Lecture 30 - Oxidative Phosphorylation: ATP synthase

Question 1

What is the proton-motive force (pmf)?

Answer 1

A force created across the inner mitochondrial membrane from the proton gradient, the electrochemical graidient poduced by H+ imbalance.

Question 2

What 2 energetic gradients create the pmf?

Answer 2

1. A chemical gradient or pH gradient due to different H+
   concentrations on either side of the membrane
2. An electrical gradient due to the charge difference across
   the membrane (positive in the intermembrane space,
   negative in the matrix)

Question 3

What type of gradient is the pmf?

Answer 3

Electrochemical

Question 4

What happens when mitochondria are isolated from cells and have the outer membrane removed?

Answer 4

• Electron transport chain still works
• But ATP is not made

Question 5

What is Bacteriorhodopsin?

Answer 5

A light inducible proton pump (pumps protons to make a proton gradient in light)

Question 6

What happens to the ATP synthase in a bacteriorhodopsin?

Answer 6

Makes ATP when light switched on

Question 7

Is there an electron transport chain in bacteriorhodopsin?

Answer 7

NO

Question 8

What is 2,4-Dinitrophenol (DNP)?

Answer 8

An uncoupler

Question 9

How does DNP uncouple?

Answer 9

Shuttles H+ from intermembrane space to the matrix dissipating the proton gradient

Question 10

WHat happens in the presence of DNP?

Answer 10

ETC functions, but no ATP is made (no H+ grad)

Question 11

What does DNP prove?

Answer 11

The pmf is necessary for ATP synthesis

Question 12

What does removing the outer mitochondrial membrane prove?

Answer 12

This proves than ATP is not synthesised in the ETC, and outer membrane is required for formation of pmf

Question 13

What does bacteriorhodposin prove?

Answer 13

The proton gradient is sufficient for ATP synthesis without the ETC

Question 14

What happens if you take DNP?

Answer 14

• Fuel molecules still undergo CAC, B-Oxidation, Pyruvate dehydrogenase
• But coenzymes are reduced
• ETC functions
• No ATP is made

Question 15

What happens to the energy stored in the pmf in presence of DNP?

Answer 15

Released in the form of heat rather than ATP

Question 16

What does the ETC do?

Answer 16

Produces a proton gradient

Question 17

What uses the proton gradient to generate ATP?

Answer 17

ATP synthase

Question 18

What are the two parts of the ATP synthase?

Answer 18

F1 & Fo

Question 19

Where is the F1 of the ATP synthase?

Answer 19

In the matrix

Question 20

Where is Fo of the ATP synthase?

Answer 20

In the inner mitochondrial membrane

Question 21

How does the F1Fo-ATP synthase work?

Answer 21

As a molecular motor, with proton flow driving rotor movement

Question 22

What is an immobilised ATP synthase linked to?

Answer 22

FLuorescent actin

Question 23

What does rotor movement do in the ATP synthase?

Answer 23

Causes conformational changes in the stator that drives ATP synthesis

Question 24

Which subunits in the F1FO-ATP synthase turn?

Answer 24

‘rotor subunits’

Question 25

Which subunits in the F1FO-ATP synthase do not turn?

Answer 25

‘stator subunits’

Question 26

Where in F1 does Movement of the rotor causes conformational changes?

Answer 26

The catalytic α and β subunits of F1

Question 27

What are the possible conformations in the catalytic α and β subunits of F1?

Answer 27

O = Open
L = Loose
T = Tight

Question 28

What happens in the O (open) conformation?

Answer 28

ATP release/ADP and Pi binding

Question 29

What happens in the L (loose) conformation?

Answer 29

Holds ADP and Pi in preparation for catalysis

Question 30

What happens during the T (tight) conformation?

Answer 30

Catalysis - Formation of ATP

Question 31

What is the order in which the rotor turns?

Answer 31

O -> L - > T - > O -> L etc.

Question 32

How many protons are required to produce 1 ATP?

Answer 32

4 protons

Question 33

How many protons get pumped into the IMS for 1 NADH?

Answer 33

10 protons

Question 34

How many protons get pumped into the IMS for 1 FADH2?

Answer 34

6 protons