Ion electrochemical gradients

Question 1

Define ion electrochemical gradient

Answer 1

combination of the electrical gradient and the chemical gradient associated with a particular charged solute

Question 2

How does coupling of electrochemical gradients facilitate cellular work?

Answer 2

Ion electrochemical gradients are stores of potential energy and energy associated with the movement of a charged solute down this gradient is liberated and can be harnessed by the cell to do work

Question 3

What is the main component of the H+ electrochemical gradient generated in mitochondria? why?

Answer 3

Electrical (invaginated membrane gives large surface area and capacity to store charge across membrane, electroneutral transporters move nutrients into lumen using the H+ gradient which dissipates the chemical but not electrical gradient)

Question 4

What is the main component of the H+ electrochemical gradient generated in chloroplasts? why?

Answer 4

Chemical (not invaginated so limits surface area for charge storage, membrane permeable to anions and cations to dissipate the build up of positive charge in the lumen due to H+ pumping, which allows accumulation of protons in lumen to generate pH gradient)

Question 5

Where are H+ pumped in mitochondria?

Answer 5

from matrix/lumen (N) to intermembrane space (P)

Question 6

Where are H+ pumped in chloroplast?

Answer 6

from stroma (N) to thylakoid space/lumen (P)

Question 7

Why is the H+ electrochemical gradient positive for chloroplasts, but negative for mitochondria?

Answer 7

electrochemical gradients are measured in the lumen with respect to the outside:
- mitochondria have negative lumen, chloroplasts have positive lumen because they pump H+ in opposite directions

Question 8

What are the units for electrochemical gradient?

Answer 8

Volts or KJ/mol