Problem 5 - Campbell Biology

Question

\(\begin{equation} \begin{array}{l}{\text { What do steroid and peptide hormones typically have in }} \\ {\text { common? }} \\ {\text { (A) their solubility in cell membranes }} \\ {\text { (B) their requirement for travel through the bloodstream }} \\ {\text { (C) the location of their receptors }} \\ {\text { (D) their reliance on signal transduction in the cell }}\end{array} \end{equation}\)

Step-by-Step Solution

Answer

The correct answer is (B) their requirement for travel through the bloodstream.

Step 1: Understand Hormones

Review the differences between steroid hormones, which are lipid-soluble and can easily pass through cell membranes, and peptide hormones, which are not lipid-soluble and cannot pass through cell membranes as easily.

Step 2: Analyze Solubility in Cell Membranes

Compare the solubility of steroid hormones and peptide hormones in cell membranes. Steroid hormones are lipid-soluble while peptide hormones are not. Thus, they differ in their solubility in cell membranes.

Step 3: Requirement for Travel Through the Bloodstream

Both steroid and peptide hormones travel through the bloodstream to reach their target cells. Hence, this characteristic is common to both types of hormones.

Step 4: Location of Receptors

Steroid hormones typically have intracellular receptors because they can cross cell membranes, while peptide hormones have receptors on the cell surface because they cannot cross the membranes. Therefore, the location of their receptors is different.

Step 5: Reliance on Signal Transduction

Peptide hormones rely heavily on signal transduction mechanisms to relay their messages inside the cell. Steroid hormones, on the other hand, generally do not rely on signal transduction in these pathways since they can directly influence gene expression. So, this reliance on signal transduction is different for both types.

Step 6: Select the Correct Answer

From the analysis, it is clear that both steroid and peptide hormones require travel through the bloodstream (B).

Key Concepts

Steroid Hormones

Steroid hormones are a type of hormone derived from cholesterol. They are lipid-soluble, meaning they can easily dissolve in fats and oils. Because of this property, they can pass through cell membranes, which are made of lipid bilayers. Once inside the cell, steroid hormones bind to intracellular receptors, usually found in the cytoplasm or nucleus. This binding typically influences gene expression directly, by either promoting or inhibiting the transcription of specific genes. In simpler terms, steroid hormones can enter the cell and directly change how genes are read and proteins are made.

Peptide Hormones

Peptide hormones are made up of amino acids and are water-soluble. Unlike steroid hormones, they cannot easily pass through the lipid bilayer of cell membranes. Instead, they bind to receptors located on the cell's surface. These receptors are often proteins that extend through the cell membrane, allowing the peptide hormone to attach on the outside of the cell. Once this binding occurs, the signal needs to be relayed inside the cell through signal transduction mechanisms. Peptide hormones often act quickly because they trigger a cascade of signals inside the cell to produce a rapid response.

Signal Transduction

Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events. For peptide hormones, this usually involves binding to a receptor on the cell surface. This binding activates a signal transduction pathway, often involving second messengers like cAMP (cyclic adenosine monophosphate). These second messengers then activate other proteins inside the cell, leading to a chain reaction that eventually results in a cellular response. Signal transduction allows the cell to amplify a small signal and produce a significant biological effect. Steroid hormones generally do not require signal transduction because they act directly inside the cell.

Hormone Receptors

Hormone receptors are specific proteins that bind to hormones. These receptors can be located either on the cell surface or inside the cell. For steroid hormones, receptors are typically found inside the cell because these hormones can cross cell membranes. Once bound, the steroid hormone-receptor complex can move into the nucleus and directly affect gene expression.
Peptide hormones, on the other hand, bind to receptors on the cell surface. These surface receptors then activate signal transduction pathways to relay the message inside the cell. The location and type of receptor involved is crucial in determining how the hormone will affect the target cell.
Lastly, it's important to note that both types of hormones use their respective receptors to achieve specific and often rapid physiological responses.