Pyruvate Oxidation and the Krebs Cycle

Vocabulary terms covering cellular respiration, specifically focusing on Pyruvate Oxidation and the Krebs Cycle, including redox reactions, enzymatic precursors, and energy-rich products.

Oxidation

The loss of one or more electrons ($e^-$) and/or Hydrogen atoms ($H$) from a substance that reduces its energy content.

Reduction

The gain of one or more electrons ($e^-$) and/or $H$ atoms by a substance that increases its energy content.

Redox Reactions

Oxidation and reduction reactions used by cells to release and transfer energy from food molecules.

Mitochondrion Matrix

The location within the mitochondrion where Pyruvate Oxidation and the Krebs Cycle occur.

Aerobic Conditions

Conditions in which Oxygen ($O_2$) is present, required for most ATP production in the mitochondrion.

Pyruvate Oxidation

The process that catabolizes pyruvate produced during glycolysis into energy-rich Acetyl CoA and NADH molecules, while releasing one molecule of $CO_2$.

Acetyl Coenzyme A (Acetyl CoA)

An energy-rich 2-C molecule produced by pyruvate oxidation that feeds into the citric acid cycle.

Krebs Cycle

Also called the Citric Acid Cycle; a sequence of eight enzymatic reactions that release energy from Acetyl CoA to produce FADH2, GTP, NADH, and two $CO_2$ molecules.

Citrate

A 6-carbon compound produced in the Krebs cycle when a 2-carbon acetyl group combines with 4-carbon oxaloacetate.

Oxaloacetate

A 4-carbon molecule that combines with Acetyl-CoA to form citrate and is regenerated at the end of the Krebs cycle.

Vitamin B1 (Thiamine)

A precursor to the essential coenzyme Thiamine Pyrophosphate (TPP) used in pyruvate oxidation.

Vitamin B2 (Riboflavin)

A precursor used to make the essential coenzyme FAD.

Vitamin B3 (Niacin)

A precursor used to make the essential coenzyme $NAD^+$.

Vitamin B5 (Pantothenic Acid)

A precursor used to make Coenzyme A (CoA).

GTP

An energy-rich molecule produced by the Krebs cycle from GDP; it can be converted to ATP.

FADH2

An energy-rich molecule produced from FAD that supplies energy-rich electrons ($e^-$) to the electron transport chain.

NADH

An energy-rich molecule produced from $NAD^+$ that donates electrons to the electron transport chain to energize ATP synthase.

Nucleoside-Diphosphate Kinase

The enzyme responsible for converting 1 GTP molecule to 1 ATP molecule.

Carbon Dioxide ($CO_2$)

A catabolic waste product produced during pyruvate oxidation (1 molecule) and the Krebs cycle (2 molecules) that is removed via exhalation.

Amphibolic

A term describing the Krebs cycle because it involves both anabolic processes (making amino acids, lipids, etc.) and catabolic processes.

NADH to ATP Yield

One NADH molecule is used to make approximately $2.5 - 3$ ATP molecules.

FADH2 to ATP Yield

One FADH2 molecule is used to make approximately $1.5 - 2$ ATP molecules.