Oxidative phosphorylation

Question 1

What forms the chemiosmotic gradient?

Answer 1

The H+ pumped from the matrix to the intermembrane space. Here they are in very high concentration when compared to the matrix, resulting in a chemiosmotic gradient.

Question 2

How is oxidative phosphorylation a vectoral reaction?

Answer 2

A vectoral reaction is a reaction that has a specific spatial direction. The electrons are moved to the outer edge of the inner membrane and then passed down, alongside the H+, to the inner side. The reaction only occurs when it happens in this specific direction.

Question 3

What is the term given to the energy released by the H+ travelling down the gradient?

Answer 3

Proton motion force.

Question 4

What are the subunits of ATPsynthase and are they bound?

Answer 4

F0 is membrane bound subunit.

F1 is the protruding subunit.

Question 5

How does H+ pass through the F0 subunit?

Answer 5

Binds to the barrel and this causes a conformational change, whereby the barrel rotates, dropping the H+ into the F1.

Question 6

Which subunit of F1 binds the ADP and Pi?

Answer 6

The Beta complex

Question 7

How does the beta complex help to form ATP?

Answer 7

The F0 rotates and this causes a change in the conformation of the F1. This change results in ADP and Pi being jammed together and ATP being expelled.

Question 8

What id the majority of the proton motion force spent doing?

Answer 8

Expelling the newly formed ATP from the binding site.

Question 9

How many hydrogens are required to pass through ATPsynthase to form one molecuel of ATP?

Answer 9

3H+

Question 10

How many molecules of ATP does NADH help to synthesis?

Answer 10

~2.5

Question 11

How many molecules of ATP does FADH2 help to synthesise?

Answer 11

~1.5

Question 12

How many ATP molecules are formed from one glucose molecule, provided the glycerol phosphate shuttle isn’t used?

Answer 12

32

Question 13

How many ATP molecules are formed from one glucose molecule when the glycerol phosphate shuttle is used?

Answer 13

Approximately 30, but this can vary significantly depending on the extent to which the shuttle is used.

Question 14

What happens to the ETC if the inner membrane of the mitochondria becomes permeable to H+?

Answer 14

The ETC will still function, but the electrons energy will be released as heat, not to form the chemiosmotic gradient.

Question 15

What does ETC-ATPsynthesis decoupling result in?

Answer 15

Malignant hyperthermia.

Question 16

Which chemical is known to cause malignant hyperthermia?

Answer 16

Halothane.

Question 17

Which tissues make use of the ETC-ATPsynthesis decoupling and why?

Answer 17

Brown fat as [especially in newborns] it helps to keep them warm.