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inhibited by NADH and acetyl-CoA

• from pyruvate by the pyruvate dehydrogenase complex
• fatty acid oxidation (β-oxidation)
• amino acid catabolism - from ketogenic amino acids
• ketones - usually acetyl-CoA produces ketones but reverse reaction can occur
• alcohol - can be converted to acetyl-CoA

• citrate synthase
• inhibited by ATP, NADH, succinyl-CoA, citrate
• activated by ADP

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• isomerization
• aconitase

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• rate limiting step of citric acid cycle
• isocitrate dehydrogenase
• inhibited by ATP, NADH
• activated by ADP, NAD⁺

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• α-ketoglutarate dehydrogenase complex
• inhibited by ATP, NADH, succinyl-CoA

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• succinyl-CoA synthetase
• The GTP produced in this reaction then phosphorylates an ADP to ATP; this is the only time in the citric acid cycle that ATP is directly produced

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• only step that doesn't occur in mitochondrial matrix
• occurs on inner membrane
• succinate dehydrogenase (also part of electron transport chain)
• the FADH₂ passes the electrons into the electron transport chain

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• fumarase

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• malate dehydrogenase

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• 12.5 ATP per pyruvate
• 32 ATP per glucose

• Complex I (NADH-CoQ oxidoreductase) - uses an iron-sulfur cluster to transfer electrons from NADH to flavin mononucelotide (FMN), and then to coenzyme Q (CoQ), forming CoQH₂. Four protons are translocated
• Complex II (Succinate-CoQ oxidoreductase) - uses an iron-sulfur cluster to transfer electrons from succinate to FAD, and then to CoQ, forming CoQH₂. No proton pumping occurs
• Complex III (CoQH₂-cytochrome c oxidoreductase - uses an iron-sulfur cluster to transfer electrons from CoQH₂ to heme, foming cytochrome c as part of the Q cycle. Four protons are translocated
• Complex IV (cytochromic c oxidase) - uses cytochromes and Cu²⁺ to transfer electrons in the form of hydride ions from cytochrome c to oxygen forming water. Two protons are translocated

It uses one of two shuttle mechanisms to transfer electrons

• Glycerol 3-phosphate shuttle - electrons are transferred from NADH to dihydroxyacetone phosphate (DHAP), forming glycerol 3-phosphate. These electrons can then be transferred to mitochondrial FAD, forming FADH₂
• Malate-aspartate shuttle - electrons are transferred from NADH to oxaloacetate, forming malate. Malate can then cross the inner mitochondrial membrane and transfer electrons to mitochondrial NAD⁺ forming NADH

• lacking oxygen - oxidative phosphorylation won't occur which will cause a buildup of NADH and FADH₂ which will inhibiti the citric acid cycle
• adequate O₂ - rate of oxidative phosphorylation is dependent on availability of ADP