A dipeptide is when 2 amino acids are joined together
Proteins are made up of one or more amino acid polypeptide chains
Amino acids
Structure is:
The R represents a variable group, the
COOH is a carboxylic acid group, and the
NH2, the amino group
Condensation reactions
Amino acids are linked by condensation reactions to form a polypeptide chain, and a molecule of water
The bonds formed are called PEPTIDE BONDS
The reverse reactions are called HYDROLYSIS reactions, and
this is what happens in digestion
Protein structure
Primary structure: sequence of amino acids in the chain
Secondary structure: the polypeptide chain doesn't remain flat and straight.
Hydrogen bonds form between amino acids in a chain. These make it coil into and Alpha helix or a Beta pleated sheet
Tertiary: The coiled or folded chain of amino acids is often
coiled or folded further. More bonds form between different
parts of the chain
For protein made from a single polypeptide chain, the
tertiary structure forms their final 3-D structure
Quaternary Structure: consists of proteins made of several different polypeptide chains held together by bonds.
It is the way the chains are assembled together that make up the forth level of structure
For proteins made of more than one polypeptide chain, this is their final structure
Protein Function
Enzymes are roughly spherical in shape due to the tight
folding of the polypeptide chains (tertiary structure)They're
soluble and often have roles in metabolism. Others help
synthesize large molecules
Antibodies are involved in the immune response.
They're made of two light polypeptide chains and two
heavy polypeptide chains. They have variable regions-
the amino acid sequences in this region vary greatly
Transport proteins are present in cell membranes. They
contain hydrophobic amino acids which cause the protein to
fold up and form a channel. They transport molecules and ions
across the cell membrane
Structural proteins are physically strong. they consist
pf long polypeptide chains parallel to each other with
cross links between them. For example- keratin and
collagen