The Chemistry of Molecular The Chemistry of Molecular BiologyBiology

Mary O’Brien

September 23, 2003

Chemical Structures of Cells

• Proteins– Amino Acids

• Nucleic Acids– Nucleotides

• Polysaccharides– Monosaccharides

The Basics of Amino Acids

• 20 amino acids• All amino acids in

nature are L form

• Structure consists of C, to which an amino group, a carboxyl group, a hydrogen atom, and a variable group

• Amino acids are classed according to their R group

From Amino Acids to Proteinpeptide bond peptide bond

isoleucinylphenylalanylalanineILE-PHE-ALA

The Structure of Nucleotides

• Common structure of phosphate group, base, five-carbon sugar

• Sugar is either DNA or RNA

• Bases are adenine, guanine, cytosine, thymine (DNA), uracil (RNA)

sugar

base

phosphategroup

Nucleotides Build Nucleic Acids

• 1’ carbon atom of sugar attaches to nitrogen of purine or pyrimidine• Acidic nature due to phosphate group • Nucleotides are linked by phosphodiester bonds

The Simplicity of Monosaccharides

• Carbohydrates of combinations of carbon and water in a one-to-one ratio

• Except for fructose, all sugars are in nature are D form

• D-Glucose (C6H12O6) is primary energy source

The Complexity of Polysaccharides

• Disaccharides are simplest polysaccharides• Anomeric carbon of one sugar molecule is linked to hydroxyl oxygen of another sugar molecule• Polysaccharides can contain dozens to hundreds of monosaccharides

Biological Macromolecules

• Multiple small molecules are covalently linked to form polymers

• Amino acids make proteins, nucleotides form nucleic acids, and polysaccharides are made of monosaccharides