Proton Gradients

Question 1

What is chemiosmosis?

Answer 1

The movement of ions across a selectively permeable membrane down their electrochemical gradient

Question 2

What are the 3 basic tenets of chemiosmotic hypothesis?

Answer 2

• Respiratpry and photosynthetic electron transfer chain should translocate protons
• ATP synthase should function as a reversible proton-translocating ATPase
• Energy trandsducing membranes should not be leaky

Question 3

In bacteria and mitochondria which direction are protons pumped?

Answer 3

From the inside to the outside

Question 4

In chloroplasts what direction are protons pumped?

Answer 4

From the inside to the outside

Question 5

Why in chloroplasts does Δψ not build up?

Answer 5

Because of compensatin cotranslation of Cl- ions or counter translation of Mg2+

Question 6

What are uncouplers?

Answer 6

Small molecules that are soluble in the membrane interior in both pronated and deprotonated forms

Question 7

How is energy lost when uncouplers are used?

Answer 7

Heat

Question 8

Give 3 examples of uncouplers

Answer 8

• CCCP
• FCCP
• 2,4-DNP

Question 9

What kind of molecule are CCCP and FCCP?

Answer 9

Lipid soluble weak acids, the positive charge of which is delocalised over the molecule

Question 10

In order to dissipate a pmf what has to happen to the anionic form of DNP?

Answer 10

It has to return to the cytosol via the membrane interior

Question 11

When is UCP1 useful?

Answer 11

For animals waking up from hiberation, to warm them up enough so they can start shivering