核酸（Nucleic Acids）是一种主要位于细胞核内的大型生物分子，其充当着生物体遗传信息的携带和传递。核酸的单体结构为核苷酸。每一个核苷酸分子有三部分组成：一个五碳糖、一个含氮碱基、和一个磷酸基。如果糖是脱氧核糖，该聚合物是DNA。如果糖是核糖，该聚合物是RNA。当糖和含氮碱基得到组合时，它们形成核苷酸。核苷酸也被称为核苷酸磷酸盐。

核酸是最重要的生物大分子（其余为氨基酸/蛋白质，糖/碳水化合物，脂质和/脂肪）。它们大量存在于所有活的东西，功能有编码，传递和表达遗传信息 - 换句话说，信息通过核酸串行被传递。DNA分子含有生物物种的所有遗传信息，为双链分子，其中大多数是链状结构大分子，也有少部分呈环状结构，分子量一般都很大。RNA主要是负责DNA遗传信息的翻译和表达，为单链分子，分子量要比DNA小得多。

Nucleic acids are biopolymers, or large biomolecules, essential for all known forms of life. Nucleic acids, which include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are made from monomers known as nucleotides. Each nucleotide has three components: a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is deoxyribose, the polymer is DNA. If the sugar is ribose, the polymer is RNA. When all three components are combined, they form a nucleic acid. Nucleotides are also known as phosphate nucleotides.