1. Cellular Respiration Continued
Chapter 9

2. The Krebs Cycle
Series of enzyme-controlled reactions which release energy from the 2 pyruvate molecules that were formed by glycolysis.
Occurs in the mitochondrial matrix; CO2 is produced; yields 2 ATP (per glucose).
Pyruvate (3-C) molecules move from the cytosol into the mitochondrion by a carrier protein in the mitochondrial membrane.
Now the Krebs Cycle (or the Citric Acid Cycle) (or the Tricarboxylic Acid Cycle) will begin.

4. Hans Krebs rocks!
Two turns of the Krebs Cycle produces two ATPs from 1 glucose.
Also produces 6 NADH and 2 FADH2 with many high energy electrons.

5. Electron Transport Chain
Only 4 molecules of ATP are produced by substrate-level phosphorylation:
Most molecules of ATP are produced by oxidative phosphorylation in the ETC.
At the end of the Krebs Cycle, most of the energy extracted from glucose is in molecules of NADH and FADH2.
The transfer of electrons down the ETC to oxygen leads to ATP synthesis.
The electron transport chain is made of electron carrier molecules embedded in the inner mitochondrial membrane.

6. ETC cont.
The electron transport chain does not make ATP directly. It generates a proton gradient across the inner mitochondrial membrane, which stores potential energy that can be used to phosphorylate ADP.
H+ ions are pumped across the inner membrane as e- are transferred.
H+ will then diffuse back through via ATP synthase membrane protein.
Chemiosmosis - The coupling of ion flow across a membrane to drive cellular work, like ATP production.

8. Oxidative Phosphorylation
The build-up of H+ on one side of the inner membrane sets up a proton gradient, a source of potential energy.
At least 6 protons are moved across per NADH/FADH2.
H+ will pass back through ATP synthase where ADP is phosphorylated to ATP.
1 NADH makes approx 3 ATP; 1 FADH2 makes approx 2 ATP.

9. Animations

10. Anaerobic Pathways (Fungi, bacteria) Alcoholic fermentation:
Pyruvate + NADH  ethanol + CO2 + 2 ATP.
(Fungi, bacteria, muscle cells) Lactic acid fermentation:
Pyruvate + NADH  lactic acid + 2 ATP.
Lactic acid accumulation results in burning, painful muscles; lactic acid can be converted back to pyruvate when oxygen levels rise again, or blood can carry it to the liver for processing.

12. SONGS…