Are Put options still valid if a company goes bankrupt? like GM or any bank?

Does anyone know if Puts are still valid and you can collect if a company goes bankrupt and the stock goes to zero? Do you have to collect from the person who sold you the Put or was the money already allocated when you bought the Put? For instance if you buy a GM put at 2 or 3 and GM goes bankrupt and stock goes to zero can you still excise the Put and buy GM at 2 or 3 and make money that way or cut your losses that way - if you buy GM at 4?

Thanks,
Jon

Yes, puts are still valid.