Which of the following statements about hormones is correct? a. They tend to be large molecules. b. They exert their effects only on the same cells that produce them. c. They can exert strong effects only when they are present in high concentrations. d. They trigger a response by binding to target-cell receptors.

Verified step by step guidance

1. Step 1: Understand the question. The question is asking which statement about hormones is correct. Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions.
2. Step 2: Analyze each statement. Statement a suggests that hormones are large molecules. This is not necessarily true as hormones can be small molecules like adrenaline or larger molecules like insulin.
3. Step 3: Look at statement b. This statement suggests that hormones only affect the cells that produce them. This is incorrect as hormones are often produced in one part of the body (like the endocrine glands) and travel to affect cells in another part of the body.
4. Step 4: Consider statement c. This statement suggests that hormones can only have strong effects when present in high concentrations. This is also incorrect as hormones can have strong effects even at low concentrations.
5. Step 5: Finally, look at statement d. This statement suggests that hormones trigger a response by binding to target-cell receptors. This is correct. Hormones exert their effects by binding to specific receptors either on the surface of or inside their target cells.

Key Concepts

Hormone Structure

Hormones are signaling molecules that can vary in size and structure, including small molecules like steroids and larger proteins. While some hormones are indeed large, others are small and can easily diffuse through cell membranes. Understanding the diversity in hormone structure is essential for grasping their functions and mechanisms of action.

Target-Cell Specificity

Hormones exert their effects by binding to specific receptors on target cells, which are not necessarily the same cells that produce them. This means that hormones can influence various tissues and organs throughout the body, allowing for coordinated physiological responses. Recognizing this specificity is crucial for understanding how hormones regulate different biological processes.

Hormonal Concentration and Effect

The effects of hormones can vary significantly with their concentration in the bloodstream. While some hormones may require higher concentrations to elicit a strong response, others can be effective at very low levels. This concept highlights the importance of dosage and receptor sensitivity in hormonal signaling and physiological responses.