I'm assuming that from the nature of the question (especially that it says proteins, DNA *AND* RNA, yet it looks like a short-answer rather than essay question that this is not after reams of information about each.
The structure of biological polymers, by definition, is that they are made up of smaller "monomer" units, which are chemically bonded to each other to make the long polymer strands. In proteins, the monomers are amino acids, in RNA and DNA the monomer units are nucleotides (in RNA, the nucleotides are made up of a phosphate group, a base and a ribose sugar, while in DNA the nucleotides are made up of a phosphate group, a base and a deoxyribose sugar unit).
The function of biological polymers (this is an odd question.. they don't have a funstion "as a polymer", just the separate functions that the substances happen to have) varies. DNA is what the genetic code is wirtten into. (m)RNA forms a"working copy" of this code to be used in protein synthesis. tRNA and rRNA are involved along with mRNA in translation. Proteins form enzymes to speed up biological reactions and to allow them to occur under the conditions present in living things, as well as forming various structural substances such as elastic and collagen which provide structural suport in skin and other tissues.