Oxidative Phosphorylation

Question 1

Where does oxidative phosphorylation take place?

Answer 1

The inner mitochondrial membrane

Question 2

How many protein pumps are involved in the ETC?

Answer 2

. 3 protein pumps involved

. Complex I, III (cytochrome C reductase), IV (cytochrome C oxidase)

Question 3

Which enzyme links oxidative phosphorylation to the TCA cycle? How so?

Answer 3

. Succinate dehydrogenase (complex II)

. Catalyses the conversion of succinate to fumarate in the TCA cycle, which yields FADH2

Question 4

Name two enzymes involved in oxidative phosphorylation.

Answer 4

Succinate dehydrogenase and ATPase

Question 5

Name the two intermediate small components involved in the ETC.

Answer 5

CoQ and Cytochrome C

Question 6

What is the role of complex I?

Answer 6

. Accepts electrons from NADH and transfers them to CoQ via Fe-S proteins
. Pumps out 4 protons into intermembrane space

Question 7

What is the role of complex II? Give another name for complex II

Answer 7

. Accepts electrons from FADH2 and transfers them to CoQ via Fe-S proteins
. Succinate dehydrogenase, link to TCA cycle

Question 8

What is the role of complex IV? Give another name for complex IV.

Answer 8

. Accepts electrons from cytochrome C (oxidising it) and transfers them to 1/2 O2, which is reduced to water
. Pumps out 8 protons into intermembrane space
. Cytochrome C oxidase

Question 9

What is the role of complex III? Give another name for complex III.

Answer 9

. Accepts electrons from CoQ and transfers them to cytochrome C (reducing it)
. Pumps 2 protons into intermembrane space
. Cytochrome C reductase

Question 10

What is the role of complex V? Give another name for this complex.

Answer 10

. Catalyses conversion of ADP+ Pi to ATP

. ATPase

Question 11

Describe the structure of ATPase and how this relates to its function.

Answer 11

. Consists of F0 and F1 region
. F0 is a coupling factor and channel protein which allows protons from the intermembrane space to pass into the mitochondrial matrix
. As the protons move down their concentration gradient through F0, they cause the C-ring of F0 to rotate
. This causes a conformational change in the beta subunit of F1
. ADP and Pi can then bind to F1, which catalyses the conversion to ATP

Question 12

Name two types of agent that can affect oxidative phosphorylation.

Answer 12

. ATPase inhibitors e.g. oligomycin

. Uncouplers- neutralise proton gradient, which inhibits synthesis of ATP)