This is a process by which substances are transported across cell membranes by means of protein carried molecules

A transporter that is known as a membrane transport protein, which is a membrane protein that is connected with the motion of ions, small molecules, or macromolecules, like that of another protein, across a biological membrane. These transport proteins are essential and fundamental transmembrane proteins and they exist for good within and revolve the membrane across which they transport substances. The proteins may aid in the movement of substances by enabled diffusion or active transport. There are two main types of proteins that are associated with such transport, they are predominantly classified as either channels or carriers.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.