I am making white wine and I am asked to add metabisulfite--but I do not have any is chitosan the same thing? I am new at this.:)

Nope.
Sodium Metabisulphite is used to cease fermentation to keep residual sweetness in the wine.
It's also used as a preservative and cleanser.

More info here: Campden tablets - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Campden_tablets)