Which of the following define the stereochemistry of alanine (as per the structure shown)? Note: Functional groups arranged horizontally are facing towards the front, and the functional groups arranged vertically are facing towards the back. H,N- S- OF COOH CH, O d- OR- H

stereochemistry can be defined as the arrangement of functional groups on the alpha carbon atom with respect to  carboxyl and amino groups. 
This arrangement gives the two types of sterioisomers of amino acids which are D amino acids and L amino acids.

Amino acids are connected together by peptide bonds to form protein macro molecules. Most of the amino acids are L isomers.