The primary function of molecular membranes is the transport of ions and molecules into and out of cells. The movement of molecules from areas of low concentration to those of high concentration against chemical gradients is best described as

Active Transport

Explanation:

A cell uses energy for the movement of substances against a concentration gradient or an electrochemical gradient that maintains a balanced concentration of ions and molecules in living cells. This transport of substances is known as Active transport mechanisms which are the basic function of the cell membranes. The energy used is in the form of ATP.  Active transport occurs when there is a difference in the concentration of particles on both sides.

Okay well gravitational energy is matter forced by gravity making energy though the kinetic energy then the electric energy produces electricity from the kinetic energy and the kinetic energy gets its energy from the gravitational energy. was that the answer you wanted or something else?  

Answer    "a salt" would be the best answerexplanationsalts can be defined as ionic compounds that are neither acids nor bases. nacl is an example of a salt, and its ionic.an enzyme is an organic compound which is covalently bonded, not ionically bonded.acids are generally held together by covalent bondsan element does not need any bonds to exist