Physio question

[dentheartthrob]

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which of the following occur when active transport is involved in the movement of a solute accross a biological membrane?

a. expenditure of metabolic energy
b. a gain in free energy by the system
c. a unidirectional movement of the solute
d. movement of the solute against a concentration gradient

the answer from the packet is all of the above, for the most part I understand a, c, and d. but how does it gain free energy?

 

[katforx]

my guess :
free system energy is gained from the metabolism of carbohydrates, proteins and fats. active transport is ATP-coupled.

 

[Sprgrover]

Free energy can be obtained when the solute moves with its concentration gradient back across the membrane - active transport can create a membrane potential.