1. Harvesting Chemical Energy
Cellular Respiration
Harvesting Chemical Energy

2. Metabolism All organisms have metabolic pathways
Each step of the pathway is controlled by different enzymes
Eukaryotic organelles compartmentalize pathways

3. Glucose Most organisms use glucose (C6H12O6) as a source of energy
Cells oxidize glucose for energy
Energy is typically captured as ATP
Can involve as many as 3 pathways: Glycolysis, Cellular Respiration, Chemiosmosis
Aerobic produces 38 ATP; anaerobic 2

4. Oxidation/Reduction Reactions
The gain of electrons or hydrogen atoms is called reduction
The loss of electrons or hydrogen atoms is called oxidation
Oxidation and reduction reactions are always coupled

5. NAD (nicotinamide adenine dinucleotide)
May exist as NAD+ (oxidized) or NADH(reduced)
The oxidation of NADH produces energy

6. Glycolysis Occurs in the cytoplasm of the cell Anaerobic
Produces two molecules of pyruvate, two ATP, and two NADH
Some steps are endergonic (require energy)

7. Glycolysis Diagram

8. Key Points of Glycolysis
Begins with a 6-C sugar that is converted into two 3-C sugars
Produces two G3P (glyceraldehyde 3-phosphate) molecules
ATP is used as a source for phosphate groups and energy
Energy producing steps occur when phosphate groups are transferred to ADP from ATP and NAD+ is reduced
ATP is produced by substrate level phosphorolation
Two ATPs are used and 4 are produced with a net gain of two ATPs

9. Acetyl COA Production Occurs on the inner mitochondrial membrane
CO2 is liberated and NADH+H and Acetyl COA is produced

10. Diagram of acetyl COA production

11. Citric Acid Cycle Consists of eight reactions
Majority takes place in the mitochondrial matrix
Each time CO2 is released NAD is reduced
Each cycle produces: two CO2 molecules, Reduces three NAD, One FADH2 , and one ATP

12. Diagram of the Citric acid Cycle

13. Electron Transport Chain
Involves the passing of electrons through a series of membrane associated electron carriers in the mitochondria to produce ATP
The respiratory chain is composed of enzymes that shuttle electrons from NADH and FADH2 across the membrane
Creates a proton gradient
Oxygen is final electron acceptor

14. ATP production from gradient
An ATP synthase in the inner mitochondrial membrane makes ATP
ATP must be removed from mitochondrial matrix so proton gradient is in favor of ATP synthesis
If proton flow is uncoupled from ATP synthase, energy is lost as heat

16. Fermentation Occurs in cell cytoplasm
Reduces pyruvate and return NAD for use in glycolysis in the absence of oxygen
Allows cell to produce small amounts of ATP
Two types: lactic acid fermentation and alcoholic fermentation

17. Energy yields
Aerobic yields 36 ATP
Anaerobic yields 2 ATP