Researchers studying the rigidity and flexibility of the cell envelope used chemotaxis to measure the ability of microbes to squeeze through tight spaces. e. coli, a gram-negative bacterium, was able to traverse narrower channels than b. subtilis, a gram-positive microbe, even though both cells are the same size when grown without restriction. e. coli has the more flexible cell envelope becausea. lipopolysaccharide has no charge.
b. it has fewer flagella.
c. it has only a single membrane.
d. there is less structural carbohydrate.
e. there are fewer protein receptors.

D. there is less structural carbohydrate.

Explanation:

Most bacterial cells have a cell wall located outside the plasma membrane, formed by peptideoglycan or murein, which provides protection and shape to the cell. In addition to the wall, some bacteria have a polysaccharide capsule that surrounds this structure, this capsule is a carbohydrate envelope that can allow more or less flexibility to the bacterial cell. The more structural carbohydrates the polysaccharide capsule has the less flexible the bacteria will be. Thus, we can say that if E. coli has the most flexible cell envelope, compared to the envelope of other bacteria, it is because there is less structural carbohydrate in the E. coli envelope.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products