I think it best to think of the stories in the bible as allegories. Much like Jesus did in the New Testament to illustrate a point.

My view, is that the tree represents the ability for man to choose, unlike the animals, between good and evil. Thus the name is sometimes referred to as the "Tree of the knowledge of good and evil".

So the metaphoric "bite" of the fruit, is trying to paint a picture that god gave us the ability to choose, and that is what separates us from animals. The Garden of Eden is also figurative, that it represents the blissful ignorance of animals.