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what is the biuret test used to determine?
whether a protein is present - it will go purple.
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what are AAs made up of?
carbon, hydrogen, oxygen, nitrogen
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what attaches to the central carbon atom?
-H -NH2 (amino) -COOH (carboxyl) -variable R group
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give 3 examples of AAs.
phenylalanine, aspartate, tyrosine
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what are polypeptides?
chains of AAs joined by polypeptide bonds between the carbon atom of one and the nitrogen atom of another
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what happens when two AAs join?
a dipeptide is formed
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what process is this?
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what is there at each end?
-a free amino group. -a free carboxyl group.
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what do polypeptides fold to form?
the 3D structure of working proteins
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what does the primary structure determine?
the ultimate shape thus function of the protein.
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what does one change in the sequence of AAs lead to?
a change in the proteins shape so that it can no longer carry out its function correctly.
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what is the secondary protein structure?
the shape formed by the AA chain when it first twists
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how is it stabilised?
by the formation of hydrogen bonds
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what shapes could it be?
-alpha helix > spiral shape. -beta pleated sheet > zig zags back and forth
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what is the tertiary structure?
the second level of folding that gives a complex, 3D structure.
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how is the structure maintained?
by hydrogen bonds and disulphide bridges
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what does the 3D shape do?
makes each structure distinctive allowing it to be recognised by other molecules.
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where does the quaternary structure occur?
in proteins that have more than one polypeptide chain and/or a non-protein group
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give an example.
haemoglobin contains haem which is an iron-containing group
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what do globular proteins do?
carry out metabolic functions
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how is their specific 3D shape essential to their role?
it makes the proteins specific to particular substrates/antigens/ions/molecules/receptors
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what roles to fibrous proteins have?
they have structural roles
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they look like ropes and are composed of many polypeptide chains which makes them strong.
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give examples.
-collagen>bones. -keratin>hair. -tubulin>cytoskeleton in cells. -actin>muscle.
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what happens if a gene mutates?
the function of the protein is non-existant
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the sequence of AAs has changed
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Card 2


what are AAs made up of?


carbon, hydrogen, oxygen, nitrogen

Card 3


what attaches to the central carbon atom?


Preview of the front of card 3

Card 4


give 3 examples of AAs.


Preview of the front of card 4

Card 5


what are polypeptides?


Preview of the front of card 5
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