What kind of molecules are nucleotides and nucleic acids and what are they made of? This article covers the basics.

Inorganic and Organic Molecules

Although you can find many varying definitions, inorganic molecules are essentially substances that don’t have carbon-hydrogen (C-H) bonds, whereas organic molecules do contain carbon-hydrogen bonds and are found in living things.

The major classes of organic molecule include carbohydrates, proteins, lipids and nucleic acids.

Nucleic Acid Structure

Nucleotides are the building blocks of nucleic acids. Each monomer of nucleic acid, is called a nucleotide, and consists of 3 portions:

• a pentose sugar
• one or more phosphate groups
• one of five cyclic nitrogenous bases

ATP: The Energy Transfer Molecule

Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide, most important as the "molecular currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism. These molecules can transport energy because phosphate bonds contain a lot of potential energy, which is released when they are broken.

ATP is produced during photosynthesis and cellular respiration and is consumed by a multitude of cellular processes. It is also incorporated into nucleic acids in DNA replication and transcription.

Ribonucleic Acids: Genetic Material

Nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the genetic material of cells. Their names are derived from the type of sugar, ribose, contained within these molecules.

Phosphate-Sugar Backbone

Nucleotides linked together by covalent bonds between the phosphate of one nucleotide and the sugar of next. These linked monomers become the phosphate-sugar backbone of nucleic acids. Nitrogenous bases extending from this phosphate-sugar backbone like teeth of a comb.

The Twisted “Ladder” of Nucleic Acid

Hydrogen bonds form between specific bases of two nucleic acid chains, forming a stable, double-stranded DNA molecule, which looks like a ladder. Three H bonds form between bases cytosine (C) and guanine (G), which always pair up together between two nucleic acid chains. Two H bonds form between adenine (A) and thymine (T) in DNA or adenine and uracil (U) in RNA molecules.

The structure is analogous to a ladder, with the two deoxyribose-phosphate chains as side rails and the base pairs, linked by hydrogen bonds, forming the rungs. Hydrogen bonding also twists the phosphate-deoxyribose backbones into a helix, thus typical DNA is a double helix.

Additional Organic Chemistry Resources

To learn more about cell biology and organic chemisty and molecules, see the Suite101 articles What Is a Lipid, Amino Acids & Proteins, What Is a Carbohydrate and What Are Organic Molecules. Other excellent sites for information on organic chemistry include Science Prof Online and the Organic Chemistry Help site.

Sources

Bauman, R. (2005) Microbiology.

Park Talaro, K. (2008) Foundations in Microbiology.