The movement of the ions like Nacl requires energy to move across the membrane. This is so because the movement of the ions is taking place from a region of lower concentration to higher concentration.
When the movement of the particles takes place opposite the gradient then the process requires energy.
The movement of the salt outside from the inside of the sea horse is an example of active transport.
It is used when a product of the reaction is used for regulate the reaction. Therefore when there is enough product like ATP in this situtation, there is no need to run the reaction.
