▁to ▁the ▁fact ▁that ▁water ▁mole cules ▁in ▁the ▁liquid - air ▁surface ▁of ▁al ve oli ▁are ▁more ▁attract ed ▁to ▁one ▁another ▁than ▁they ▁are ▁to ▁mole cules ▁in ▁the ▁air . ▁For ▁sphere - like ▁structures ▁like ▁al ve oli , ▁water ▁mole cules ▁line ▁the ▁inner ▁walls ▁of ▁the ▁air ▁sac s ▁and ▁stick ▁tight ly ▁together ▁through ▁hydro gen ▁b onds . ▁These ▁inter m ole cular ▁forces ▁put ▁great ▁rest raint ▁on ▁the ▁inner ▁walls ▁of ▁the ▁air ▁sac , ▁tight en ▁the ▁surface ▁all ▁together , ▁and ▁un y ield ing ▁to ▁stretch ▁for ▁in hal ation . ▁Thus , ▁without ▁something ▁to ▁alle vi ate ▁this ▁surface ▁t ension , ▁al ve oli ▁can ▁collapse ▁and ▁cannot ▁be ▁filled ▁up ▁again . ▁Sur fact ant ▁is ▁essential ▁mixture ▁that ▁is ▁released ▁into ▁the ▁air - f acing ▁surface ▁of ▁inner ▁walls ▁of ▁air ▁sac s ▁to ▁less en ▁the ▁strength ▁of ▁surface ▁t ension . ▁This ▁mixture ▁inser ts ▁itself ▁among ▁water ▁mole cules ▁and ▁breaks ▁up ▁hydro gen ▁b onds ▁that ▁hold ▁the ▁t ension . ▁Multiple ▁lung ▁dise ases , ▁like ▁I SD ▁or ▁R DS , ▁in ▁new born s ▁and ▁late - ons ets ▁cases ▁have ▁been ▁linked ▁to ▁d ys function ▁of ▁sur fact ant ▁met abol ism . ▁ ▁Sur fact ant ▁is ▁a ▁mixture ▁of ▁ 9 0 % ▁ph osph ol ip ids ▁and ▁ 1 0 % ▁other ▁prote ins , ▁produced ▁by ▁ep ith el