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Introduction to Proteins
The Human Body (PY4010)
Kingston University
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PY4010Preview text
Amino acids:
-20 naturally occurring amino acids
-Share the same structure but different R group
-Have an amine group (basic) and Carboxylic acid group (acid)
-2 arrangements of 4 group around C to give L (levulo) or D (dextro) configurations but usually only L amino acids found in proteins.
-Different R sidechains confer different properties:
Negatively charged (acidic)
Positively charged (basic)
Polar (but uncharged and hydrophilic)
Non-polar (hydrophobic) Proteins linked via peptide bonds (O=C-NH) Peptide bonds have special properties- partial double bond between carbon and nitrogen. There is no rotation around this bond. Proteins are rigid because of the limited rotation around the peptide bonds. Peptide = chain of amino acids without structure Oligopeptide = small peptide Polypeptide = large peptide or protein Protein = polypeptide chain with structure Residue = amino acid in a peptide chain In a peptide, the amino acid with the free amine group is always written to the left, and COOH to the right. Primary structure = Sequence of amino acid residues in a polypeptide chain Secondary = Local structures of the polypeptide chain eg- alpha helix and beta-pleated sheet Tertiary = Compact shape held together by disulphide (covalent) bonds, ionic bonds and hydrogen bonds Quaternary structure = Combination of a number of polypeptides
ALPHA HELIX
Right-handed helix that coils clockwise. Usually, 3 amino acid residues per turn Formed and stabilised by H bonds, O in CO bonds to H of NH Formed by backbone of protein chain Adjacent chains can run parallel or antiparallel
BETA SHEET
Formed by backbone of protein chain Adjacent chains can run parallel or antiparallel Formed and stabilised by H bonds, O in CO bonds to H of NH
TERTIARY
Determines the shape of the protein molecule. Can form globular proteins, fibrous proteins and proteins that form filaments or tubes.
Disulphide bonds are covalent bonds.
Hydrophobic interactions contribute to protein folding, as hydrophobic side chains go into the centre of the protein and polar side chains stay on the outside to form hydrogen bonds with water.
Denaturation is caused by heat, acids and alkalis, organic solvents and mechanical force. Denaturation occurs when the proteins unfold.
Introduction to Proteins
Module: The Human Body (PY4010)
University: Kingston University
