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Proteins - Coggle Diagram
Proteins
Structure
Tertiary structure
The chains coil/fold further. More bonds form between chains (hydrogen bonds and ionic bonds). Disulfide bridges form whenever two molecules of cysteine come close the sulfur atoms bond. This makes a single polypeptide chain.
Secondary structure
Hydrogen bonds form between the amino acids in the chains . This makes it either coil into an alpha helix or fold into a beta pleated sheet.
Quaternary structure
They are made of several different polypeptide chains held together by bonds. The quaternary structure is the way the chains are assembled (globular or fibrous).
Globular - compact, roughly spherical, non-polar hydrophobic R groups are orientated towards the centre of the protein away from the aqueous surroundings and their polar hydrophilic R groups orientate themselves on the outside of the protein, soluble in water,
Fibrous - long chains, cross-links, large number of hydrophobic R groups, insoluble in water.
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Functions
Enzymes
Roughly spherical due to tight folding of the polypeptide chains. Soluble and often have roles in metabolism.
Antibodies
Involved in the immune response. Made up of two light and two heavy polypeptide chains. They have variable regions and the amino acids vary.
Transport proteins
Channel proteins are present in cell membranes, contain hydrophobic and hydrophilic amino acids causing the protein to fold up and form a channel. These proteins transport ions and molecules across the membrane.
Structural proteins
Physically strong. They consist of long polypeptide chains, parallel to each other with cross-links. This included keratin and collagen.
Biuret test
Needs an alkaline solution so add sodium hydroxide solution mixed with copper(II) sulfate solution or Biuret solution.
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Condensation reaction
Amino acids are linked together by condensation reactions. They create peptide bonds and a molecule of water.
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