Amino acids

Amino acids are the basic structure units of proteins. An alpha-amino acids consists of an amino group,a carboxyl group,a hydrogen atom, and a distinctive R group, all of which are bond to an alpha carbon atom. This carbon atom is named alpha because it is adjacent to the carboxyl( acidic) group.An R group is referred to as a side chain for reason that will be evident shortly.

Amino acids consist of an asymmetric carbon bonded to 4 different covalent partners:

Different amino acids differ in their R-group.
R-group determines physical and chemical characteristics of a particular amino acid. R-groups can be nonpolar, polar, or electrically charged (i.e. ionic).
Amino acids can be covalently linked through condensation reactions to form polymers. This covalent linkage is called a peptide bond.

All polypeptide chains have a polarity: N-terminus and carboxy-terminus.
Polypeptides have common backbone of -N-C-C-N-C-C-N-C-C-(N-C-C)n-
Polypeptides range in size from a few to 1000's of monomers.
Unlimited number of polypeptides can be made by varying the number and the order of amino acids in the chain.
Protein function depends on its 3 dimensional shape (i.e. its conformation).
the sequence of amino acids along a polypeptide chain determines the conformation of the protein.
correct 3-D folding of polypeptide determines the function of a protein. This is because often protein function depends on recognition and binding of other molecules (binding like a lock and key)