Lecture 6 - Electrons

Where is the electron transport system (ETS) located in eukaryotic cells?

inner mitochondrial membrane

What is oxidative phosphorylation?

uses energy from electron transfer to produce atp

Where do the electrons entering the ETS come from?

nadh and fadh2

What is the final electron acceptor in the ETS?

oxygen, combines with electrons and protons to form water

How does electron flow help drive metabolism?

move through ets and release energy that transfer protons

Which has more energy, NADH or FADH₂?

nadh

What is the role of Complex I?

accepts electrons from nadh and transfers to q

How many protons does Complex I pump per NADH?

4 h

What are FMN and iron-sulphur centres used for in Complex I?

help transfer electrons

What are the three forms of ubiquinone?

ubiquinone oxidized form, semiquinone reduced form, ubiquinol reduced form

What is the role of ubiquinone?

carries electrons from complex 1 and 2 to complex 3

What is the role of Complex II?

receives electrons from succinate oxidation and transfers them to q, forming qh2

Does Complex II pump protons?

no, does not have enough energy

How do Complexes I and II connect to Complex III?

both transfer electrons to q

What is the role of Complex III?

receives electrons from qh2 and transfers them to cytochrome c

How many protons are transferred by Complex III per pair of electrons?

4 h transferred to intermembrane space side

Does Complex III directly pump protons?

no, through chemical reactions in q cycle

What is the role of cytochrome c?

carries electrons from complex 3 to 4

How many electrons does cytochrome c carry at a time?

one

What group does cytochrome c contain?

haem group

What is the role of Complex IV?

transfer electrons from cytochrome c to oxygen, forming water

How many protons does Complex IV pump per pair of electrons?

2 h

Which inhibitor blocks Complex I?

rotenone

Which inhibitor blocks Complex III?

antimycin a

Which inhibitor blocks Complex IV?

cyanide

What happens when an ETS complex is inhibited?

electron flow is blocked, carriers before reduced, carriers after oxidized

What are cytochromes?

electron transfer proteins containing metal groups, change oxidation state

How can scientists investigate electron flow using cytochromes?

colour and light absorbance change between oxidized and reduced states

How many protons are transferred per NADH entering the ETS?

10 total, complex 1 = 4, complex 3 = 4, complex 4 = 2

How many protons are transferred per FADH₂-linked input?

6 total, complex 3 = 4, complex 4 = 2