Glossary Chp 8

Glossary

Chapter 8 “How Cells Use Energy”

Chapter 8 acetyl-CoA

Coenzyme A attached to a two-carbon fragment from pyruvate, which it transfers to oxaloacetate for the Krebs cycle.

aerobic respiration

Oxygen-requiring pathway of ATP formation; from glycolysis, to Krebs cycle, to electron transfer phosphorylation. Typical net energy yield: 36 ATP per glucose molecule.

alcoholic fermentation

Anaerobic ATP-forming pathway. Pyruvate from glycolysis is degraded to acetaldehyde, which accepts electrons from NADH to form ethanol; NAD+ needed for the reactions is regenerated. Net yield: 2 ATP.

anaerobic electron transfer

Flow of electrons through transfer chains in plasma membrane that drives ATP formation. A compound other than oxygen is the final electron acceptor.

electron transfer phosphorylation

Last stage of ATP formation by aerobic respiration; uses the hydrogen and electrons that many reduced coenzymes deliver to electron transfer chains.

FAD

Flavin adenine dinucleotide, a type of nucleotide coenzyme; it transfers electrons and unbound protons (H+) between reaction sites. At such times it is abbreviated FADH2.

glycolysis

Breakdown of glucose or another organic compound to two pyruvate molecules. First stage of aerobic respiration, fermentation, and anaerobic electron transfer. Oxygen has no role in glycolysis, which occurs in the cytoplasm of all cells. Two NADH form. Net yield: 2 ATP per glucose molecule.

Krebs cycle

A stage of aerobic respiration, in mitochondria only; it (and a few preparatory steps) breaks down pyruvate to CO2 and H2O. Many coenzymes accept protons (H+) and electrons from intermediates and deliver them to the next stage of reactions; 2 ATP form.

lactate fermentation

An anaerobic pathway of ATP formation. Pyruvate from glycolysis is converted to three-carbon lactate, and NAD+ is regenerated. Net energy yield: 2 ATP.

mitochondrion

Double-membrane organelle of ATP formation. Only site of aerobic respiration's second and third stages. May have endosymbiotic origins.

NAD+

A nucleotide coenzyme can pick up and carry electrons and H+ to a reaction site.

oxaloacetate

A fourcarbon compound with roles in metabolism (e.g., the point of entry into the Krebs cycle).

pyruvate

Organic compound with a backbone of three carbon atoms. Two molecules form as end products of glycolysis.

substrate-level phosphorylation

The direct, enzyme-mediated transfer of a phosphate group from a substrate to a molecule, as when an intermediate of glycolysis is made to give up a phosphate group to ADP, forming ATP.