1. Matrix Reactions
The Fun Begins

2. The Mitochondria
Since all the reactions after glycolysis occur in the mitochondria let’s review its structure
The Matrix is the fluid filled (Jelly like consistency) space that is located inside the inner membrane
The Inner membrane are all the folds that have a large surface area
The name for the folds are called Cristae and the more folds the larger the surface area

3. Pyruvate Oxidation: Preparing for Krebs
For each step remember it is X2 as there are 2 pyruvate molecules
The pyruvate molecule moves from the cytosol to the matrix of the mitochondria
Once the pyruvate enters the matrix a carboxyl group is removed forming CO2
In a second step the acetyl group is oxidized and NAD+ is reduced forming NADH + H+
In the third step a molecule called coenzyme A is added to the acetyl group forming acetyl-CoA
Steps 1-3 are simultaneous and take place on the pyruvate dehydrogenase complex

4. Pyruvate Oxidation: In Pictures

5. Krebs’ Cycle: Now the Fun Begins1 2 3 4 5 6 7 8
The Cycle occurs in 8 steps.

6. Krebs’ Cycle: Step 1 1 2 3 4 5 6 7 8
The acetyl Co-A enters the Krebs’ Cycle by bonding to Oxaloacetate via a dehydration synthesis reaction
This forms a 6 carbon molecule called citrate and coenzyme-A (Co-A) is released
At the end of one turn of the Krebs’ Cycle oxaloacetate will be recycled

7. Krebs’ Cycle: Step 2 1 2 3 4 5 6 7 8
Citrate is transformed to Isocitrate via a two step process

8. Krebs’ Cycle: Step 3 Isocitrate loses a carboxyl group
It is also oxidized (loses 2 electrons) by the removal of a hydrogen molecule
This process is called oxidative decarboxylation
The products are CO2, NADH/ H+ and
a-Ketoglutarate 1 2 3 4 5 6 7 8

9. Krebs’ Cycle: Step 4 1 2 3 4 5 6 7 8
a-ketoglutarate also undergoes oxidative decarboxylation and loses a carboxyl group and is oxidized
NADH, H+ and CO2 are produced
At the same time Coenzyme- A is attached to the new 4 carbon molecule
End result is Succinyl-CoA

10. Krebs’ Cycle: Step 5 1 2 3 4 5 6 7 8
Succinyl CoA loses its CoA which fuels substrate level phosphorylation
This means a GTP is made
GTP is a high energy molecule like ATP and it will give his phosphate up to ADP to make ATP
The products of this step are Coenzyme A, ATP and Succinate

11. Krebs’ Cycle: Step 6 1 2 3 4 5 6 7 8
Succinate is oxidized (by removing two hydrogen atoms) and FAD is reduced forming FADH2
The resulting molecule is FUMARATE

12. Krebs’ Cycle: Step 7 Fumarate is hydrated forming Malate 1 2 3 4 5 6 78
Fumarate is hydrated forming Malate

13. Krebs’ Cycle: Step 8 1 2 3 4 5 6 7 8
Malte is oxidized and NAD+ is reduced (2 hydrogen atoms come off again)
The products of this stage are NADH, H+ and OXALOACETATE

14. Krebs’ Cycle Summary 4 CO2 + 6 NADH + 2 ATP + 2 FADH2
Net Result for 1 turn of the Krebs’ Cycle is : (2 CO2, 3 NADH, ATP and FADH2) x 2 (2 pyruvate per glucose) Grand Total is:
4 CO NADH ATP FADH2

15. Matrix Reaction Summary
At the end of the matrix reactions for both pyruvate molecules you end up with:
6 CO NADH ATP FADH2