The Bacteriorhodopsin Proton Pump Uses Light Energy to Transport Protons

Question 1

what is the bacteriorhodopsin?

Answer 1

small integral membrane protein in the plasma membrane of archaea (also called purple synthetic bacteria)

Question 2

bacteriorhodopsin uses energy from photons of light to do what? What does this do?

Answer 2

drive active transport of protons out of the cells - creats an electrochemical proton gradient that powers synthesis of ATP by an ATP synthase

Question 3

What makes the bacteria purple?

Answer 3

light-absorbing pigment is retinal (related to vitamin A)

Question 4

Structure of bacteriorhodopsin?

Answer 4

has several alpha-helical membrane spanning segments forming a cylindrical shape

Question 5

Bacteriorhopsin function

Answer 5

• retinal chromophore is normally present in all-trans conformation, covalently linked to a lysine side chain (K 216)
• retinal absorbs a photon (one of its double bonds isomerases to a cis form, activation the bacteriorhodopsin molecule - photoactivated molecule then transfers protons to the outside of the cell)
• proton gradient produced by pumping protons out of the cell flow back into the cell down their concentration gradient, ATP synthesases produces ATP