Megillah, Chapter One, Mishnah Five
From here until the end of the chapter there is a series of mishnayot in which each mishnah begins with the literary structure of there is no difference between x and y except, the literary structure that we saw in yesterdays mishnah. This type of structure is probably a result of the Mishnahs being an oral text. Halakhot phrased in this style are simply easier to remember.
1) There is no difference between Shabbat and Yom Tov except the preparation of food.
2) There is no difference between Shabbat and Yom HaKippurim except that the deliberate violation of the one is punished by a human court and the deliberate violation of the other by karet.
Section one: All work prohibited on Shabbat is also prohibited on Yom Tov, except work done in the preparation of food. For further reading on this subject look at the introduction to tractate Betzah.
Section two: An intentional transgression of Shabbat carries with it the death penalty, a punishment that is carried out by a human court. In contrast, an intentional transgression of Yom Kippur is not punished by a human court, but rather by karet, a punishment that is dished out by God.