Chapter 21: Proton-Motive Force (Creating ATP)

ETC and ATP

Protons were pumped into intermembrane space during the ETC. A chemical and charge proton gradient is now established.

Two components of ATP Synthase

1. F0: embedded in inner mitochondrial membrane

2. F1: Contains the active sites for ATP and protrudes into matrix

Process of ATP Synthase

1. F0 channel has two subunits —> Subunit a and c

2. Protons are pumped through subunit a matrix half-channel

3. Go through conformation change with subunit C when transfered to an aspartic acid residue

4. This induces rotation, moving proton to the matrix facing half channel

5. Pumped out on other half-channel into matrix

C Subunit Rotation

• y and E subunits are connected to C subunit

• 8 subunits in humans

• 10 in yeast

• Spin rate 100 r/s

F1 Subunit

• 6 Subunits (3 Beta and 3 Alpha)

• Beta contain enzymatic activity (ADP, P1, ATP)

States of Beta Subunits

O: Empty (ADP +P1)

• After rotation ATP is released in O state

L: Loose (Bound to ADP and P1)

T: Tight (Bound to ATP)

Conformation of gamma subunit determines active state

Molecules moving through mitochondrial membrane Muscle

NADH able to enter through glycerol phosphate shuttle

• Protons move to FAD

• Moved to Q

• QH2 goes to Q cycle

• Creates ATP

Two glycerol 3-phosphate dehydrogenases

(Cytoplasmic and Mitochondrial)

Molecules move through mitochondrial membrane liver and heart

NADH doesn’t move to FAD and is more efficient

Malate Asparte Shuttle move electrons from NADH in heart and liver

How we get NAD into matrix

How we get ATP out of matrix into cytosol

one unit in one unit out (ATP and ADP)

ADP goes to matrix ATP goes to cytoplasm

Regulation of Oxidative Phosphorylation by ADP

Acceptor or respiratory control

• We have a lot of ATP, slow down enzymes and store pyruvate in fat stroage

Inhibitors and Uncouplers of Metabolism

2-4 Dinitrophenol

Uncouples UCP-1

Allows protons to pump out and does not create ATP in inner membrane

Heat is generated instead

Also form of weight loss drug