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. Understand the basic structure and solubility of steroid hormones: Steroid hormones are derived from cholesterol, making them lipid-soluble. This characteristic allows them to easily cross cell membranes, which are also composed of lipid bilayers.
2. Compare the solubility of polypeptide and amino-acid-derived hormones: These hormones are generally not lipid-soluble. Instead, they are water-soluble, which means they cannot easily cross the lipid bilayer of cell membranes and typically bind to receptors on the cell surface.
3. Examine the mechanism of action for steroid hormones: Once inside the cell, steroid hormones bind to specific intracellular receptors. This hormone-receptor complex can then enter the nucleus and directly influence gene expression by acting on DNA.
4. Analyze the mechanism of action for polypeptide and amino-acid-derived hormones: These hormones bind to receptors on the cell surface, which triggers a cascade of intracellular signaling pathways. This often involves second messengers and can lead to signal amplification.
5. Evaluate the options given in the problem: Option a is correct because it accurately describes the lipid solubility and membrane-crossing ability of steroid hormones. Option b is incorrect because polypeptide and amino-acid-derived hormones do not necessarily have longer lifespans or greater signal amplification. Option c is incorrect because polypeptide hormones do not induce permanent changes. Option d is incorrect because steroid hormones do not bind to plasma membrane receptors; they bind to intracellular receptors.

Key Concepts

Steroid Hormones

Steroid hormones are lipid-soluble molecules derived from cholesterol. Their solubility allows them to easily cross cell membranes and bind to intracellular receptors, influencing gene expression directly. This characteristic differentiates them from other hormone types, which typically bind to cell surface receptors.

Polypeptide Hormones

Polypeptide hormones are composed of chains of amino acids and are generally water-soluble. They cannot cross the lipid bilayer of cell membranes, so they bind to receptors on the cell surface, triggering signal transduction pathways that amplify their effects. This mechanism allows for rapid and reversible changes in target cells.

Amino-Acid-Derived Hormones

Amino-acid-derived hormones are synthesized from single amino acids, such as tyrosine or tryptophan. They can be either water-soluble or lipid-soluble, affecting their mode of action. Water-soluble variants bind to cell surface receptors, while lipid-soluble ones can cross membranes to bind intracellularly, similar to steroid hormones.