Why is the amino acid glycine non polar?

I'm guessing a bit here.

I believe they're talking about the side chains of the amino acids when they rate them as polar or non-polar. Since glycine has no side chains:

NH2 - CH2 - COOH

It is classified as non-polar.

I think there is actually some polarity but the electronegativity of the nitrogen counteracts some of the electronegativity of the oxygens and you're left with a "fairly non-polar" molecule (how's that for dodging the question?).

This probably isn't the answer you hoped for. Maybe some other genius can shed more light on this.

Perito your right.

Glycine isn't non polar when considred as a single molecule, however it is callsed as a non polar amino acid when considering it's inclusion in a polypeptide or protein structure. This is indeed because of it's lack of side chain.

See this venn diagram for the amino acids classifications according to side chains:

http://apodtele.googlepages.com/aa_venn_diagram.jpg

This is very useful information when trying to understand protein structure and function.