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 or
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.