Biology / Unit 1 Bio 0196 short lesson, about 20 seconds
Polysaccharides: Cellulose and Chitin
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The idea
Cellulose and chitin are structural polysaccharides, giving rigidity to a plant's cell wall and an insect's exoskeleton, respectively.
In practice
Cellulose chains pack tightly enough to give a tree's cell walls strength; chitin gives a beetle's exoskeleton the same kind of rigidity.
Where people slip
Most animal digestive enzymes cannot break the bonds holding cellulose together, which is why fiber passes through the human gut largely intact.
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