My cat meows at me at 5:00 AM every morning!?

I don't know what her problem is, but my youngest cat will sit and meow at us every morning at 5:00 AM! It's liek clockwork! I know she just wants us to get up (because when we do so, she shuts up) but is there anything we can do to get her to stop??? I don't have to get up until 6:00AM and it's really frustrating! And we can't close our bedroom door because she'll sit and scratch at it!!