Depends on the car, most modern cars... no. Not one way that I am aware of... most of the keys now have a "transponder" (RFID Chip) that the car needs to see before it will start... or stay running. This security measure should not be bypassed, not only could you possibly completely disable your car (umm... forever !), but you could potentially hurt yourself (ignition areas can give you quite a shock!) , and you would also seriously degrade the car's value because its security has been bypassed.
My advise:
Go to the dealer, pay the obscene amount of money, and have them make you another key. (30-100 bucks)
Oh and don't forget your proof of ownership.
Matty-