Biological Systems MCAT Practice Exam

How do steroid hormones generally act on target cells?

1. By binding to cell surface receptors

2. By altering ion channel activity

3. By binding to intracellular receptors and altering transcription

4. By activating second messenger systems

The correct answer is: By binding to intracellular receptors and altering transcription

Steroid hormones primarily act on target cells by binding to intracellular receptors, which then alter gene transcription. This mechanism begins when a steroid hormone, a lipid-soluble molecule, diffuses through the cell membrane of the target cell due to its nonpolar nature. Once inside the cell, the hormone binds to a specific receptor located in the cytoplasm or nucleus. This hormone-receptor complex then translocates to the nucleus, where it can bind to specific DNA sequences and initiate or repress the transcription of target genes, ultimately leading to changes in protein synthesis. This direct interaction with DNA allows steroid hormones to exert long-term effects on cellular function and behavior, such as growth, metabolism, and reproductive processes. The influence of steroid hormones on gene expression is a fundamental aspect of their role in regulating various physiological processes throughout the body.