Revision biology - Proteins

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  • Created on: 21-05-10 13:15
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Revision ­ Proteins
Proteins are made from long chains of amino acids
A dipeptide is formed when 2 amino acids join together.
A polypeptide is when more than 2 amino acids join together.
Proteins are made from one or more polypeptides.
Different amino acids have a different variable group
All amino acids have the same general structure, a carboxyl group ­ COOH, an amine group ­ NH2 and
hydrogen. However there variable group ­ R differs.
General structure
R
|
H2N ­ C ­ COOH
|
H
Amino acids are joined together by peptide bonds
Amino acids are joined together by peptide bonds to form
dipeptides and polypeptides. In a condensation reaction, a water
molecule is released when a peptide bond is formed, and in the
reverse of this, a water molecule is used up to break the peptide
bond in a hydrolysis reaction.
Proteins - Structure levels and bonding
Structure level B
o
n
di
n
g
Primary structure ­ Sequence of amino H
acids in a polypeptide chain. el
d
t
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g
e
th
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p
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ti
d

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Secondary structure ­ Polypeptide H
chain doesn't remain flat and straight. el
H-bonds form between amino acids in d
the chain, making it coil into a -helix or t
fold into a -pleated sheet.…read more

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Tertiary structure ­ The coiled and Io
folded amino acid chains are coiled and ni
folded further. More bonds form c
between parts of the polypeptide in
chain.…read more

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Quaternary structure ­ Some proteins Influenced by all the bonds mentioned above.
are made of several different
polypeptide chains held together by
bonds. The quaternary structure is the
way these polypeptide chains are
assembled together.
Collagen
Collagen is a fibrous protein which is used as supportive tissue in organisms. It is made from 3
polypeptide chains coiled together to form a triple helix. The chains are interlinked by strong
covalent bonds. Minerals can bind to the triple helix to increase its rigidity.…read more

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