Cellulose is the most plentiful organic compound on our planet.
The purest natural form of cellulose is cotton, which is 90% cellulose.
The woody parts of trees are cellulose, as are the supporting materials
in plant stalks and leaves. All algae, except blue-green algae,
have cell walls of cellulose. (The name cellulose means "cell
sugar.") Although bacteria and animals generally do not depend
on cellulose for structural support, two kinds of bacteria and a
few marine invertebrates have a cellulose like polymer as an outer
Cellulose is a simple, straight-chain, b-1,4
polymer of glucose, with 300 to 3000 glucose units per molecule,
and a molecular weight of 50,000 to 500,000. The structure of one
strand of cellulose is shown on the right. These strands then are
bundled into fibrils and cross-linked by hydrogen bonds for strength.
The fibrils are twisted into bundles, and the bundles into strong
fibers that can be used for support.
As rope makers realize, fragile threads can gain great strength
if they are twisted into strands, the strands are twisted separately
into ropes, ropes into cables, and cables into hawsers. Nature anticipated
the human rope maker by several hundred million years.