AEMCA Practice Exam

In what way do amino acid hormones operate in the second messenger system?

1. They directly enter the cell to regulate gene expression.

2. They attach to cell membranes to activate enzymes.

3. They are rapidly destroyed by enzymes in the bloodstream.

4. They bind only to target organs.

The correct answer is: They attach to cell membranes to activate enzymes.

Amino acid hormones, particularly those that are water-soluble, operate in the second messenger system by binding to cell membrane receptors. When these hormones attach to specific receptor sites on the surface of target cells, they trigger a series of biochemical events inside the cell. This process often involves the activation of enzymes and the production of second messengers, such as cyclic AMP (cAMP). These second messengers amplify the signal, leading to various physiological responses, such as changes in enzyme activity, ion channel permeability, and ultimately cellular responses. The first option suggests that these hormones enter the cell directly to regulate gene expression, which is more characteristic of steroid hormones, not amino acid hormones. The third option states that they are rapidly destroyed by enzymes in the bloodstream; while it's true that some hormones can be degraded quickly, this does not describe how amino acid hormones function in the context of signal transduction. The fourth statement claims that they bind only to target organs, which is misleading as it implies a limitation to their function, whereas these hormones can act on target cells throughout the body by binding to specific receptors. Understanding the operation of amino acid hormones within the second messenger system emphasizes their reliance on membrane receptors and intracellular signaling pathways to exert their effects rather than direct entry