Animation - Proton Pump

What is the use of a concentration gradient across a membrane?

When a molecule or an ion is moved across a membrane from an area of low concentration to an area of high concentration then a gradient is generated. This gradient can be chemical or it can also create a difference in electrical charge across the membrane if ions are involved. The concentration is a source of potential energy. The gradient is analogous to picking up objects that are on the floor and placing them on a table. The objects can now be pushed off and the energy of their fall can be used to perform a task, just as falling water can be used to generate electricity. The proton pump generates an electrical and chemical gradient that can be used to create ATP which can drive a large number of different biochemical reactions.

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