Cellular Energetics – BIOL 3030 Lecture 6

Vocabulary flashcards highlighting essential terms and definitions from the Cellular Energetics lecture, covering glucose metabolism, redox chemistry, respiration pathways, and ATP synthesis mechanisms.

Fuel

A molecule whose stored chemical energy can be released for cellular work; glucose is the most common biological fuel.

Glucose

A six-carbon sugar (C6H12O6) that is the primary fuel oxidized to generate ATP in cells.

ATP (Adenosine Triphosphate)

The cell’s main energy currency; produced from ADP + Pi using energy released by metabolic pathways.

Electron Carrier

Molecule that temporarily holds electrons and energy during redox reactions (e.g., NADH, FADH2).

NAD+ / NADH

Coenzyme that cycles between oxidized (NAD+) and reduced (NADH) states, shuttling electrons to the ETC.

FAD / FADH2

Redox cofactor that carries electrons from the citric acid cycle to the ETC in its reduced form, FADH2.

Redox Reaction

A chemical reaction involving electron transfer; oxidation and reduction always occur together.

Oxidation

Loss of electrons (or hydrogen atoms) from a molecule during a redox reaction.

Reduction

Gain of electrons (or hydrogen atoms) by a molecule during a redox reaction.

Glycolysis

Cytosolic pathway that converts glucose to two pyruvate molecules, producing 2 ATP and 2 NADH without CO2 release.

Substrate-Level Phosphorylation

Formation of ATP by direct transfer of a phosphate group from an organic substrate to ADP (occurs in glycolysis and the citric acid cycle).

Pyruvate

Three-carbon end product of glycolysis; key branch point for aerobic respiration or fermentation.

Pyruvate Oxidation

Mitochondrial process linking glycolysis to the citric acid cycle; converts pyruvate to acetyl CoA, producing NADH and CO2.

Acetyl CoA

Two-carbon molecule attached to coenzyme A; entry substrate for the citric acid cycle.

Citric Acid Cycle (Krebs Cycle)

Mitochondrial matrix pathway that completes glucose oxidation; yields CO2, NADH, FADH2, and GTP/ATP.

Oxaloacetate

Four-carbon compound that reacts with acetyl CoA to start the citric acid cycle and is regenerated each turn.

Electron Transport Chain (ETC)

Series of membrane protein complexes in the inner mitochondrial membrane that transfer electrons to O2 and pump protons.

Oxidative Phosphorylation

Coupled processes of the ETC (electron transport) and ATP synthesis driven by the resulting proton gradient.

Proton Motive Force (PMF)

Electrochemical gradient of protons across a membrane that stores potential energy for ATP production.

ATP Synthase (FoF1 Complex)

Rotary enzyme that uses PMF to catalyze ADP + Pi → ATP as protons flow through its Fo channel.

Chemiosmosis

Mechanism by which ATP synthase harnesses PMF to form ATP.

Cristae

Infoldings of the inner mitochondrial membrane that increase surface area for the ETC and ATP synthase.

Mitochondrial Matrix

Innermost compartment of mitochondria containing enzymes for pyruvate oxidation and the citric acid cycle.

Intermembrane Space

Region between the outer and inner mitochondrial membranes where protons accumulate during electron transport.

CoQ (Ubiquinone)

Lipid-soluble electron carrier that transports electrons from complexes I/II to complex III in the ETC.

Cytochrome c

Small peripheral protein that shuttles electrons between complexes III and IV of the ETC.

Aerobic Respiration

Complete oxidation of glucose in the presence of oxygen, yielding up to ~32 ATP per glucose.

Anaerobic Respiration

Energy-yielding pathway using an ETC with an electron acceptor other than O2 (found in some prokaryotes).

Fermentation

Anaerobic process that reoxidizes NADH to NAD+, producing lactate or ethanol and yielding 2 ATP per glucose.

Proton Gradient

Difference in proton concentration and charge across a membrane, central to energy conversion in cells.

Chemiosmotic Theory

Concept that PMF generated by the ETC drives ATP synthesis via ATP synthase.

Substrate Oxidation

Removal of electrons from metabolic intermediates (e.g., in glycolysis or the citric acid cycle) to form reduced electron carriers.

GTP

Guanosine triphosphate; energy molecule generated in the citric acid cycle that can transfer its phosphate to ADP to form ATP.