Herbivores and Cellulose
Name: Richard D.
Monday, September 30, 2002
How do herbivores digest cellulose?
They do not. They have cellulose digesting organisms in their digestive
tract. The organisms get a source of food and shelter and the herbivores get
nutrients. This is an example of a mutualistic relationship-one in which
both organisms benefit.
They have an enzyme (a type of protein) that can bind to cellulose and break
it down. Our DNA does not encode this enzyme, so we do not make it. That is the
short answer. The longer version is that SOME herbivores, like cows, do not
make the enzyme either, but host a nice collection of microorganisms, that
live in their digestive tract, that DO make the enzyme. So the microorganisms
break down the cellulose, the cow gets the food value of the broken down
food, and the microorganisms get a nice warm, safe place to live: everybody
benefits. Termites do the same thing: they have a microorganism the lives in
the gut, that can break down cellulose.
Paul Mahoney, PhD
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Update: June 2012