B1.2 Proteins
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what monomers make up proteins
amino acids
what determines the shape and function of the protein
the sequence, type and number of amino acids present
how many naturally occurring amino acids there
20
amino acid + amino acid
dipeptide
how many essential amino acids are there
9
what are essential amino acids
amino acids that can’t be synthesised
what does the genetic code (DNA base sequence) code for
the number and order of amino acids in a polypeptide
for a chain of 50 amino acids, how many possible combinations would there be
20^50
some roles of proteins
catalysis by enzymes blood clotting - interact w oxygen to form scab strengthen fibres in skin (collagen, keratin) immune system antibodies hormones
how does heat denaturation affect protein structure
heat causes vibrations within protein molecules, breaking intramolecular bonds so conformation changes irreversible
how does pH affect protein structure
pH change causes intramolecular bonds to break within the protein molecule
why is there a lot of chemical diversity between the amino acids
the r groups vary a lot between the 20 amino acids
role of r groups
determine properties of amino acids- acidic/basic, polar/non polar etc
___________ R groups are polar and can be either acidic or basic
Hydrophillic
what are proteins
relatively large complex molecules that contain one or more chains of amino acids known as polypeptides
what is primary structure
the sequence of amino acids in a polypeptide chain
what is secondary structure
the formation of secondary structures - alpha helices and beta pleated sheets
why do these secondary structures form
as a result of hydrogen bonding between different amino acids in the chain
what happens in the tertiary structure
how the secondary structures fold to form a 3d structure
what does the folding in the tertiary structure result from
the interactions between the r groups of the amino acids and the environment
what types of bonding are there in the tertiary structure
peptide bonds hydrogen bonds( r groups +amino+carboxyl groups) disulfide ionic hydrophobic interactions
are the amino acids in protein polar or non polar
non polar so less soluble in aqueous solutions
examples where non polar amino acids in protein are used for structural purposes
in the centre of protein to stabilise at surface of cell so in contact with membrane- glycoproteins
what does quatenary structure refer to
the way the polypeptides fit together when there is more than one polypeptide in a protein