Lecture 29 - The electron transport chain

Question 1

What is oxidative phosphorylation

Answer 1

It is the coupled process of electron transport through the ETC and the phosphorylation of ADP to ATP by ATP synthase

Question 2

What couples the two pathways in oxidative phosphorylation

Answer 2

The proton gradient, created by the ETC and used by ATP synthase, couples the two pathways

Question 3

Where in the mitochondria does the ETC takes place

Answer 3

In the inner mitochondrial membrane, in the mitochondria as it requires oxygen

Question 4

The location of ETC experiment inside mitochondria

Answer 4

1. Treat with strong detergent:
   - Solubilise all membranes
   - ETC does not work
   - ETC in a membrane
2. Treat with mild detergent:
   - Only removes the outer membrane
   - ETC still works
   - ETC is in the inner membrane

Question 5

What takes place in the matrix of Mitochondria

Answer 5

• CAC
• B oxidation
• Pyruvate dehydrogenase

Question 6

What is the role of electron carriers in the ETC

Answer 6

Electron carriers transfer electrons between complexes in the ETC, facilitating redox reactions an proton pumping

Question 7

what are the Two mobile carriers

Answer 7

• Ubiquinone (UQ) = Coenzyme Q (CoQ)
• Cytochrome C (cyt c)

Question 8

energy releasing through carriers

Answer 8

As electrons move to carriers with a higher reduction potential (oxygen has the highest reduction potential) energy is released

Question 9

Where do the reduced coenzymes that feed into the ETC come from

Answer 9

The reduced coenzymes (NADH and FADH2) are produced during glycolysis, pyruvate oxidation and CAC

Question 10

Electron flow through ETC direction

Answer 10

NADH -> Complex 1 - UQ - Complex 3 - cyt c - Complex 4 - O2
FADH2 -> Complex 2 - UQ - Complex 3 - Cyt c - Complex 4 - O2

Question 11

What is the result of energy released by electrons moving up their reduction potential in ETC

Answer 11

The energy is used to translocate protons across the inner mitochondrial membrane, building a proton gradient

Question 12

What happens if the ETC is inhibited

Answer 12

• Stop flow of electrons through the ETC
• No proton gradient formed (No ATP made)
• Build-up of reduced co-enzymes (NADH and FADH2) so no oxidising power for other pathways

Question 13

At which complex of the ETC is NADH oxidised

Answer 13

NADH is oxidised at complex 1, releasing two electrons into the ETC and pumping four protons across the membrane

Question 14

At which complex of the ETC is FADH2 oxidised and how many protons are pumped

Answer 14

FADH2 is oxidised at complex II, releasing two electrons but no protons are pumped at this complex

Question 15

Why is Succinate dehydrogenase SDH enzyme shared between the ETC and the CAC

Answer 15

SDH is part of Complex 2 in the ETC and catalyses the oxidation of succinate in the CAC linking both processes

Question 16

What reaction occurs at Comples 4 of the ETC

Answer 16

At complex 4 electrons reduce oxygen to form water

Question 17

What happens if the complex 1 is inhibited by rotenone

Answer 17

Rotenon inhibits electrons transfer from NADH to CoQ, halting electron flow, proton pumping and ATP production from NADH

Question 18

What happens if complex 4 is inhibited by cyanide

Answer 18

Cyanide prevents electron transfer to oxygen at complex 4, stopping the ETC, proton gradient formation and ATP synthesis

Question 19

What is the Q cycle in the ETC

Answer 19

The Q cycle refers to the transfer of electrons from CoQ to complex 3, facilitating proton pumping and electron transfer to Cyt C

Question 20

How does the ETC link to glycolysis and citric acid cycle

Answer 20

The ETC oxidises NADH and FADH2 produced in glycolysis and the citric acid cycle, converting their energy into a proton gradient for ATP synthesis.