Chemiosmosis and ATP Synthase

Question 1

Define Chemiosmosis and Where the Energy comes from.

Answer 1

the movement of protons across the inner mitochondrial membrane, using the energy generated from ETC

Question 2

What is the Purpose of Chemiosmosis?

Answer 2

create a proton gradient and electric field

• drives ATP Synthase

Question 3

How do you Work out Proton Motive Force?

Answer 3

= change in pH + change in charge gradient

Question 4

describe the domain F0 of ATP synthase

Answer 4

F0
- in the inner mitochondrial membrane
- has a proton pore and subunits - a,b,c
- each C subunit = made up of a pair of helices, in the middle = aspartic acid
- when in contact with the membrane = neutral, doesn’t destabilise the membrane
- when in contact with the a subunit = negatively charged

• each b subunit = 2 half channels, so hydrogen can only diffuse in halfway

Question 5

Describe the F1 Domain of ATP Synthase and state its function

Answer 5

• in the mitochondrial matrix
• 5 subunits
• 3 alpha, 3 beta and 1 gamma = hexameter ring
• gamma is in the middle as the stalk, it rotates and determines the state
• in open state, ATP released
• in the tense state, ATP produced

function is to bind ADP+Pi

Question 6

How does ATP Synthase Work?

Answer 6

• aspartic acid from F0 in contact with alpha complex = negative charge
• movement of c subunit = impossible
• hydrogen is pushed into a subunit due to hydrogen gradient from inter membrane space
  = charge is not negative
  = c subunit rotates
• hydrogen from c subunit moves into mitochondria matrix
• charge negative and repeat

Question 7

Which Protein Moves ADP/ATP across the inner mitochondrial membrane?

Answer 7

ADP/ATP Translocase

Question 8

What is Thermogenin?

Answer 8

a unique uncoupling protein found in mitochondria

passes the F0F1 complex
- energy of oxidation is dissipated as heat instead

Question 9

What Evidence is there for how ATP Synthase works?

Answer 9

a genetically engineered F1 attached to a nickel complex
- Biotin was covalently attached to C on F0
- Avidin is bound to Biotin
- Avidin has fluorescent probe
- when ATP introduced, the activin moved

Question 10

What is Pharmacological Uncoupling? What Effect does it Have on Oxidation? What was Used? Why is it not Used Anymore?

Answer 10

an agent which uncouples the ETC by directly transporting protons across mitochondrial matrix

• NADH2 to O2 is unaffected
• ATP is NOT synthesised

2,4-dinitrophenol was used
- it was a photographic chemical, fertiliser, used in manufacturing of dyed and explosives

• banned as it is dangerous and unfit for human consumption

Question 11

Give Some Molecules which can Stop ETC. (4)

Answer 11

Rotenone
Antimycin A
Cyanide Ions
Carbon Monoxide