1. Electron Transport System & Chemiosmosis
Oxidative Phosphorylation

2. Phases of aerobic cellular respiration
Glycolysis
Transition / Link or Acetyl-CoA reaction
Krebs cycle
Electron transport system
These phases are nothing more than metabolic reactions involving the conversion of glucose & other molecules into carbon dioxide & water
The resulting energy released from this conversion will be used to produce ATP

5. Cellular Respiration: Last Step
Electron transport System (ETS)
Occurs in within the inner mitochondrial membrane
Reactants = 10 NADH, 2 FADH2, 6 O2, ADP + Pi
Products = approximately 36 – 38 ATPs, 4 H2O

6. Electron Transport System
The ETS is a series of electron carriers embedded in the inner membrane of the mitochondrion.
Each electron carrier in the system is slightly more electronegative than the one before it.
Electrons enter ETS from NADH & FADH2
As the electrons are passed from carrier to carrier, they give off energy because they’re being passed to more and more electronegative carriers.

8. Electron Transport System
That energy given off by the electrons as they travel is used to pump H+ from the matrix into the intermembrane space,
This action creates a huge concentration gradient of H+ between the matrix and intermembrane space.
The H + can only flow back into the matrix through the protein ATP synthase, which uses the kinetic energy of H+ flow to create ATP from ADP & Pi
Finally, at the end of the chain the electrons “jump off” the last carrier & combine with O2 to form H2O

10. Chemiosmosis & Oxidative Phosphorylation
Chemiosmosis can be described as the coupling of the redox reactions of the electron transport chain to ATP synthesis by setting up a concentration gradient of H+ ions across a membrane.
Chemiosmosis provides the energy for ATP synthesis via the flow of H+ ions across a membrane. This method of producing ATP is called oxidative phosphorylation.
The process of oxidative phosphorylation is different from the direct transfer of a Pi from one molecule to ADP – called substrate level phosphorylation - which we saw in glycolysis and Kreb’s cycle.

11. Cellular Respiration

12. Cellular Respiration
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13. Cellular Respiration: Final Totals
Energy yield from glucose metabolism
ATP produced via substrate level phosphorylation
Glycolysis – 2 ATP
Krebs Cycle – 2 ATP
ATP produced via chemiosmosis
2 NADH from glycolysis – 4-6 ATP
2 NADH from transition step – 6 ATP
6 NADH from Krebs Cycle – 18 ATP
2 FADH2 from Krebs Cycle – 4 ATP
TOTAL
36-38 ATP
Efficiency 36 ATP = 263 kcal 1 glucose = 686 kcal
39% of the energy in glucose is converted to ATP, the rest is lost as HEAT

14. Cellular Respiration

15. A FEW PRACTICE QUESTIONS
What are the 4 steps of aerobic cellular respiration & where do they specifically occur in the cell or mitochondria?
Describe the structure of a mitochondrion
What goes in & comes out of glycolysis, the transition reaction, & Krebs?
What is NADH?
Describe how ATP is synthesized in the ETS.
How does this synthesis compare with ATP synthesized in glycolysis?