Page 114 - Miracles Within the Molecule

Starch is fuel for metab o lism. Cellulose is a struc ture pecu liar to plants. The only thing
that dis tin guish es the two is the dif fer ence in their molec u lar bonds.

from these harsh envi ron ments, they need a very sound cell wall. For
that rea son, there are pack aged cel lu lose groups in all plant cells. 50
Despite being a pol y sac cha ride, a sugar mol e cule like starch, cel lu -
lose can not be digest ed by human beings. That is because the glu cose
units in cel lu lose are attached to one anoth er with gly co side bonds.
Mammals' diges tive tracts have no enzyme able to break down this
bond. That's why that cel lu lose is not a source of food for us. Cellulose
can, how e ver, be digest ed by rumi nants, because in their diges tive
tracts, these ani mals host micro or gan isms that secrete cel lu lose
enzymes. By means of these enzymes, rumi nants can break down the
cel lu lose they eat with out dif fi cul ty and turn it into a form of food and
ener gy. 51

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