Amino acids are the building blocks of proteins. They contain both acidic and basic groups that allow them to polymerize and form peptide bonds, assembling into linear chains known as polypeptides or proteins. There are 20 common amino acids that make up proteins, which can be classified based on their variable R groups into nonpolar, aromatic, polar uncharged, positively charged, and negatively charged categories. Proteins perform a wide variety of important biological functions in the body as enzymes, structural components, binding proteins, hormones, and more.

1. Amino Acids, Peptides and Proteins

2. Proteins: Enzymes, Binding Proteins, Structural
Proteins – all made from Amino Acids

3. Amino Acids:
Building Blocks of Protein
• Proteins are linear heteropolymers of -amino acids
• Amino acids have properties that are well-suited to carry
out a variety of biological functions
– Capacity to polymerize
– Useful acid-base properties
– Varied physical properties
– Varied chemical functionality

4. Amino acids share many features,
differing only at the R substituent

5. L and D forms

6. Carbon Numbering System
A

7. Amino Acids: Classification
Common amino acids can be placed in five basic
groups depending on their R substituents:
• Nonpolar, aliphatic (7)
• Aromatic (3)
• Polar, uncharged (5)
• Positively charged (3)
• Negatively charged (2)

8. Invented the One Letter
Amino Acid Code.

14. Spectrophotometry

15. UV light Absorption by Proteins – due to 2 Amino Acids

16. Cysteine can form Disulfide Bonds

17. Uncommon Amino Acids

18. Amino acids in Proteins Can be Reversibly Modified
A

19. Non Protein Amino Acids

20. Toxic Amino Acids
A search for compounds producing Yunnan
Sudden Unexplained Deaths found related to
eating a mushroom.
Trogia venenata Zhu LHalford, B. C+E News Feb 13, 2012

21. Which Form Occurs in Water ?
An amino acid contains both acidic (carboxylic acid fragment) and
basic (amine fragment) centres. The isomer on the right is a zwitterion.

22. Peptide Bond Formation

23. Structure of a Simple Peptide
Ser-Gly-Tyr-Ala-Leu or SGYAL

24. Naming peptides:
start at the N-terminus
• Using full amino acid names
– Serylglycyltyrosylalanylleucine
• Using the three-letter code abbreviation
– Ser-Gly-Tyr-Ala-Leu
• For longer peptides (like proteins) the one-
letter code can be used
– SGYAL

25. AEGK

26. Aspartame
A

27. EXAMPLES: Peptides: A Variety of Functions
• Hormones and pheromones
– insulin (think sugar)
– oxytocin (think childbirth)
– sex-peptide (think fruit fly mating)
• Neuropeptides
– substance P (pain mediator)
• Antibiotics
– polymyxin B (for Gram – bacteria)
– bacitracin (for Gram + bacteria)
• Protection, e.g., toxins
– amanitin (mushrooms)
– conotoxin (cone snails)
– chlorotoxin (scorpions)

28. Proteins are:
• Polypeptides (covalently linked -amino acids) + possibly:
• cofactors
 functional non-amino acid component
 metal ions or organic molecules
• coenzymes
 organic cofactors
 NAD+ in lactate dehydrogenase
• prosthetic groups
 covalently attached cofactors
 heme in myoglobin
• other modifications