Oxidative Phosphorylation and Proton Motive Force

A strong reducing agent readily donates elections and has a ___ E^0’

negative

A strong oxidizing agent readily accepts electrons and has a ___ E^0’

positive

___ shuttle transports NADH into the mitochondria in muscle tissue

Glycerol-3-phosphate

___ accepts electrons from cytosolic NADH in muscle tissue

DHAP

___ shuttle transports NADH into mitochondria in other tissues (other than muscle)

Malate-aspartate

___ accepts electrons from cytosolic NADH in other tissues (other than muscle)

Oxaloacetate

Components of the electron transport chain

I - NADH dehydrogenase

II - Succinate dehydrogenase

III - Cytochrome bc₁

IV - Cytochrome c oxidase

V - ATP synthase

Which components pump protons?

Complexes I, II, and III

Which are mobile the carriers?

1. Coenzyme Q (ubiquinone/Q) - carries electrons from Complex I and II → Complex III

2. Cytochrome C - carries electrons from Complex III to Complex IV

Why does NADH generate more ATP than FADH2?

NADH enters at Complex I (goes through 3 proton pumps → 2.5 ATP) pumps more ATP

FADH2 enters at Complex II (goes only through 2 proton pumps → 1.5 ATP)

How is the ETC couple to ATP synthesis?

1. ETC pumps protons into intermembrane space, generating a proton gradient

2. Protons flow back into the matrix through ATP synthase, and the energy is used to couple ADP + P_i → ATP

How does the rotation of the C ring lead to ATP synthesis?

1. The C ring (a part of F₀) rotates with proton flow

2. This rotation also turns the gamma shaft of F₁, causing conformational shifts in the beta subunits

3. These changes drive ATP synthesis

What happens in the open conformation of a beta subunit?

The subunit releases ATP and can accept ADP + Pi

What happens in the loose conformation of a beta subunit?

The subunit binds ADP and Pi

What happens in the tight conformation of a beta subunit?

The subunit tightly binds them and creates ATP

How is oxidative phosphorylation regulated?

Mainly regulated by acceptor charge (the concentration of ADP)

Higher [ADP] means ATP synthase and ETC speeds up

Lower [ADP] means ATP synthase and ETC slow down

How are ADP/ATP transported across the inner membrane?

ADP and ATP are exchanged by Adenine Nucleotide Translocase (ANT) (antiporter)

• ADP moves into mitochondrial matrix

• ATP moves out into cytosol

What is formed when oxygen accepts electrons and protons at the end of the ETC?

Water

According to the chemiosmotic hypothesis, what connected electron transport to ATP synthesis?

A proton gradient across the inner membrane

Which two components contribute to the proton-motive force

Chemical and electrical gradients

What directly causes the catalytic subunits of ATP synthase to change conformation?

Rotation of the gamma subunit

Which conformation of ATP synthase allows ATP to be released?

Open (O)

What is the function of ATP-ADP translocase

To exchange mitochondrial ATP for cytoplasmic ADP

Why is the inner mitochondrial membrane highly folded into structures called cristae?

To increase the surface area available for ETC

Iron transfers electrons by switching between __ and __

Fe2+; Fe3+

What is the primary function of the F₀ portion of ATP synthase?

To conduct protons and drive rotation

How is the rotation of the c ring connected to ATP synthesis?

IT drives the rotation of the gamma subunit