1. The Krebs Cycle Biology 11 Advanced

2. The Beginning Three major stages of cellular respiration:
1. Glycolysis (splitting of sugar)
2. The Citric Acid Cycle
3. Oxidative Phosphorylation (production of ATP): Electron Transport and Chemiosmosis.
Glycolysis, which occurs in the cytosol, begins the degradation process by breaking down glucose into two molecules of a compound called pyruvate.
The citric acid cycle, which takes place in the mitochondrial matrix, completes the breakdown of glucose by oxidizing a derivative of pyruvate to carbon dioxide.
In the third stage, the electron transport chain accepts electrons from the breakdown products of the first two stages and passes these electrons from one molecule to the other.
The energy released at each step of the chain is stored in a form the mitochondrion can use to make ATP.

4. Cellular Respiration theoretically produces 38 molecules of ATP

5. Stage 1 - Glycolysis
Glucose, a six carbon sugar, is split into two three carbon sugars. These smaller sugars are then oxidized and their remaining atoms rearranged to form two molecules of pyruvate (pyruvate is the ionized form of pyruvic acid.)
You need to know that during glycolysis, a glucose molecule is broken down into two pyruvate, or pyruvic acid, molecules and 2 ATP are formed.

6. Stage 2 - The Krebs Cycle
Also known as the Citric Acid Cycle/Tricarboxylic Acid Cycle
What is it? It is a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration.
Upon entering the mitochondrion via active transport, pyruvate is first converted to a compound called acetyl coenzyme A, or acetyl CoA.

7. 8 Steps of the CAC
Acetyl CoA adds its two-carbon acetyl group to oxaloacetate, producing citrate.
Citrate is converted to its isomer by the removal of one water molecule and addition of another.
Citrate loses a CO2 molecule, and the resulting compound is oxidized, reducing NAD+ to NADH.
4. Another CO2 is lost, and the resulting compound is oxidized, reducing NAD+ to NADH. The remaining molecule is then attached to coenzyme A by an unstable bond.

8. 5. CoA is displaced by a phosphate group which is transferred to GDP, for GTP, and then to ADP, forming ATP.
6. Two hydrogens are transferred to FAD, forming FADH2 and oxidizing succinate.
7. Addition of a water molecule rearranges bonds in the substrate.
8. The substrate is oxidized, reducing NAD+ to NADH and regenerating oxaloacetate.