BIOL213 Lecture Notes - Lecture 1: Aliphatic Compound, Amine, Hydrogen Bond
Lecture 1 – Amino acids
Learning Goals:
1. Structure and naming of amino acids
2. Structure and properties of peptides
3. Ionisation behaviour of amino acids and peptides
4. The three-dimensional structure of proteins
5. Methods to characterise peptides and proteins.
• There are 20 common amino acids
• Glycine is the simplest amino acid
• Amino acids: have properties that are well-suited to carry out a variety of
biological functions.
• Free amino acid analogues are used as medicines; and are also used as supplements,
food additives, enhancers and preservatives.
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Lecture 1 – Amino acids
Amino acids are chiral (except glycine) - when you rotate them around you don’t get a
mirror image
(Chiral molecule: rotated molecule cannot be superimposed on its mirror image
Achiral molecule: rotated molecule can be superimposed on its mirror image)
Amino acid classification:
1. Nonpolar, aliphatic: side chains are hydrophobic; not soluble in water; isolated by
extraction with organic solvents.
2. Polar, uncharged R groups: can form hydrogen bonding; weakly polar; more
soluble in water than non-polar.
3. Aromatic R groups: can form hydrophobic interactions
4. Positively charged (basic) R group: strongly polar.
5. Negatively charged (acidic) R groups: strongly polar.
Modified amino acids in proteins: arise by post-translational modifications of proteins
(modification of an amino acid already incorporated into protein). Eg. Covalent
modification and reversible modifications.
Some modified amino acids are not found in proteins and are free. Eg. Dopamine, which
is a tyrosine
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