The sketch shows a fragment of cellulose. It is also a very long polymer of
glucose. There are roughly 4,000 to 8,000 glucose molecules strung
together.
The glucose units are sketched as a stair step to get the beta OH
of one near the #4 OH of another. The molecule never has branches. The only
difference from linear starch is beta-1-4 links instead of alpha-1-4 links, but
it makes a world of difference in properties. Cellulose is very strong. Its
links are broken by cellulase enzymes that are far less common in nature than
are the amylase enzymes that split starch. Cellulose confers strength and
structure to plants, and it would be bad if there were a plethora of organisms
in nature that could break down cellulose. Cellulose is found as a composite
mixture with hemicellulose
and lignin.
Two glucose molecules reacted with a beta-1-4 link make the disaccharide cellobiose. It is an important intermediate in the enzymatic hydrolysis of cellulose.
The sketch of linear starch has many glucoses strung together with alpha-1-4 linkages. It would take dozens of sheets of paper to show a typical starch molecule at the scale of this sketch. Starch can be mostly linear, mostly branched, or a mixture depending on its source. A fragment of branched starch is shown in another sketch. There can be branches on the branches and several branches on any stem. The proportions of linear and branched and the degree of branching cause starch from different sources to have different properties.