Stage 3: Kreb’s Cycle

Kreb’s Cycle 8 step process Each step is catalyzed by a specific enzyme It is a cyclic process because you start and end with oxaloacetate

1 8 2 3 7 CoA 6 +Pi 4 5

GDP + Pi GTP ATP ADP

Overall Equation Oxaloacetate + acetyl CoA + ADP + Pi + 3NAD+ + FAD +H2O CoA + ATP + 3NADH + FADH2 + 2CO2 + oxaloacetate TIMES TWO!!!!

By the end of this cycle, the original molecule is entirely consumed The 6 carbon atoms leave the process as CO2 All that is preserved of the original glucose molecule is most of its energy, which is stored in the form of: 4 ATP (2 from glycolysis and 2 from Kreb’s) 10 NADH (2 from glycolysis, 2 from pyruvate oxidation, 6 from Kreb’s) 2 FADH2 (from Kreb’s) Most of the energy stored in NADH and FADH2 will eventually be transferred to ATP in the last stage of respiration

Homework Section 4.2 p.175-177 Complete questions