Biology As Proteins,

3.1.2 As level proteins

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Amino acids

  • Amino acids are the monomers of proteins 

A monomer is a small molecule which can join together to make a polymer

  • 'Essential amino acids'

A amino acid that a animal cannot make (it is something you have to have in your diet)

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General Structure

  • This is the formula of a amino acid which must be learnt.  

  •     The H-N-H part is known as the amino group
  •     The COOH part is known as the carboxyl group
  •     The R group is a variable group and determines the property of an individual amino acid.
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Dipeptide - Two amino acids bonded together.

  • They are bonded together by a Condensation reaction. The reaction occurs between the carboxyl group of one amino acid and the amino group of another amino acid. This is seen below. The bond is called the peptide bond.


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Peptide bond

  • The peptide bond holds a dipeptide together. When the bond is formed water H20 is lost.

Features of the bond

  • Its stable/ strong
  • Hydrolysis ( breaking apart using water) is the only way to break them.
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Polypeptides/ Proteins

Polypeptide/ Proteins : Both lots of peptides joined together 


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Primary structure

  • Primary structure is the order or sequence of amino acids in a long polypeptide chain.
  • Insulin is a protein made up of two polypeptide chains (seen below)


  • In this polypeptide we can see that the two seperate polypeptide chains are held together by bonds. These bonds are called DISULPHIDE BONDS
  • Disulphide bonds are strong bonds however only some amino acids can make disulphide bonds
  • The primary structure is VERY important, if it is wrong the whole structre and unique shape of a protein changes.
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Secondary Structure 1

Bonds Involved in secondary structure:

  • Hydrogen bond - can be made between a lot odf amino acids. its quite a weak bond however there are lots of them making the structure strong.

Arrangements : 

Alpha Helix:- A very common strucutre, its very stable ( due to the presence of a lot of hydrogen bonds


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Secondary Structure 2

Beta pleated sheet ( a stable structure)

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Tertiary Structure

  • A tertiary structure is a single continuos peptide chaind in which several alpha helices tubes are arranged and parts of irregualr folding which allows it to turn and twist.
  • (
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Bonds involved in tertiary structures

  • The strucutre is very weak - if you heat up the structure, bonds break and tertiary structure falls apart.
  • Their may be a few bonds at various points which fold or bend this strucutre

Hydrogen bonds - weak and few off them

Hydrophobic bonds - weak and few of them

ionic bonds - weak and very few of them

Disulphide bonds - less easily broken than others (stronger) but very very few of them

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Quaternary Structure

  • Quaternary strucutre is a protein made up of 2 or more polypeptide chains
  • Its maintained by same sort of bonds as the tertiarry structure
  • Haemoglobin is an example of a protein with a quaternary strucutre

( different colours represent different chains

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Fiborous proteins

  • Make fibres (structural and muscle)
  • Not compact
  • Not soluble
  • Cannot make suspensions
  • Structiral fibres are mainly secondary structures but do not form tertiary structures


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Globular Proteins

  • Globular proteins include enzymes,transport molecules, antibodies, hormones
  • Form compact rounded shape (hence the name globular)
  • Can form suspension ( they can move in and out of blood and be secreted in and out of cells)
  • Alll form tertiary structures


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thank you i find it use full. do u go to dame allens schools?

Edward Pinches

Haha yes how did you know?


thanks , this was very useful!

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