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STRUCTURE AND FUNCTION OF PROTEINS - Coggle Diagram
STRUCTURE AND FUNCTION OF PROTEINS
amino acids are the building blocks of proteins they contain carboxyl group COOH, R group, and AMINE group as well as H atom.
there are 20 different amino acids due to there being 20 different types of R groups
two isomeric forms L(levulo) and D(dextro) around central C but usually only L found in proteins.
different R side chains confer different properties e.g can be negatively charged(acidic) positively charged (basic) polar but uncharged(hydrophilic) non-polar but charged (hydrophobic)
PROTEINS FORM PEPTIDE BONDS BETWEEN THE COOH AND NH2 groups to form
rigidity around CONH peptide unit
peptide- chain of amino acids with structure
oligopeptide- small peptide
polypeptide- large peptide
residue- amino acid in a peptide chain
primary sequence- sequence of amino acid residue in a peptide chain
secondary- local structure of polypeptide chain due to hydrogen bonds e.g a-helix B-pleated sheets
tertiary- due to bending and twisting of secondary amino acid chains to be more compact form( ionic bonds, disulphide bonds, hydrogen bonds)
quartenary- the combination of a number of different polypeptide
a helix- 3.6 amino acid residues per turn
side chains face outwards formed by the backbone of the amino acid
beta sheet- also formed by the backbone of amino acid, sheet like structure side chains extend above and below sheet
tertiary and quarternary structures of proteins determine, the shape of proteins
Globular proteins: Myoglobin,
Haemoglobin, Cytochrome c, Insulin,
most enzymes (e.g. Lysozyme
Fibrous proteins: Collagen, Elastin, -keratin
Proteins that form filaments or tubes:
Actin, Tubulin
forces in bonds important for determining protein tertiary and quarternary structure
.Covalent bonds: disulphide bonds: strong
Ionic bonds: weak in water
Hydrogen bonds: weak
Van der Waals attractions: very weak
functions of proteins-
Digestion: carbohydrates, fats, proteins
• Structural- e.g. collagen
• Blood clotting: fibrin clot catalysed by thrombin
•Defence-immune system-antibodies and
complement
•Movement: muscle actomyosin is an ATPase
•Nerve conduction:ion pumps for Na+, Ca++
•Hormone signalling
Denaturing of proteins caused by heat, acid and alkali, mechanical force, organic solvents.
mutation underlies inherited diseases e.g
Cystic fibrosis Chloride channel
Phenylketonuria Phenylalanine hydroxylase
Sickle cell anaemia Beta globin of haemoglobin
(Glu to Val mutation). 6th residue
of the beta chain
(alpha chains in yellow,
beta chains in blue)
Mutation produces a sticky
path causing deoxy Hb to
form insoluble aggregates
that distort red blood cells
to the characteristic sickle
shape. Such cells are fragile,
lyse easily, giving rise to
anaemia.
