outer membraneinner membrane

matrix

red = respiratory chain proteins

green = ATP synthases

Figure 1. Location of enzymes involved in oxidative phosphorylation

cytoplasm

© OCR 2013

NADHNAD+

H+H+

H+

H+ H+

and ADPphosphate

ATP

outer membrane(permeable to H+

and has no role inoxidative phosphorylation)

inner membrane

Krebscycle

matrixcytoplasm

H+

red = respiratory-chain proteins

green = ATP synthase

Figure 2. The chemiosmotic theory of oxidative phosphorylation

O2

H2O

electron transport reactions

© OCR 2013

NAD+

NADH Aox

Ared

Krebscycle

Box

Notes: red = reduced; ox = oxidized The dashed red rectangle is the respiratory chain. The arrows show oxidation/reduction (electron transport) reactions. A, B, C, D are oxidation/reduction components (in reality, there are more). The respiratory chain can also be represented by a series of conventional equations:

Ared + Box Aox + Bred

Bred + Cox Box + Cred Cred + Dox Cox + Dred

Bred Cox

Cred Dox

Dred O2

H2O

Figure 3. Diagram of a respiratory chain

© OCR 2013

inner mitochondrial membrane

NADHNAD+

UQ

O2

H2O

Complex I

Complex IV

Complex III

cytochrome c

UQ = ubiquinone

matrix

Figure 4. “Stretch and challenge”: further details of the respiratory chain

inter-membrane space

electron transport reactions

red = respiratory chain proteins

Note that Complex II is involved in another branch of the respiratory chain which takes electrons from succinate to ubiquinone. It is not shown in this figure.

H+

H+

H+

H+

H+

H+

© OCR 2013