Lecture 4 - ETC Flashcards
What is another name for the ETC?
Respiratory chain
What happens to the reduced electron carriers (NADH and FADH2) that are produced by glycolysis and TCA cycle?
They are re-oxidized in the mitochondrial membrane, which is coupled to ATP production
What is the terminal electron acceptor and what does it form?
- O2
- Forms H2O
How is ATP made in the ETC?
While electrons are carried through a series of proteins, protons accumulate between the inner and outer membranes spaces, forming a gradient across the membrane that is exploited by ATPase to make ATP
What occurs in the first complex of the ETC?
- NADH and H+ are oxidized to NAD+
- 4 H+ are pumped into the intermembrane space
What occurs in the second complex of the ETC?
Succinate is converted to fumarate
What occurs in the third complex of the ETC?
4H+ pumped into the intermembrane space
Does the intermembrane space or the matrix have a higher pH and a higher [H+]?
- Matrix has higher pH
- Intermembrane space has higher [H+], making it positie
What occurs in the fourth complex of the ETC?
- Cyt c aids in the oxidation of 1/2 O2 + 2H+ to H2O
- 2 H+ are pumped into the intermembrane space
What are the delta E and G values for the transfer of electrons from NADH to coenzyme Q (complex 1)?
- delta E = -0.36 V
- delta G = -69.5 kJ/mol
What are the delta E and G values for the transfer of electrons from coenzyme Q to Cyt C (complex 3)?
- delta E = 0.19 V
- delta G = -36.7 kJ/mol
What are the delta E and G values for the transfer of electrons from Cyt C to O2 (complex 4)?
- delta E = 0.58 V
- delta G = -111.6 kJ/mol
For the conversion of NAD+ to NADH, how are electrons transferred?
As a hydride ion (2 electrons, 1 proton)
What happens to electrons as they pass down the ETC?
They lose free energy, which is conserved by ATP synthase for ATP formation
What process forms ATP and what is it coupled to?
- Oxidative phosphorylation
- Coupled to ETC
Why are the complexes arranged the way they are in the ETC?
- So that a carrier can accept electrons from only one carrier and pass them to only one carrier
- Carriers with high negative reduction potentials pass electrons to carriers with high positive reduction potentials
What is found in complex 1?
- NADH dehydrogenase
- FMN flavoprotein
- FeS
- Coenzyme Q
What is found in complex 2?
Succinate dehydrogenase
What is found in complex 3?
- Cytochrome b and c1
- 11 proteins
What is found in complex 4?
Cytochrome oxidase (a and a3)
Describe the electron transfer that occurs in complex 2
Succinate dehydrogenase with FAD transfers electrons to CoQ
Electrons in ____ have high G; electrons in ____ have low G
NADH; water
How much ATP is formed when electrons are transferred from NADH to O2?
2.5 ATP
How much energy does succinate oxidation yield?
-150 kJ/mol, forming 1.5 ATP
How many H+’s must flow through the ATPase to form one ATP?
4
How is ATP released from the ATP-synthase complex?
Rotation of the base
How much ATP does 1 NADH produce and why?
- 2.5
- The return of 4 H+ into the matrix provides enough G for the synthesis of 1 ATP, so 10 H+ = 2.5 ATP
How much ATP does 1 succinate (FADH2) produce and why?
- 1.5
- The return of 4 H+ into the matrix provides enough G for the synthesis of 1 ATP, so 6 H+ = 1.5 ATP
How many H+’s are pumped into the intermembrane space from 1 NADH? Explain where the H+’s are pumped.
- 10
- 4 by complex 1, 4 by complex 3, and 2 by complex 4
How many H+’s are pumped into the intermembrane space from 1 FADH2? Explain where the H+’s are pumped.
- 6
- 4 by complex 3, and 2 by complex 4
How many electrons go through the ETC at a given time?
2
How much ATP does glycolysis produce?
- Produces 2 NADH, which amounts to 5 ATP
- Produces 2 ATP from substrate level phosphorylation
- Total = 7 ATP
How much ATP is produced from the conversion of pyruvate to acetyl CoA?
2 NADH are produced, which equals 5 ATP
How much ATP is produced from TCA cycle?
- 2 GTP, which equals 2 ATP
- 2 FADH2 from the ETC, which equals 3 ATP
- 6 NADH from the ETC, which equals 15 ATP
- Total = 20 ATP
