1) Almost all amino acids are chiral. The body only uses L amino acids, and proteins are chains of amino acids that in the most simple sense fold up into a single structure by themselves when they are formed. Do you think a cell could live with all D (the opposite of L) amino acids, explain your logic. When I ask 'live', I mean could the organism/cell be composed completely of D amino acids and live 

2) When an amino acid's side chain, such as aspartic acid, has a pKa, that pKa is not the same if the amino acid occurs on the interior of a protein. Why would the pKa of a side chain of an Asp occuring on the inside of a protein be different from an Asp on the outside of a protein? 

Please provide web references.