Proteins

Question 1

What is a dipeptide?

Answer 1

• 2 amino acids join
• NH2 group bonds with COOH group
• Condensation reaction
• Peptide bond

Question 2

Primary Structure of Protein?

Answer 2

Order of amino acids, it is specific

Question 3

All I need to know about secondary structure of Proteins.

Answer 3

• Hydrogen bonding between Nδ- and Oδ- react with Hδ+
• Forms α-helix or β-pleated sheet
• α-helix shape when H bonds form between every 4th peptide bond
• β-pleated sheet shape forms when protein folds so 2 polypeptide chains are parallel
• Collagen and keratin have secondary structure
• H bonds can be broken by high temps and pH changes

Question 4

All I need to know about tertiary structures of Proteins.

Answer 4

• Hydrogen bonds (only R groups)
• Disulphide bonds (cysteine amino acids)
• Ionic bonds (charged R groups)
• Weak hydrophobic interactions (polar R groups)
• Common in globular proteins

Question 5

How do we hydrolyse proteins?

Answer 5

• Condensation Reaction
• H2O added to molecule
  Concentrated HCL used
• Mixture boiled for many hours
• With enzymes, at room temp

Question 6

All I need to know about Thin Layer Chromatography

Answer 6

• Amino acids identified by their varying R groups
• TLC plate sprayed with locating agent (staining amino acids) or illuminated by UV light
• Rf value calculated
• Compared to analytical data to deduce composition of mixtures
• If Rf values too similar for 2 amino acids, 2D TLC can be used
• Run through first solvent, turned 90 degrees and run through 2nd.
• 2 Rf values gives greater confidence determining amino acid