1. Cellular Respiration Part 3
Krebs Cycle – Pages 96 to 97

2. Chemically Grooming Pyruvate
3 steps to Krebs Cycle
Carbon atom is removed (3C to 2C) and released as CO2
2C compound is oxidized while NAD+ is reduced to NADH
Coenzyme A joins with 2C to form acetyl co-A

3. CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 3 Acetyl CoA Pyruvate
Fig. 9-10
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+ 2 1 3
Acetyl CoA
Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the citric acid cycle
Pyruvate
Coenzyme A
CO2
Transport protein

4. Krebs Cycle (Citric Acid Cycle)
Called the Citric Acid Cycle because Citric Acid (citrate) is the 1st molecule formed in the cycle
Called the Krebs Cycle after Hans Krebs – the researcher who discovered it
Occurs in the matrix of the mitochondria
Involves 2 electron carriers – NADH and FADH2
The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn

5. Pyruvate CO2 NAD+ CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle 2
Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle 2
CO2
Figure 9.11 An overview of the citric acid cycle
FADH2
3 NAD+
FAD 3
NADH
+ 3 H+
ADP + P i
ATP

6. Summary of Krebs Cycle
2C of acetyl Co-A joins with 4C of OAA to form 6C citrate; Co-A is recycle
Thru a series of energy extracting reactions 2CO2, 3NADH, 1FADH2 + 1 ATP are produced per turn
Remaining 4C molecule is rearranged to form OAA

7. Products for 1 glucose including grooming:
Fig
Acetyl CoA
Products for 1 glucose including grooming:
8 NADH
2 FADH2
2 ATP
6 CO2
Products for 1 turn including grooming:
4 NADH
1 FADH2
1 ATP
3 CO2
CoA—SH
NADH
+H+ 1
H2O
NAD+ 8
Oxaloacetate 2
Malate
Citrate
Isocitrate
NAD+
Citric
acid
cycle
NADH 3 7
+ H+
H2O
CO2
Fumarate
CoA—SH
-Keto-
glutarate
Figure 9.12 A closer look at the citric acid cycle 4 6
CoA—SH
FADH2 5
CO2
NAD+
FAD
Succinate P
NADH i
GTP
GDP
Succinyl
CoA
+ H+
ADP
ATP