Proteins play key roles in olfaction. One kind of protein, called , attaches itself to hydrophobic odorant molecules so that they may dissolve in watery mucous. A second class of proteins, to which odorant molecules become bound and initiate transduction, are coded by the largest family of genes in mammals and are called . Group of answer choices

The correct answer is "Odorant-binding proteins (OBPs); Olfactory receptors (ORs)".

Explanation:

Odorant-binding proteins (OBPs) are low-molecular soluble molecules that are secreted in high amounts in the nasal mucus layer. The precise biological activity of OBPs remains unclear, however, its solubility and ability to attach to hydrophobic odorant molecules suggest that they acts as carriers. A second class of proteins called olfactory receptors (ORs), act at the genetic level by initiating transduction once odorant molecules attach to them. ORs are coded by the largest family of genes, which include more than 100 genes and pseudogenes that represent around 3% of the genome.

the answer is d p: cell, q: organ, r: organ system, s: tissue