Question

Which of the following statements about steroid and nonsteroid hormones is false? a. Non-steroid hormones typically act through second messengers such as cAMP. b. Non-steroid hormones are not lipid soluble and cannot enter the target cell. c. Steroid hormones act usually slower than non-steroid hormones. d. Cortisol and aldosterone are non-steroid hormones that are produced by the cortex of the adrenal gland.

Short answer

Statement d is false.

Step-by-step solution

Understand the Differences

First, understand the basic differences between steroid and non-steroid hormones. Steroid hormones are lipid-soluble and can pass through cell membranes to directly influence the cell’s function. Non-steroid hormones, on the other hand, are not lipid-soluble and cannot pass through cell membranes. Instead, they bind to receptors on the surface of the cell and act through second messengers such as cAMP.

Evaluate Each Statement

Go through each provided statement and match it against known facts:- a. Non-steroid hormones typically act through second messengers such as cAMP.- b. Non-steroid hormones are not lipid soluble and cannot enter the target cell.- c. Steroid hormones act usually slower than non-steroid hormones.- d. Cortisol and aldosterone are non-steroid hormones that are produced by the cortex of the adrenal gland.

Analyze Statements a, b, and c

Statements a, b, and c are accurate based on our understanding of steroid and non-steroid hormones. Non-steroid hormones do act through second messengers (statement a), they are not lipid soluble and cannot enter the target cell (statement b), and steroid hormones typically act slower than non-steroid hormones (statement c).

Verify Statement d

Check the accuracy of statement d. Cortisol and aldosterone are actually steroid hormones. Therefore, the statement 'Cortisol and aldosterone are non-steroid hormones' is false.

Conclusion

Based on the analysis, statement d is the false statement.

Key concepts

hormone action

Hormones are like tiny messengers that travel through the bloodstream to reach various parts of the body. These chemical messengers work by binding to specific receptors on or inside target cells. Once they bind, they trigger a series of actions that affect the functioning of the cell. For example, hormones can change how genes are expressed, alter the metabolism of a cell, or modify how cells grow and divide.

There are two main types of hormones: steroid hormones and non-steroid hormones. Each type has a different mechanism for how it acts on target cells:

• Steroid hormones: These hormones are lipid-soluble, which means they can easily pass through the cell membrane. Once inside the cell, they typically bind to receptors in the cytoplasm or nucleus, directly influencing gene expression and protein synthesis.
• Non-steroid hormones: These are not lipid-soluble and cannot pass through the cell membrane. Instead, they bind to receptors on the cell surface, initiating a cascade of events inside the cell through second messengers like cAMP.

lipid solubility

The concept of lipid solubility is crucial to understanding how hormones interact with cells. Lipid solubility refers to a substance's ability to dissolve in fats, oils, and cell membranes.

Steroid hormones, being lipid-soluble, can easily pass through the lipid bilayer of the cell membrane. This allows them to enter the cell and bind to their receptors inside the cytoplasm or the nucleus. Examples of steroid hormones include cortisol, aldosterone, and estrogen.

On the other hand, non-steroid hormones are not lipid-soluble. This means they cannot pass through the cell membrane and must rely on binding to receptors on the cell surface. These hormones include insulin, growth hormone, and epinephrine. Their action depends primarily on second messengers because they cannot enter the cell directly.

second messengers

When a non-steroid hormone binds to a receptor on the cell's surface, it triggers a series of events inside the cell. These events usually involve second messengers like cAMP (cyclic adenosine monophosphate).

Second messengers are small molecules that carry out the message of the hormone inside the cell. They are crucial for amplifying the signal of the non-steroid hormone, ensuring that a small number of hormone molecules can have a large effect inside the cell. Common second messengers include:

• cAMP: Activated by enzymes like adenylate cyclase, cAMP can activate various cellular pathways, including those that regulate metabolism and gene expression.
• IP3 (Inositol trisphosphate): Helps in releasing calcium ions from intracellular stores, leading to various cellular responses.
• DAG (Diacylglycerol): Works alongside IP3 to activate protein kinase C, which in turn phosphorylates other proteins to alter their function.

Understanding these mechanisms helps clarify why non-steroid hormones rely on these intricate pathways to exert their effects.