This document summarizes the citric acid cycle, also known as the Krebs cycle or TCA cycle. It outlines the key steps in the cycle, including the enzymes involved in each reaction. These steps ultimately generate ATP through oxidative phosphorylation as acetyl-CoA is oxidized, yielding carbon dioxide and hydrogen ions. In total, the oxidation of one acetyl-CoA molecule in the TCA cycle produces 10 ATP molecules. The TCA cycle is also regulated and provides intermediates for other biosynthetic processes.

2. Citric Acid Cycle

3. Gylcolysis
Electron Transport and
Oxidative phosphorylation
TCA Cycle

5. Entry into the TCA Cycle

8. 
Only step in TCA cycle that involves the
formation of a C-C bond

13. Isocitrate Dehydrogenase

15.  -Ketoglutarate Dehydrogenase

17. Succinyl-CoA Synthetase

20. Fumarase

22. Malate Dehydrogenase

24. 
Acetyl-CoA + 3 NAD+ + Q + GDP + Pi +2 H20  HSCoA + 3NADH + QH2 + GTP + 2 CO2 + 2 H+

Isocitrate Dehydrogenase
1 NADH=2.5 ATP

a-ketoglutarate dehydrogenase
ATP
1 NADH=2.5

Succinyl-CoA synthetase
1 GTP=1 ATP

Sunccinate dehydrogenase

Malate Dehydrogenase
ATP

Total of 10 ATPs gained from oxidation of 1 Acetyl-CoA
1 QH2=1.5 ATP
1 NADH=2.5

26. Regulation of
TCA Cycle

29. Protein/amino acid
Catabolites feed
Into the TCA Cycle

30. Fats breakdown and feed
into the TCA Cycle

31. TCA Cycle provides intermediates
for many biosynthetic processes

32. The "filling up" reactions
• PEP carboxylase - converts PEP to oxaloacetate
• Pyruvate carboxylase - converts pyruvate to oxaloacetate
• Malic enzyme converts pyruvate into malate

34. Following the carbons
through the TCA cycle