Ok hydrogen ion gradient drives ATP synthase. In secondary active transport the preexisting concentration gradient drives the molecules.

 

My question is what do they mean when they say concentration gradient provides energy to do this. Is it the movement of ions like hyrdogen from high to low that results in energy.

 

When the concentration on each side is the same why is there no energy!!

 

Thanks!!

Hm, cells have sodium/potassium pumps to maintain a gradient between inside and outside the cell. An H+ gradient would be at the mitochondria (or in bacterial cells).

If the ion concentration on both sides are equal there is not gradient through which the molecules would move. If a gradient is made by pumps the molecules would diffuse freely from higher to lower concentrated areas. This can be harnessed by specialized proteins. And just btw. proton pumps have also been found to play a role in regulating the membrane potential.

Thanks