This actually happened at Harvard University in October of 1997.

In a biology class, the prof. Was discussing the high glucose
levels foundin semen.

A young female (freshman) raised her hand and asked,
"If I understand, you're saying there is a lot of glucose, as
in sugar, in male semen?"

"That's correct." responded the prof, going on to add statistical
info.

Raising her hand again, the girl asked,
"Then why doesn't it taste sweet?"

After a stunned silence, the whole class burst out laughing, the
poor girl's face turned bright red, and as she realized exactly what
she had inadvertently said (or rather implied) she picked her books
up without a word and walked out of class... and never returned.
However, as she was going out the door, the prof's reply was
classic!

Totally straight-faced he answered her question,
"It doesn't taste sweet because the taste buds for sweetness
are on the tip of your tongue and not the back of your throat.