1. Proteins
Ms Glasgow

2. Proteins- gps of organic compounds consisting of C, H, O & Sometimes S
The monomer is an amino acid
The amino acid has a chiral carbon

3. Peptide Bonding

4. Categories of Amino Acids

5. What happens when amino acids reacts with water?
Answer:
Zwitterion formed (contains separate parts which are +vely & - vely charged)
Reason:
Internal transfer of a hydrogen ion from the -COOH group to the -NH2 group -> ion with both a -ve charge & a +ive charge
In acidic solutions:
 The -COO- part of the zwitterion picks up a hydrogen ion, resulting in a +vely charged amino acid (Left)
In basic solutions:
The hydrogen ion is removed from the -NH3+group, resulting in a –vely charged amino acid (right)
Conclusion:
The zwitterion acts as a pH buffer ( able to resist changes in the pH of its surrounding)

6. Hydrogen Bonds
Formed between R groups w/h are dipoles e.g carboxyl, hydroxyl & amino groups
Relatively weak bonds

7. Ionic Bonds
Formed between groups with opposite charge e.g ionised carboxyl and amino groups
Bond is stronger than H- bonds

8. Disulphide Bonds
Formed between R groups contain S - atoms e.g cysteine
Strong covalent bonds due to oxidation of 2 S – atoms by dehydrogenation

9. Hydrophobic Interactions
Formed with non-polar R groups e.g. tyrosine & valine
In aq. Sol’n -> hydrophobic group gathers in the interior away from water while hydrophilic group forms an outer shield towards the water

10. Protein Structure

11. Haemoglobin (Globular Protein)
Carries O2 in RBC
Consists of 4 separate polypeptides
2 alpha (141 aa) & 2 beta chains (146 aa)
1 haem gp with 1 O2 per chain
Soluble in water re: hydrophobic side gp inward but hydrophilic side gp outward towards water
Sickle cell anaemia <- mutation <- hydrophilic R group is replaced by a hydrophobic R group

12. Collagen (Fibrous Protein)
Component of connective tissues such as tendons & blood vessels & binds inorganic crystals
Consists of 3 polypeptide chains
Each chain of repetitions of 3 aa (proline, glycine, alanine)
Insoluble in water re: long (1000 aa) & hydrophobic R gps
Assemble into flexible fibres w/h cannot stretch

13. Food test

14. Reducing Sugars

15. Non-reducing Sugars

16. Starch

17. Protein

18. Lipids