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20 Cards in this Set

  • Front
  • Back

Describe the composition of human body

20% protein

20% skeleton

60% water

What is a protein?

Essential organic compound made up of 1 or more chains of amino acids

What is the simplest amino acid?


Which amino acids have hydroxyl groups and can be phosphorylated?

Serine, threonine, tyrosine

Which amino acid has a sulfur group in side chain?


Which amino acids are basic?

lysine and arginine (always protonated)

histidine protonated below pH 6

Which amino acids are negatively charged?

Glutamic and Aspartic acid

What form are amino acids found in?

L-form (all chiral)

How strong is a peptide bond?

Kinetically stable - lifetime in aq is 1000 years

What is stearic hindrance?

Only conformations in which side chains don't clash with main chain are allowed

This is because no rotation about peptide bond but other bonds can rotate

C=O and NH in same plane of molecule

How do disulphide bridges form?

Cysteine in side chains are oxidised

What bonds hold proteins together?

Disulfide, cysteine in side chains oxidised to form a covalent bond;

hydrogen, 2 atoms with partial negative share hydrogen with partial positive;

ionic, electrostatic attraction between charged side chains;



hydrophobic interactions, hydrophobic side chains within interior of protein

Under what circumstances are ionic bonds in proteins strongest, and where are ionic bonds generally found?

IN interior of protein with no water

generally found on surface of protein so can be neutralised by counterion

What are hydrophobic interactions?

Hydrophobic side chains contained within interior of molecule

What orientation are alpha helices?

right handed due to L-amino acids

Describe structure of alpha helix?


between nH group and C=O group

4 amino acids along the chain

3.6 residues per helix turn

Right handed helix

Describe the structure of beta pleated sheet

Hydrogen bonds between 2 or more strands

can be parallel or ant parallel

What do chaperones do?

Ensure folding continues along most favourable pathway

What are common denaturants?

Urea - breaks H-bonds

2-mercaptoethanol breaks disulfide

What is the tertiary structure of proteins?

Arrangement of secondary structures into globular structures (domains)