which parts of saturn 5 were jettisoned?

Answer 1

Technically, all of it. The Saturn 5 consisted of a three stage rocet system--and all three were jettisoned to get the Apollo spacraft on their way to the moon.

In addition, the Apollo also jettisoned the escape rocket assemply (that's the narrow spire at the very top)--those were useful as a safety measure, but only while the rocket was boosting into Earth orbit.

Most of the small remaining sections were also jettisoned--peice by peice, as they were no longer needed during the trip. The "descent" (lower section) stage of the Luner Excursion Module (LEM) was left on the moon, and the upper--ascent stage was left in lunar orbit. The Service Module was jettisoned just before they reached earth's atmosphere. Only the Command Module--that's the conical part where the astronauts were--actually returned to earth. If you see a picture of the whole Saturn 5 assembly--that's the little cone just under the spire of the escape rockets at the top.

Answer 2

during a normal procedure the interstage and the Escape tower were usually jettesioned around where the second stage falls off.

Answer 3

Read all about it

http://en.wikipedia.org/wiki/Saturn_V