Proteins, nucleic acids, and carbohydrates are grouped by common structural features found within their group. Lipids can be grouped based on: their high solubility in nonpolar solvents.

In general, lipids are molecules of low water solubility, so they can be classified as low polar. In general, lipids are molecules of low water solubility, so they can be classified as nonpolar.

The lipids belong to a group of heterogeneous substances, from the structural point of view as in the functions they fulfill in the cells. All lipids have in common that they are unctuous to the touch, very poorly soluble in water and soluble in apolar solvents, such as ether, chloroform, or benzene. These solvents are those used to extract them from cells or tissues.

Explanation:

Lipids are biomolecules that are identified as being poorly soluble in water and very soluble in non-polar organic solvents. Although lipids are chemically heterogeneous, they all have a common denominator with respect to their structure: a part of their molecule is of hydrocarbon characteristic, and therefore is apolar. This structural characteristic is responsible for water insolubility and solubility in non-polar solvents.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.