Which of the following is NOT a function of proteins in biological systems?

Proteins play a pivotal role in numerous biological functions, but genetic coding is not one of them. The primary purpose of proteins is to perform various tasks that are critical for the survival and functioning of organisms.

Enzymatic activity is a major function of proteins, as they act as catalysts speeding up biochemical reactions without being consumed in the process. Cell signaling is another critical function where proteins, such as receptors and hormones, facilitate communication between cells, which is essential for coordinating biological processes. Additionally, proteins provide structural support to cells and tissues—for example, collagen in connective tissue or keratin in hair and nails.

In contrast, genetic coding is primarily the role of nucleic acids, specifically DNA and RNA. These molecules are responsible for the storage and transmission of genetic information. While proteins are produced based on the instructions encoded in genes, they do not themselves perform the function of genetic coding. Thus, recognizing that genetic coding is not a function of proteins clarifies why it is the correct choice in this context.