Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules

Flashcards from Concept 9.3 of Pearson's Campbell Biology, Twelfth Edition.

Pyruvate

Molecules created as a product of glycolysis in the first step of cellular respiration to be passed into processes for pyruvate oxidation and the citric acid cycle

Pyruvate oxidation

The removal of electrons from a pyruvate molecule before entering the citric acid cycle with most of the energy from glucose remaining

• Happens within a mitochondrion if oxygen is present, or within the cytosol for aerobic prokaryotes

Coenzyme A

The coenzyme that pyruvate is joined to to form acetyl CoA after pyruvate oxidation

Acetyl coenzyme A (Acetyl CoA)

The substance pyruvate is converted to before entering the citric acid cycle

Pyruvate dehydrogenase

An enzyme that breaks down pyruvate through the catalyzation of three reactions

• Oxidation of pyruvate’s carboxyl group, releasing the first CO₂ of cellular respiration

• Reducation of NAD+ to NADH

• Combination of the remaining two-carbon fragment with coenzyme A to form acetyl CoA

Citric acid cycle (Krebs cycle)

Cycle that oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH₂ per turn as well as 2 CO₂ as waste

• Runs twice per glucose molecule consumed due to 2 pyruvate being present after glycolysis

• Has eight steps, each catalyzed by a specific enzyme, to join acetyl CoA and oxaloacetate to form citrate and then decompose it back to oxaloacetate for a cycle

• NADH and FADH₂ carry electrons to the electron transport chain

Oxaloacetate

The molecule that acetyl CoA is joined with to form citrate and is eventually decomposed back to after the citric acid cycle

Citrate

The molecule that results when joining acetyl CoA and oxaloacetate before decomposing back into oxaloacetate

NADH and FADH₂

The two electron carriers produced by the citric acid cycle to carry electrons to the electron transport chain