NUCLEIC ACIDS Functions: store and transfer hereditary information (DNA and RNA), and act as energy intermediates (ATP). The monomer of a nucleic acid is a nucleotide, which consists of a phosphate group, a 5-C sugar, and a nitrogen base. 1

NUCLEIC ACIDS Nucleotides link to form polymer strands of DNA or RNA. The phosphate group of one nucleotide forms a covalent bond with the sugar of the next nucleotide. This is called a phosphodiester linkage. 2

Nitrogen-Containing Bases There are two main types of nitrogen bases: purines: Large, double ring molecules found in both DNA and RNA. 3

Nitrogen-Containing Bases 2. Pyrimidines – Smaller, single ring molecules found in DNA and/or RNA. 4

DNA and RNA Comparison DNA RNA Phosphate Group Deoxyribose Sugar 4 Possible N-bases: A, G, C, and T 4 Possible N- bases: A, G, C, and U Phosphodiester bonds between nucleotides within strands Phosphodiester bonds between nucleotides Double Stranded: Two strands are bonded by hydrogen bonds between nitrogen bases. Single Stranded 5

DNA Double Helix Two DNA strands are joined together in a “double helix”. The nitrogen bases join together via hydrogen bonds: A & T always join, forming 2 H Bonds. C & G always join, forming 3 H Bonds. 6

DNA Double Helix The strands run opposite to one another – they are said to run antiparallel to each other. 7

ATP – Adenosine Triphosphate High-Energy Bonds Composed of adenosine (adenine and ribose) and 3 phosphate groups. The bonds between the phosphate groups contain a lot of energy. 8

ATP – Adenosine Triphosphate ATP Hydrolysis: ATP + H2O  ADP + Pi + 31 KJ energy. This is an exothermic reaction! This is a reversible reaction: ADP Condensation Reaction: ADP + Pi + energy  ATP + H2O 9

ATP – Adenosine Triphosphate 11