Protein structure

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Define "amphipathic"
having both hydrophobic and hydrophilic residues
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How is alpha-keratin arranged?
2 amphipathic helices coiled with polar/hydrophilic side chains in the centre
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What binding is involved in helix-turn-helix supersecondary structures?
DNA binding
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What binding is involved in helix-loop-helix supersecondary structures (EF hand)
Ca(2+) binding
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Define "tertiary structure"
The folding of polypeptides where the R-groups interact
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Name a covalent link found in a protein's tertiary structure
disulphide bonds
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What conditions are required to disrupt protein structure?
20-40 degrees, approx pH 7.2 (normal), ionic strength (e.g. KCl), denaturing agents (organic solvents, chaotropic agents), protease enzymes, UV/oxidative/radiation damage
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What is cataracts?
misfolded proteins (disruption of the tertiary structure) in the eye
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What is hydrophobic collapse?
non-polar amino acids cluster into the core of a protein, so the protein can form hydrogen bonds with water (solubility)
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What are Pi-bond interactions / Pi-overlap / Pi-stack?
The mixing of clouds of pi electrons in aromatic amino acids.
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What is a salt bridge?
An ionic interaction between charhed protein residues (ineffective unless surrounded by hydrophobic interactions)
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What is the isoelectric point?
The pH where the side chain has no net charge
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Which amino acid functional group is affected in acidic conditions?
the amino groups gains a hydrogen
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Which amino acid functional group is affected in basic conditions?
the carboxyl group loses a hydrogen
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What is pKa?
the pH where 50% ionisation of an ionising group has occured
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What is the Henderson Hasselbach equation?
describes the relationship between pH, pKa and the extent of ionisation of a weak acid
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What type of proteins include disulphide bonds?
extracellular (robust) proteins
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Where are disulphide bonds found in the cell?
the ER, where oxygen is present
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What is the Afinsen Experiment?
The reduction/breaking of native disulphide bonds in ribonuclease, oxidation/formation of different structure, then reformation of original structure with 99% activity regained.
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What does the Alfinsen Experiment show?
the folded, active form of a protein has the lowest free energy. and that all the information needed to produce this structure is encoded in the protein's primary structure.
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What is protein disulphide isomerase (PDI)?
an enzyme that makes and breaks disulphide bonds until the correct arrangement is achieved
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Other cards in this set

Card 2

Front

How is alpha-keratin arranged?

Back

2 amphipathic helices coiled with polar/hydrophilic side chains in the centre

Card 3

Front

What binding is involved in helix-turn-helix supersecondary structures?

Back

Preview of the front of card 3

Card 4

Front

What binding is involved in helix-loop-helix supersecondary structures (EF hand)

Back

Preview of the front of card 4

Card 5

Front

Define "tertiary structure"

Back

Preview of the front of card 5
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