Download Step 2: Pyruvate Oxidation

Pyruvate Oxidation & Krebs Cycle
STEP 2: PYRUVATE OXIDATION
Recall…
Recall Step 1 - Glycolysis
• Happens in the cytoplasm
• Does not require oxygen (anaerobic)
• Inefficient (net 2 ATP produced)
Glycolysis Summary
What went in:
• 1 Glucose
• 2ATP
• 2 NAD+
• 4 ADP
• 4 Pi
What was produced:
• 2 pyruvate
• 2 ADP
• 2 NADH + H+
• 4 ATP
Step 2 – Pyruvate Oxidation
Overview
 The two pyruvate molecules formed in
glycolysis are transported through the two
mitochondrial membranes into the matrix
 Within the matrix, enzymes catalyze the
following three changes
 Happens twice for every glucose molecule
Three Steps of Pyruvate Oxidation
1. A carboxyl group is removed as CO2
2. The remaining two-carbon molecule is
oxidized by NAD+. This is a redox reaction –
pyruvate is oxidized, and NAD+ is reduced
3. Coenzyme A (CoA) is attached to the carbon
compound, forming acetyl-CoA
2 pyruvate + 2 NAD+ + 2 CoA
2 acetyl-CoA + 2 NADH + 2 CO2
Overall
 The two molecules of acetyl-CoA enter the Krebs
cycle
 The two molecules of NADH proceed to step 4 to
participate in oxidative phosphorylation
 The two CO2 molecules diffuse out of the cell as
waste
 The two H+ molecules remain dissolved in the
matrix
 No ATP is directly produced in this step
STEP 3: KREBS CYCLE
Overview
• also called the Citric Acid Cycle
• named after the Nobel Prize winner who
discovered it
• Occurs in the mitochondrial matrix
• 8 step process
• Remember that the Krebs Cycle happens
TWICE for every one molecule of glucose.
Overall
The Krebs cycle will produce the following
products for every glucose molecule broken
down
•
•
•
•
6 NADH
2 FADH2
2 ATP
4 CO2