A researcher working with mammalian kidney cells grown in culture observed that cells treated with a proteolytic enzyme (an enzyme that breaks down proteins) lost the ability to respond to the hormone vasopressin but not to the hormone aldosterone.Which is a reasonable explanation for this observation?
A) The vasopressin receptor is a protein, whereas the aldosterone receptor is composed of either lipids or carbohydrates.
B) The cells lost the ability to synthesize the vasopressin receptor but retained the ability to synthesize the aldosterone receptor.
C) The vasopressin receptor is embedded in the cell membrane with an external portion that binds its ligand, whereas the aldosterone receptor is an intracellular receptor.
D) A debilitating mutation was introduced into the gene encoding the vasopressin receptor, but no such mutation affected the aldosterone receptor gene.
E) Vasopressin requires a receptor to stimulate a signal transduction pathway, whereas aldosterone can stimulate a signal transduction pathway without binding to a receptor.

Question

Quizplus · Accepted Answer

The observation suggests that the cells lost the ability to respond to vasopressin, which is a peptide hormone that binds to a receptor that is embedded in the cell membrane with an external portion that binds its ligand. This is different from aldosterone, which is a steroid hormone that can diffuse across the cell membrane and bind to an intracellular receptor. The cells treated with the proteolytic enzyme likely lost the ability to synthesize or maintain the vasopressin receptor, but retained the ability to synthesize the aldosterone receptor. Therefore, choice C is the most reasonable explanation.

A Researcher Working with Mammalian Kidney Cells Grown in Culture