6-7 Amino Acids and translation

Fibrous proteins

• insoluble and provide structure

• cytoskeleton

• coatings (seeds)

• ie silk

Globular

• enzymes (catalysts)

• transport protein (haemoglobin)

• hormones (insulin)

• defense (antibodies)

• toxins (snake venom)

• Receptor (rhodopsin)

Amino acid: general structure

Zwitterionic

posesses both positive and negative charges

Chiral

amino acid property- only L amino acids exist in biology (glycine is not chiral)

Amino acid properties

• Zwitterionic

• Chiral

• range of sidechain / R groups

Aliphatic

• No charge on sidechain

• increasing in hydrophobicity with sidechain size

• Glycine, Alanine, Valine, Leucine, Isoleucine

Imino acid

• only amino acid with a secondary amine group present. all others primary amines

• sidechain from 5 membered ring- looping from the c alpha to the nitrogen

• confers diff properties on the polypeptide chain

• proline

Polar

• sidechains contains hydroxyl groups

• H-bond acceptors/ donors

• hydrophbic in nature

• Serine, Threonine

Basic

Lysine, Arginine, Histidine

Which amino acid has a pKa of 10

lysine

which amino acid has a pKa of 12

Arginine

which amino acid has a pKa of 6.5

Histidine

Acidic and amide derivatives

• change o- (carboxyl group) to H2N

• Aspartate, Aspargenine, Glutamate, Glutamine

Formation of a peptide bond:

Carboxylic acid reacts with amine

how do you estimate molecular mass of a protein

take number of amino acids and multiply by 110

how do you describe an amino acid

start at N- terminus (Amide) and then end at C terminus (hydroxyl group)