Summary of the PP Chain

Reaction Energy Released Reaction Timescale
H + H D + e⁺ + neutrino
e⁺ + e^- photon 0.16 Mev
1.02 Mev 14 billion yrs
a few seconds
H + D ³He + photon 5.49 Mev 6 seconds

³He + ³He ⁴He +H +H 12.86 Mev 10⁶ years

You should convince yourself, like we did in class, that the origin of antimatter in the first step (e.g. the positron) must occur to satisfy the rules of conservation of baryon #, lepton #, and charge.
The total energy released is
2(0.16 + 1.02 + 5.49) + 12.86 = 26.20 Mev
The mass difference between 4 protons and 1 ⁴He nucleus is 0.0287 amu which yields 26.73 MeV.
Where is the missing 0.53 Mev its carried off by the neutrinos (0.265 Mev each time).
When the density of H and He become comparable in the core, the PP reaction changes to favor the production of Be, Li, and B.
These reaction chains are shown below:

The decay of B(oron) into Be(rrylium) emits a neutrino of energy 7.2 Mev, much higher than the neutrinos emitted by the first step of the PP chain.
In principle, if we had good neutrino telescopes (which we don't, for obvious reasons), measuring the ratio of 7.2 Mev neutrinos to 0.26 Mev neutrinos would yield the age of a stellar core.
Note: You might be wondering about Berrylium and Boron since they, in fact, are elements not produced by fusion (but simply intermediate fusion products). These elements, as well as some other isotopes are produce by a process known as spallation which involves in interaction of light element nuclei with cosmic rays (very high energy protons of unknown origin). See This Wiki Entry