1. Cellular Respiration Harvesting Chemical Energy
The process of converting organic “sugar” (potential) energy into a more usable form ATP.

2. Principles of Energy Harvest
Catabolic pathway
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat)
2 pathways:
Fermentation (Anaerobic)
Without O2
Less efficient at producing ATP.
By products:
alcohol, or lactic acid
Cellular Respiration (Aerobic)
With O2
Most prevalent and efficient process for producing ATP

3. Where in the world is …..??? Mitochondria of eukaryotes.
Cytoplasm of prokaryotes.

4. Negative Feedback When ATP concentration down, respiration speeds up.
When ATP concentration up, respiration slows down.

5. Redox reactions Oxidation-reduction LEO GER
OIL RIG (adding e- reduces + charge)
Oxidation is e- loss
Reduction is e- gain
Reducing agent: e- donor
Oxidizing agent: e- acceptor

6. Oxidizing agent in respiration
NAD+ (nicotinamide adenine dinucleotide)
Removes electrons from food
NAD+ is reduced to NADH
Enzyme action: dehydrogenase
Oxygen is the eventual e- acceptor

7. Electron transport chains
Electron carrier molecules (membrane proteins)
Electron route:
Food  NADH  ETC  O2
Chemiosmosis: energy coupling mechanism
Shuttles electrons that release energy creating a proton gradient used to make ATP

8. Cellular respiration Glycolysis: degrades glucose into pyruvate
In cytosol
Kreb’s Cycle: pyruvate into carbon dioxide
In mitochondrial matrix
Electron Transport Chain: electrons passed to oxygen
In inner membrane of mitochondrion

9. Glycolysis 1 Glucose ---> 2 pyruvate molecules
Energy investment phase:
cell uses ATP as fuel
Energy payoff phase:
ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by food oxidation
Net energy yield per glucose molecule:
2 ATP plus 2 NADH
no CO2 is released
occurs aerobically or anaerobically

10. The Transition Reaction
In the presence of oxygen, the two pyruvate molecules produced by glycolysis travel to mitochondria
Pyruvate is converted into acetyl CoA by removing CO2.
NAD+ is converted into NADH.
Coenzyme A (from B vitamin), attaches to the remaining 2-C (acetyl) unit, forming acetyl Co-A.

11. Kreb’s Cycle (citric acid cycle)
Occurs in mitochondrial matrix
Krebs Cycle has 8 steps, each step is catalyzed by a different enzyme
Each cycling requires the input of 2-carbon acetyl-CoA and two carbons are released as C02
4-C Oxaloacetate is regenerated (the “cycle”)
For each pyruvate that enters:
3 NAD+ reduced to NADH
1 FAD+ reduced to FADH2
1 ATP molecule
Each are used in the electron transport system to create large amounts of ATP

12. Electron transport chain
Electron transport chain
Cytochromes carry e-’s from carrier molecules (NADH & FADH2) down to oxygen
Produces H+ gradient pumped into the inner membrane space from E of passing e-’s
ATP synthase:
Enzyme harnesses E from the flow of H+ back into the matrix to phosphorylate ADP to ATP (oxidative phosphorylation)

13. NET RESULTS: Aerobic Respiration
Glycolysis: 2 ATP
Kreb’s Cycle: 2 ATP (substrate-level phosphorylation)
Electron transport & oxidative phosphorylation:
1 NADH = 3ATP
1 FADH2 = 2ATP
Totals:
2 NADH (glycolysis) = 6ATP
2 NADH (acetyl CoA) = 6ATP
6 NADH (Kreb’s) = 18 ATP
2 FADH2 (Kreb’s) = 4 ATP
38 TOTAL ATP/glucose
2 ATP used to move NADH to the mitochondria
grand total of 36 ATP/glucose

14. Related metabolic processes
Fermentation:
Anaerobic conditions (O2 Absent)
Occurs solely in cytoplasm
alcohol~ pyruvate to ethanol (yeast)
lactic acid~ pyruvate to lactate (humans)
Facultative anaerobes
Can carry out metabolism in the presence or absence of O2 (Humans)
Beta-oxidation lipid catabolism