 Nucleic acids. Nucleic acids are one of the most important biomolecules which are present in the living organisms and they act as repositories for the genetic information in the living organisms. Although nucleic acids and their components have a number of functions to perform in the cell but the main function is the storage and transmission of genetic information in the living organisms and this storage and transmission of genetic information is one of the fundamentals of to sustain life. Like proteins and polysaccharides nucleic acids are also polymeric compounds as you know proteins are the polymers of amino acids. Mino acids are the building blocks of proteins. Similarly polysaccharides such as starch and cellulose they are made up of repeating units of glucose. So glucose is the building block of polysaccharides like starch and cellulose. Similarly nucleotides are the repeating units in our nucleic acid. So nucleic acids are the polymeric compounds which are made up of nucleotides. Nucleic acids are mainly of two types. These are ribonucleic acids and deoxyribonucleic acids. Ribonucleic acid is abbreviated as RNA while deoxyribonucleic acid is generally abbreviated as DNA. There are three types of RNAs. These are tRNA, transfer RNA, ribosomal RNA, RRNA and messenger RNA, mRNA. They have a number of functions to perform in the cell mainly during the protein synthesis. While deoxyribonucleic acids DNA they are only of one type. There are no other types of DNA and they are mainly present in the nucleus in addition to chloroplast and mitochondria. As you know the protein sequence, the sequence of amino acids in a protein molecule that depends on the nucleotide sequence in the DNA molecule. So DNA molecule describes the amino acid sequence of a protein. Similarly the nucleotide sequence of a mRNA. These are dictated by the nucleotide sequence of DNA. So a segment of DNA which is responsible for the synthesis or production of a functional product either mRNA or a protein. This segment of DNA is called a gene. So as you know there are thousands of genes in an organism. So obviously the DNA molecule contains thousands of genes so it will be a long molecule.