The cells of your lungs express the same bitter taste receptor that is presence in the cells of your tongue (Deshpande et al., 2010). What's the reason for having these receptors in your lungs.
PZ Myers explains the concept of evolution by accident: Lungs with taste, or lungs with a fortuitous receptor?.
This is a very important concept and I'm delighted that PZ is promoting it. Adaptationists will not be happy. For more on this idea see: Evolution by Accident.
For more information about taste receptors see: Theme: A Sense of Smell/
Deshpande, D.A., Wang, W.C.H., McIlmoyle, E.L., Robinett, K.S., Schillinger, R.M., An, S,S,, Sham, J.S.K., Liggett, S.B. (2010) Bitter taste receptors on airway smooth muscle bronchodilate by localized calcium signaling and reverse obstruction. Nature Medicine. Published online October 24, 2010. [PubMed] [doi:10.1038/nm.2237]