1. Aim: What is the electron transport chain?

2. What is the electron transport chain?
The final series of reactions in aerobic respiration are called the electron transport chain.
A) glycolysis + pyruvate oxidation to acetyl-CoA + Kreb’s cycle produce only 4 ATP (2 from glycolysis and 2 from Kreb’s) Substrate-level phosphorylation has occurred.
B) most of the energy is stored in high energy electrons carried by reduced NADH and reduced FADH2
C) the role of the electron transport chain is to extract energy from NADH and FADH2. This will also regenerate NAD+ and FAD+.

3. Details of the electron transport chain
1) The ETC (electron transport chain) is made up of a series of carrier molecules (flavoproteins and cytochromes)found on the inner membrane of the mitochondria (cristae)
2) Each protein carrier has a prosthetic group (non-protein center) attached. The prosthetic group can alternately gain or lose electrons.

4. Details of the electron transport chain
3) Reduced NADH releases its high energy electrons to a more electronegative FMN carrier. Some energy is used by FMN to pump 2 H+ out (into the outer compartment). This continues with the protein carrier cytochrome a3 and the membrane lipid co-enzyme Q.
4) The high energy electrons are passed from carrier to carrier. Some energy is used to pump more H+ out. This sets up a proton gradient (chemiosmotic gradient) with more H+ in the outer compartment (+) and less H+ in the inner compartment (-).

6. Details of the electron transport chain
5) The last acceptor of electrons is oxygen. Water is made.
6) ATP is generated by:
a) oxidative phosphorylation - the energy released as electrons “fall” to lower levels (oxidative) is used to synthesize ATP (phosphorylation)

7. Details of the electron transport chain
b) chemiosmosis - the accumulated H+ from the outer compartment moves by facilitated diffusion into the inner compartment.
Electrical energy generated allows ATP synthase (a membrane protein) to phosphorylate ATP.

8. A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and Pi.
ATP synthase uses the energy of an existing proton gradient to power ATP synthesis.
This proton gradient develops between the intermembrane space and the matrix.

9. Summary of Aerobic Respiration

10. Summary of Aerobic Respiration
Glycolysis produces 2 ATP net by substrate level phosphorylation. 2 NADH reduced are made. No CO2 are made.
The production of 2 Acetyl-Co A releases 2 CO2 molecules. 2 NADHreduced are made.
Two turns of Kreb’s cycle releases 4 CO2 molecules, creates 2 molecules of ATP, 6 NADHreduced and 2 FADHreduced
The electron transport chain transfers energy from NADH and FADH to produce 34 ATP ( 3 ATP per NADH and 2 ATP per FADH) by oxidative phosphorylation.

11. Summary of Aerobic Respiration
So…
Four ATP made (glycolysis – substrate-level)
2 ATP made (Kreb’s – substrate-level)
34 ATP made (ETC – oxidative phosphorylation)
Result: 40 ATP made – 2 ATP used during glycolysis yields a net of 38 ATP per glucose that is oxidized aerobically. (Some cells produce a net of 36 ATP because an additional two ATP are used to move pyruvate into the mitochondria)