Like others have said, it greatly depends on how deep, location, thickness, etc. of the scratches. There WILL be an effect, but whether or not this is noticeable depends on the factors combined. A deeper scratch will be noticeable, but several small ones might cause the auto-focus to struggle, while a thick faint one across the middle of the lens might show up as a smudge on all your pictures. Think of a small, thin thread. If you focus on it while it's close to your eyes, you'll see it. But if you don't move the thread and focus on something far away, chances are you won't see the thread anymore. Now add a bunch of threads and no matter what you do, you'll see them.
Also, unless the glass is somehow broken or a more serious issue is happening, the scratches should be on the protective glass for the camera, not the lens itself.