A college professor explains to his class that sperm has a lot of glucose as that is what it gives it the energy.

A girl raises hand and asks "glucose is in sugar, right?"

Professor says "that's correct."

The girl then asks "so why doesn't it taste sweet?" She then realizes what she said, gets all red and picks up her books to leave the class.

As she is leaving the professor answers with a totally straight face, "That is because the taste buds for sweetness are on the tip of your tongue not the back of your throat."