1. 5.6 ETS

2. 5.6 Electron Transport System
General Summary
NADH & FADH2 from glycolysis & Krebs cycle carry H atoms (p+ & e-) to the ETS;
Reduce oxygen to form water and synthesize ATP.
ETS consists of enzymes & cytochromes (other proteins) embedded in the inner mitochondrial membrane.

3. 5.6 Electron Transport System
e- (from NADH & FADH2 are transferred step by step through an ETS by cytochromes.
At each transfer, some energy is released.
Some of this energy is used to actively transport H+ out of the matrix into the intermembrane space.

4. 5.6 Electron Transport System
Some H+ will diffuse back into the matrix through ATP synthase.
The H+ transfers some energy to the ATPsynthase, which then synthesizes ATP from ADP & P.
The final cytochrome (e- acceptor) is an enzyme that combines the e- & H+ with O2 to form water.

5. 5.6 Electron Transport System
The H from NADH provides enough energy to synthesize 3 ATP molecules.
The H from FADH2 only has enough energy to synthesize 2 ATP molecules.

6. 5.6 Electron Transport System
ETS Animation

7. 5.6 Electron Transport System
Bacteria don’t have mitochondria.
Their ETS is in their cell membranes.
In some, O2 isn’t the final e- acceptor - depending on the e- acceptor, they can produce H2S or NH3. (anaerobic respiration).

8. 5.6 Electron Transport System
Facultative anaerobes – can survive with or without O2, and can switch between fermentation & aerobic respiration
Obligate anaerobes – cannot survive with O2, so can only perform fermentation or anaerobic respiration
Obligate aerobes – cannot survive long without O2

9. 5.7 Oxygen, Respiration, & Photosynthesis
Without O2, cells must perform fermentation - only releases 2 ATP per glucose.
As long as O2 is present, we gain more energy from our food.
Humans (& other animals) get their O2 from breathing in air, which comes from photosynthesis.

10. 5.7 Oxygen, Respiration, & Photosynthesis

11. Relating Photosynthesis & Cellular Respiration
6 CO2 + 6 H2O → C6H12O6 + 6 O2
Cellular Respiration:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
The products of photosynthesis are the raw materials for cell respiration & the products of cell respiration are the raw materials for photosynthesis.
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12. Relating Photosynthesis & Cellular Respiration
6 CO2 + 6 H2O → C6H12O6 + 6 O2
Cellular Respiration:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
Both processes provide carbon skeletons used in biosynthesis & use an ETS to form ATP, but they differ in their energy source.
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13. Relating Photosynthesis & Cellular Respiration
Respiration: Releases chemical energy by reducing oxygen to water & oxidizing sugars to carbon dioxide.
Photosynthesis: Stores chemical energy by oxidizing water to oxygen & reducing carbon dioxide to sugar.