Wheat endosperm stores glutenin, the glutelin fraction that ranks among gluten’s major components. Its large polymeric subunits link through disulfide bonds into the elastic network that, together with gliadins, gives dough its strength and gas-holding power. High-molecular-weight glutenin subunits are the genetic markers breeders select for bread-making quality, since their pattern predicts loaf volume better than protein content alone. Too little glutenin gives slack, extensible doughs; the right balance gives structure. Flour millers blend wheats to hit the glutenin profile their bakery customers demand.