It's the carbon dioxide trapped by the dough that makes the air cells in the bread expand when heated, hence making it rise.
(It; 's; the carbon dioxide trapped by the dough) (the carbon dioxide; trapped; by the dough) (the dough; makes; the air cells in the bread expand when heated) Context(the dough makes,List([35, 55))):(the air cells in the bread; expand; T:when heated)
the dough makes,List([35, 55))
It the carbon dioxide the dough the air cells in the bread
's trapped makes expand
the carbon dioxide trapped by the dough
by the dough
the air cells in the bread expand when heated
T:when heated