regenerated four-carbon molecule that condenses with acetyl-CoA to begin the cycle.

NADH

Electron carrier produced in glycolysis and TCA that donates electrons to the ETC.

FADH2

Electron carrier produced in the TCA (via succinate dehydrogenase) that donates to the ETC.

Electron Transport Chain (ETC)

Series of membrane proteins that transfer electrons, pump protons, and drive ATP synthesis.

Intermembrane space

Space between inner and outer mitochondrial membranes where protons accumulate.

Mitochondrial matrix

Innermost compartment of the mitochondrion where the TCA cycle occurs.

Inner mitochondrial membrane

Membrane housing the components of the ETC and ATP synthase.

Outer mitochondrial membrane

Outer boundary of the mitochondrion separating it from the cytosol.

ATP synthase

Enzyme that uses the proton gradient to convert ADP and Pi into ATP.

Chemiosmosis

Process by which a proton gradient drives ATP production across membranes.

Gluconeogenesis

Formation of glucose from non-carbohydrate sources, mainly in the liver.

Cori cycle

Metabolic cycle: lactate from active muscle is transported to liver and converted to glucose.

Glycogen

Stored glucose, primarily in liver and muscle, mobilized during glycolysis/gluconeogenesis.

Citric acid cycle yield (per glucose)

Complete oxidation of one glucose yields CO2, NADH, FADH2, and GTP/ATP in the cycle.

Net ATP from complete glucose oxidation

Approximately 30–32 ATP per glucose, depending on shuttle mechanisms for cytosolic NADH.