Does the pope wear a silly hat! Of course they are poisonous. In fact, they are the most poisonous fruit in all of North America. The way you tell how poisonous an apple really is, is by looking at...
The seed of an apple is not poisonous but it might give a stomach ache.
Contrary to this, apple seeds do contain small amounts of cyanide, however, this is not enough to be poisonous by a long way.