Practocal E

Question 1

Oxidative phosphorylation -

Answer 1

the process in the mitochondria by which adenosine diphosphate (ADP) is phosphorylated to ATP

Question 2

Oxidative phosphorylation is linked (or coupled) to ….

Answer 2

the flow of electrons from NADH or FADH2 through a series of electron carriers (the electron transport chain) in the inner mitochondrial membrane, resulting in the final reduction of oxygen to water.

Question 3

Oxidative phosphorylation - describe the process of setting up a hydrogen ion gradient:

Answer 3

A pair of electrons, arising from either NADH or FADH2, reduces one atom of oxygen to water. As electrons move down the chain hydrogen ions (H+) are moved across the membrane setting up an hydrogen ion gradient. This establishes a membrane potential. The concentration of hydrogen ions outside the inner membrane cannot be increased indefinitely as the membrane potential and hydrogen ion gradient reach limiting values and no more H+ can move. When this happens electrons cannot flow and no oxygen is used.

Question 4

The hydrogen ions and ATP synthase:

Answer 4

The hydrogen ions normally flow back down their concentration gradient and as they do so ATP synthase converts ADP + Pi to ATP.

Question 5

ATP synthase is a …

Answer 5

molecular motor driven by the movement of hydrogen ions back into the matrix.

Question 6

Describe why phosphorylation of ADP and electron transport are coupled:

Answer 6

If there is no H+ gradient ATP cannot be synthesised.

Similarly if there is no ADP and Pi the H+ ions cannot flow back into the matrix and electron transport stops:

Question 7

The electron transport chain consists of four protein complexes and two mobile electron carriers. Three of the four complexes are hydrogen ion pumps.

Answer 7

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