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 P i 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 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 (CoA) is attached to the carbon compound, forming acetyl-CoA 2 pyruvate + 2 NAD CoA 2 acetyl-CoA + 2 NADH + 2 CO 2

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 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 FADH2 2 ATP 4 CO 2