Water

• reactant
• solvent
• transport
• temperature control

The attraction between water molecules is called hydrogen bonding.

Water has a high specific water capacity as the hydrogen bonds can absorb a lot of energy. The bonds are also hard to break.

Hydrogen atoms are postively charged - Oxygen atoms are negative.

                           amino acid - dipeptide - polypeptide - protein

-made up of one or more polypeptides.

-the amino acids are linked together by peptide bonds 

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Primary Structure (peptide bonds)

• a sequence of amino acids in a polypeptide chain

Secondary Structure (hydrogen bonds)

• hydrogen bonds form between amino acids to make it coil
• alpha helix or beta pleated sheet

Tertiary Structure

• coiled further
• more bonds form
• for proteins from a single polypeptide structure this is the final structure.
• ionic interactions - attractions between charges on parts of the molecule
• disulfide bonds - between custeine

Quaternary Structure (all bonds)

• several polypeptide chains held together by bonds

Collagen

• strong fibrous protein for supportive tissues in animals
• three polypeptide chains
• strong triple helix
• covalent bonds interlinking chains
• minerals bind to the helix to increase its rigidity

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Haemoglobin

• globular protein
• iron containing heam group binds to oxygen
• transports O2 in the blood
• curled structure with a hydrophilic outside - soluble.