Optometry Admission Test (OAT) Practice

Which of the following best describes steroids?

1. They are enzymes that aid digestion

2. They mimic the effects of neurotransmitters

3. They bind to hormone receptors and influence gene expression

4. They serve as secondary messengers in the cell

The correct answer is: They bind to hormone receptors and influence gene expression

Steroids are a class of organic compounds that include hormones such as cortisol, aldosterone, and sex hormones like estrogen and testosterone. The key characteristic of steroids is their ability to pass through cell membranes due to their lipid-soluble nature. Once inside the cell, they bind to specific hormone receptors, which then modulate gene expression by influencing the transcription of DNA into RNA. This process leads to changes in protein production and ultimately affects various physiological functions. This mechanism is fundamental to how steroid hormones operate, differentiating them from other types of molecules. For instance, enzymes are proteins that catalyze biochemical reactions but do not interact with gene expression directly in the same manner. Similarly, neurotransmitter mimics work primarily within the nervous system and do not engage the same pathways as steroids. Lastly, steroids do not serve as secondary messengers in the same way that other signaling molecules do, which typically relay signals from receptors to target molecules within the cell after a primary messenger has bound to the receptor. Thus, the role of steroids in binding to hormone receptors and influencing gene expression is the most accurate description of their function.