functions of protiens
- enzymes
- digestion ( trypsin, pepsin, amylase)
- metabolism
- transport and storage
- oxygen transport
- fatty acids transport
- iron storage
- structural support
- skin and bone (collagen)
- elastic ligaments (elastin)
- immune protection
- antibodys
- movment
- muscle contractions (actin and myosin)
- hormones
- blood glucose regulation ( insulin and glycogen)
Amino Acids
- Are the building blocks of proteins
- contains
- Carbon
- hydrogen
- oxygen
- Nitrogen
- and sometimes sulphur
- each amino acid consists of the central alpha
carbon to which the following groups are
- a hydrogen atom
- a carboxyl (COOH) group
- An amino (NH2) group
- a unique R group or side chain
- determines amino acid properties
- amino acids have two functional groups
- an amino functional group
- a carboxyl functional group
- properties of amino acid R groups
- non-polar
- have non polar R groups and are hydrophobic
- polar
- are hydrophilic, form weak hydrogen bonds
with other polar molecules of water
- some amino acids have charged R groups
- negatively charged amino acids are acidic
- positively charged amino acids are basic
protein stucture
- primary structure
- the sequence of amino acids in the polypeptide
- each amino acid is linked by peptide bonds
- disulphide bridges are also part of the primary
- important in protein folding
- secondary structure
- the areas of finding or coiling within a protien
- alpha helices
- beta pleated sheets
- amino acids interact non-covalently (hydrogen
bonding) between the amino acid side chains
- hydrogen bonding coils the polypeptide into a
stabilised secondry structure
- resulting in alpha helix
- or when polypeptides lie parallel to each other
beta pleated sheets
- alpha helices
- form when protein chains coil due to hydrogen
bonds which form between non-adjacent
backbone carbonyl groups and amide groups
- R groups all extend outside the helix
- beta pleated sheets
- form when protein chains form layers over each
- are stabilised between neighbouring
polypeptide chains
- are stabilised by hydrogen bonds between the
carbonyl O atom on one chain and the NH
group on the adjacent chain
- tertiary structure
- the final 3D shape of a protein
- the function of a protein depends on the
tertiary structure
- the forces which give rise to and stabilise the
tertiary structure are
- ionic bonds
- salt bridges and electrostatic interactions
between side chains of amino acids
- hydrogen bonding
- occurs between side chains between the
hydrogens on one amino acid
- hydrophobic interactions
- in water soluble proteins non-polar amino acids are located on the
hydrophobic inside of the molecule
- hydrophobic regions are further stabilised
by Van der Waals forces
- Quaternary structure
- involves the clustering of several individual
polypeptide chains into a final and precise 3D
- stabilisation of tertiary structure
formation of a protien
- the alpha carboxyl group is joined to the alpha
amino group of another amino acid
- leads to the formation of a chain of amino
acids called a peptide bond
- forms a peptide bond
- condensation reaction
main categories of proteins
- fibrous
- elongated molecules whose secondary
structure is the dominant structural feature
- insoluble in water and physically tough
- provide mechanical support to cells and to
entire organisms
- polypeptide chains form a single repetitive
structure which is twisted regularly and
arranged in bundles or sheets
- globular proteins
- are relatively sepherical
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