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20 Cards in this Set
- Front
- Back
Describe the composition of human body |
20% protein 20% skeleton 60% water |
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What is a protein? |
Essential organic compound made up of 1 or more chains of amino acids |
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What is the simplest amino acid? |
glycine |
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Which amino acids have hydroxyl groups and can be phosphorylated? |
Serine, threonine, tyrosine |
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Which amino acid has a sulfur group in side chain? |
cysteine |
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Which amino acids are basic? |
lysine and arginine (always protonated) histidine protonated below pH 6 |
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Which amino acids are negatively charged? |
Glutamic and Aspartic acid |
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What form are amino acids found in? |
L-form (all chiral) |
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How strong is a peptide bond? |
Kinetically stable - lifetime in aq is 1000 years |
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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 |
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How do disulphide bridges form? |
Cysteine in side chains are oxidised |
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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; peptide; vdW; hydrophobic interactions, hydrophobic side chains within interior of protein |
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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 |
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What are hydrophobic interactions? |
Hydrophobic side chains contained within interior of molecule
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What orientation are alpha helices? |
right handed due to L-amino acids |
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Describe structure of alpha helix? |
H-bonds between nH group and C=O group 4 amino acids along the chain 3.6 residues per helix turn Right handed helix |
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Describe the structure of beta pleated sheet |
Hydrogen bonds between 2 or more strands can be parallel or ant parallel |
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What do chaperones do? |
Ensure folding continues along most favourable pathway |
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What are common denaturants? |
Urea - breaks H-bonds 2-mercaptoethanol breaks disulfide |
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What is the tertiary structure of proteins? |
Arrangement of secondary structures into globular structures (domains) |