EXAM 2 - oxidative phosphorylation

overview of oxidative phosphorylation

• electrons from NADH and FADH2 → go to oxygen

• this creates a proton gradient

• the proton gradient is used to make atp

where does oxidative phosphorylation happen

• in the inner membrane of the mitochondria

• it has Cristae ridges (impermeable to most molecules)

• the inner membrane is the site of electron transport and ATP synthesis

energy and proton gradient

• electrons lose energy → that energy is used to pump protons (this creates a gradient)

• high H+ outside

• low H+ inside

electron transport chain

• happens in inner mitochondrial membrane

• uses protein complexes I, II, III, IV

protein complexes

• complex I, III, IV = proton pumps

• complex II = NOT A PROTON PUMP (delivers electrons from FADH2 → complex III)

• NADH uses more pumps → makes more atp

The proton gradient is an interconvertible form of free energy

• electron potential

• heat production

• NADPH synthesis

• ATP

• flagellar rotation

• active transport

atp synthase structure

1. ATPase knob (F1 unit)

2. membrane bound, transporting base (F0 unit)

what connects the units of atp synthase

1. rotor: spins F1

2. stator: interacts with spinning F1 unit

chemiosmosis

protons flowing back to make atp

simple flow of electron transport

• Electrons move

• Protons pumped out

• Protons flow back in → ATP made

The components of the electron-transport chain are arranged in complexes

• ETC proteins are grouped into complexes (I-IV)

• Electrons move in order of increasing “pull” (affinity)

• Each complex grabs electrons better than the last

• the complexes are proton pumps (1,2,3)

The high-potential electrons of NADH enter at NADH-Q oxidoreductase (Complex I)

• NADH gives electrons to Complex I

• Electrons → (Q → QH2)

• 4 protons pumped out

how is energy captured in complex 1

by moving electrons which pumps protons

Oxidation states of quinones

• Q = oxidized

• QH• = intermediate

• QH2 = reduced

• happens in inner mitochondrial membrane Q pool

Ubiquinol is the entry point for electrons from FADH2 of flavoproteins

• FADH2 gives electrons directly to Q → QH2

• skips complex 1 → makes less atp

Electrons flow from Ubiquinol to Cytochrome C (Complex III)

• QH₂ → Complex III → cytochrome c

📌 Important:

• Complex III pumps protons

Cytochrome C oxidase (Complex IV)

• Final step

• Electrons + O₂ → H₂O

The electron-transport chain

• NADH & FADH₂ (made by citric acid cycle) give electrons

• Electrons flow through respiratory chain → powers proton pumping

• Oxygen becomes water

A proton gradient powers ATP synthesis

the gradient is stored energy

Oxidative Phosphorylation can be inhibited at many stages

• uncoupling → made into heat instead of atp

• treatment for obesity

The rate of oxidative phosphorylation is determined by the need for ATP

• No ADP → ETC stops

• acceptor/respiratory control: the regulation of oxidative phosphorylation by ADP

ATP yield from the complete oxidation o f glucose

• yields 30 ATP total

• 26 are from oxidative phosphorylation

• the rest of the 4 are yielded from the metabolism of glucose in glycolysis and citric acid cycle

Cellular respiration is regulated by the need for ATP

• ATP is high → slow down

• ADP is high → speed up

Proton path through membrane

1. Enter

2. Spin ring

3. Exit into matrix

• the number of c subunits determines the number of protons required to synthesize a molecule of ATP.

Proton motion across the membrane drives the rotation of the c ring

• Protons bind → c-ring spins

• Proton movement = rotation

Binding-change mechanism

3 states of β subunits:

• O (open) → releases ATP

• L (loose) → holds ADP + Pi

• T (tight) → makes ATP

💡 EASY WAY:

• L = loading

• T = making

• O = releasing

ATP synthase assists in formation of cristae

• atp synthase helps shape inner membrane folds

• structure and function are connected

oxygens role

• its the final electron acceptor

• makes water

atp synthase

• enzyme that makes atp

• has 2 parts

  • F0: membrane (proton channel)

  • F1: makes atp

How ATP is Made

• Protons flow through ATP synthase

• This causes rotation

• Rotation → makes ATP

💡 SIMPLE:

• Proton flow = spinning = ATP

c ring

• Part of ATP synthase

• Number of subunits matters

• The number of c rings determines the number of protons required to synthesize a molecule of ATP.

• More subunits = need more protons = less efficient

uncoupling

If ETC ≠ ATP:
👉 Heat is made

Why do NADH electrons yield more energy?

because the electrons go through 3 proton pumps instead of 2

Purpose of ETC

generate proton gradient used to make ATP

What can proton gradients be used for?

• generate heat

• active transport

• synthesize ATP