Subject: Where does the matter go in 'Mass Defect'?

The mass of an atom is different than the combined mass of its subatomic
particles.  The same is true about a molecules mass and its seperate atoms
combined mass(very small though).  I'm assuming this is an energy<-->mass
conversion.  The part I don't understand is if Carbon twelve has the exact same
subatomic particles(i.e. hadrons, mesons, etc.) as do the individual subatomic
particles themselves then what matter is lost in the transition to energy during
the formation of an atom from subatomic particles?  I can understand a single
particle converting to energy but not half of one?  Can the subatomic particles
shrink?  Is the gained/lost energy in the form of vibrations(heat)? Are photons
the matter that is being gained/lost?

Example:

Carbon twelve = 12 amu  

electron 0.000548579903amu x 6
proton   1.00727647amu     x 6
neutron  1.008664904amu    x 6

The sum of its subatomic particles however equal = 12.09893972amu

Re: Where does the matter go in 'Mass Defect'?