How do steroid hormones differ from polypeptide hormones and most amino-acid-derived hormones? a. Steroid hormones are lipid soluble and cross plasma membranes readily. b. Polypeptide and amino-acid-derived hormones are longer lived in the bloodstream and thus exert greater signal amplification. c. Polypeptide hormones are the most structurally complex and induce permanent changes in target cells. d. Only steroid hormones bind to receptors in the plasma membrane.

Verified step by step guidance

1. Identify the key characteristics of steroid hormones: Steroid hormones are derived from cholesterol and are lipid-soluble, allowing them to easily pass through the lipid bilayer of cell membranes.
2. Understand the characteristics of polypeptide and amino-acid-derived hormones: These hormones are generally water-soluble and cannot pass through the lipid bilayer of cell membranes. Instead, they bind to receptors on the cell surface.
3. Analyze the options given: Option a states that steroid hormones are lipid soluble and can readily cross plasma membranes, which aligns with their key characteristics.
4. Evaluate the accuracy of other options: Options b, c, and d contain inaccuracies. Polypeptide and amino-acid-derived hormones are not necessarily longer-lived; they do not induce permanent changes in all cases; and it is incorrect that only steroid hormones bind to plasma membrane receptors as they generally bind to intracellular receptors.
5. Conclude the correct answer: Based on the analysis, option a is correct as it accurately describes the fundamental difference between steroid hormones and polypeptide/amino-acid-derived hormones.

Key Concepts

Hormone Classification

Hormones can be classified into three main categories: steroid hormones, polypeptide hormones, and amino-acid-derived hormones. Steroid hormones, derived from cholesterol, are lipid-soluble and can easily pass through cell membranes. In contrast, polypeptide and amino-acid-derived hormones are generally water-soluble and cannot cross the lipid bilayer, requiring receptor binding on the cell surface to exert their effects.

Mechanism of Action

Steroid hormones typically bind to intracellular receptors, leading to direct changes in gene expression and protein synthesis. This mechanism allows for long-lasting effects on target cells. Conversely, polypeptide and amino-acid-derived hormones bind to receptors on the cell membrane, triggering signal transduction pathways that amplify the signal and induce rapid cellular responses, but often do not alter gene expression directly.

Hormone Stability and Lifespan

The stability and lifespan of hormones in the bloodstream can vary significantly. Steroid hormones tend to have a longer half-life due to their lipid solubility, allowing them to remain active longer. In contrast, polypeptide and amino-acid-derived hormones are often more susceptible to degradation, leading to shorter durations of action and necessitating more frequent signaling for sustained physiological effects.