Lecture 4 - ETC

Question 1

What is another name for the ETC?

Answer 1

Respiratory chain

Question 2

What happens to the reduced electron carriers (NADH and FADH2) that are produced by glycolysis and TCA cycle?

Answer 2

They are re-oxidized in the mitochondrial membrane, which is coupled to ATP production

Question 3

What is the terminal electron acceptor and what does it form?

Answer 3

• O2

- Forms H2O

Question 4

How is ATP made in the ETC?

Answer 4

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

Question 5

What occurs in the first complex of the ETC?

Answer 5

• NADH and H+ are oxidized to NAD+

- 4 H+ are pumped into the intermembrane space

Question 6

What occurs in the second complex of the ETC?

Answer 6

Succinate is converted to fumarate

Question 7

What occurs in the third complex of the ETC?

Answer 7

4H+ pumped into the intermembrane space

Question 8

Does the intermembrane space or the matrix have a higher pH and a higher [H+]?

Answer 8

• Matrix has higher pH

- Intermembrane space has higher [H+], making it positie

Question 9

What occurs in the fourth complex of the ETC?

Answer 9

• Cyt c aids in the oxidation of 1/2 O2 + 2H+ to H2O

- 2 H+ are pumped into the intermembrane space

Question 10

What are the delta E and G values for the transfer of electrons from NADH to coenzyme Q (complex 1)?

Answer 10

• delta E = -0.36 V

- delta G = -69.5 kJ/mol

Question 11

What are the delta E and G values for the transfer of electrons from coenzyme Q to Cyt C (complex 3)?

Answer 11

• delta E = 0.19 V

- delta G = -36.7 kJ/mol

Question 12

What are the delta E and G values for the transfer of electrons from Cyt C to O2 (complex 4)?

Answer 12

• delta E = 0.58 V

- delta G = -111.6 kJ/mol

Question 13

For the conversion of NAD+ to NADH, how are electrons transferred?

Answer 13

As a hydride ion (2 electrons, 1 proton)

Question 14

What happens to electrons as they pass down the ETC?

Answer 14

They lose free energy, which is conserved by ATP synthase for ATP formation

Question 15

What process forms ATP and what is it coupled to?

Answer 15

• Oxidative phosphorylation

- Coupled to ETC

Question 16

Why are the complexes arranged the way they are in the ETC?

Answer 16

• 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

Question 17

What is found in complex 1?

Answer 17

• NADH dehydrogenase
• FMN flavoprotein
• FeS
• Coenzyme Q

Question 18

What is found in complex 2?

Answer 18

Succinate dehydrogenase

Question 19

What is found in complex 3?

Answer 19

• Cytochrome b and c1

- 11 proteins

Question 20

What is found in complex 4?

Answer 20

Cytochrome oxidase (a and a3)

Question 21

Describe the electron transfer that occurs in complex 2

Answer 21

Succinate dehydrogenase with FAD transfers electrons to CoQ

Question 22

Electrons in ____ have high G; electrons in ____ have low G

Answer 22

NADH; water

Question 23

How much ATP is formed when electrons are transferred from NADH to O2?

Answer 23

2.5 ATP

Question 24

How much energy does succinate oxidation yield?

Answer 24

-150 kJ/mol, forming 1.5 ATP

Question 25

How many H+’s must flow through the ATPase to form one ATP?

Answer 25

4

Question 26

How is ATP released from the ATP-synthase complex?

Answer 26

Rotation of the base

Question 27

How much ATP does 1 NADH produce and why?

Answer 27

• 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

Question 28

How much ATP does 1 succinate (FADH2) produce and why?

Answer 28

• 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

Question 29

How many H+’s are pumped into the intermembrane space from 1 NADH? Explain where the H+’s are pumped.

Answer 29

• 10

- 4 by complex 1, 4 by complex 3, and 2 by complex 4

Question 30

How many H+’s are pumped into the intermembrane space from 1 FADH2? Explain where the H+’s are pumped.

Answer 30

• 6

- 4 by complex 3, and 2 by complex 4

Question 31

How many electrons go through the ETC at a given time?

Answer 31

2

Question 32

How much ATP does glycolysis produce?

Answer 32

• Produces 2 NADH, which amounts to 5 ATP
• Produces 2 ATP from substrate level phosphorylation
• Total = 7 ATP

Question 33

How much ATP is produced from the conversion of pyruvate to acetyl CoA?

Answer 33

2 NADH are produced, which equals 5 ATP

Question 34

How much ATP is produced from TCA cycle?

Answer 34

• 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