Chapter 8.1: Nucleic Acids – The “Basics”

CHEM 7784

Biochemistry

Professor Bensley

CHAPTER 8.1 Nucleic Acid Basics

– Biological function of nucleotides and nucleic acids– Structures of common nucleotides

Today’s Objective: (To learn and understand the)

Central Dogma of Biology

Nucleotides and Nucleosides

• Nucleobase = Nitrogeneous base

• Nucleoside = Nitrogeneous base + Pentose

• Nucleotide = Nitrogeneous base + Pentose + Phosphate

Pentoses of Nucleotides

• D-ribose (in RNA)

• 2-deoxy-D-ribose (in DNA)

• The difference?

2'-OH vs 2'-H

• This difference affects secondary structure and stability

Nitrogenous Bases

Nucleosides

Anti-conformation predominates in nucleic acid polymers

Phosphate group

• Negatively charged at neutral pH

• Typically attached to 5’ position

–Nucleic acids are built using 5’-triphosphates

–Nucleic acids contain one phosphate moiety per nucleotide

Nucleotides• Phosphate ester of nucleosides

The plane of the base is oriented perpendicular to the plane of the pentose group

Nomenclature

Nomenclature: Deoxyribonucleotides

You need to know structures, names and symbols (both two-letter (dA) and four-letter (dAMP) codes)

Nomenclature: Ribonucleotides

You need to know structures, names, and symbols (both one letter and three-letter codes)

Polynucleotides

Nucleotide monomers are joined by 3’-5’ phosphodiester linkages to form nucleic acid (polynucleotide) polymers

Base pairing evident in DNA compositions