Pyruvate Oxidation Krebs Cycle 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: What was produced: • 1 Glucose • • • 2 ATP • 2 NAD+ • 4 ADP • 4 Pi 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 CO 2 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 (Co. A) is attached to the carbon compound, forming acetyl-Co. A 2 pyruvate + 2 NAD+ + 2 Co. A 2 acetyl-Co. A + 2 NADH + 2 CO 2

Overall The two molecules of acetyl-Co. A enter the Krebs cycle The two molecules of NADH proceed to step 4 to participate in oxidative phosphorylation The two CO 2 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 FADH 2 2 ATP 4 CO 2