Subject: What is the use of optically active compounds?

I'm analyzing optically active compounds for a science project (okay, 
I know you don't want questions concerning ideas for projects so I 
made my question a bit more specific) 
I have the plans for building a polarimeter from an article in 
'Scientific American' (about 1986) and it also says:
This phenomenon (optical activity) also has practical applications, 
such as the concentration of sugar in food products and sugar 
refining. How exactly does optical activity affect the concentration 
of sugar? Any ideas for other practical applications?
Also, do you know of any other optically activecompounds that I can 
analyze (other than compounds containing sugar)?
One last question, What exactly does an optically active compound 
have that makes it optically active?
The proposal is due in 9 days, so please reply ASAP, ok?
Thanks

Re: What is the use of optically active compounds?