Observing the molecular composition of galaxies
  The recent availability of wideband receivers and high sensitivity
instruments in the mm and submm wavelengths has opened the possibility of
studying in detail the chemistry of the interstellar medium in extragalactic
objects. Within the central few hundred parsec of galaxies, we find enormous
amounts of molecular material fueling a wide variety of highly energetic events
observed in starbursts (galaxies undergoing an intense burst of star formation)
and active galactic nuclei (AGN, where activity is driven by the accretion of
material onto the nuclear black hole).
  Here it is presented a brief summary of both the history and the latest
results in observational chemistry in distant galaxies. It will be shown how
the molecular emission, is a powerful tool to explore the physics of the
dust-enshrouded, buried nuclei of distant ultraluminous galaxies, which are
heavily obscured at other wavelengths. Special attention will be given to the
possibilities offered by next generationinstruments such as ALMA (Atacama Large
Millimeter Array), expected to have a vast impact on the field of Extragalactic
Chemistry. Molecular studies in the early Universe will become available at
unprecedented sensitivity and resolution.
