AP Biology: Endocrine Signaling Practice Questions
Test yourself on AP Biology: Endocrine Signaling with 12 original AP Exams practice questions. Pick an answer to see instant feedback and a full explanation.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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1. Which statement best describes endocrine signaling in animals?
Explanation. Endocrine cells secrete hormones into blood or other body fluids. Target cells respond only if they have the appropriate receptors, even when those cells are far from the hormone source.
2. Why do only some cells respond to a circulating hormone?
Explanation. A hormone may travel broadly, but response depends on receptor expression. Cells without the matching receptor do not detect that hormone's signal.
3. A steroid hormone diffuses through a cell membrane and binds an intracellular receptor. What is a common result of this pathway?
Explanation. Steroid hormones are lipid-soluble and often bind receptors in the cytoplasm or nucleus. The hormone-receptor complex can influence transcription by binding regulatory DNA sequences or transcriptional machinery.
4. Why do many peptide hormones bind receptors on the cell surface instead of entering the cytoplasm directly?
Explanation. Peptide hormones are usually water-soluble. They bind membrane receptors, which then activate intracellular signaling pathways such as kinase cascades or second-messenger systems.
5. A receptor activates adenylyl cyclase, which increases cyclic AMP levels. In this pathway, cyclic AMP is best described as what?
Explanation. Cyclic AMP is a second messenger. It is produced inside the cell after receptor activation and can activate downstream proteins, amplifying the original signal.
6. Which feature helps signal transduction pathways amplify endocrine signals?
Explanation. Amplification occurs because each step can activate multiple molecules at the next step. This allows a low concentration of hormone to produce a large cellular response.
7. After blood glucose rises, insulin release helps lower blood glucose. Which regulatory pattern is this?
Explanation. Insulin secretion after high blood glucose is part of a negative feedback loop. The response promotes glucose uptake and storage, moving glucose levels back toward a regulated range.
8. Which comparison between insulin and glucagon is most accurate?
Explanation. Insulin and glucagon have opposing roles in blood glucose regulation. Insulin promotes glucose uptake and storage, while glucagon promotes release of stored glucose when blood glucose is low.
9. What is a likely consequence if target cells lose functional insulin receptors?
Explanation. Hormone response requires receptor binding and downstream signaling. If insulin receptors are not functional, target cells cannot respond normally to insulin.
10. In the hypothalamus-pituitary-target gland axis, why are multiple hormone steps useful?
Explanation. Endocrine axes can coordinate signals among the hypothalamus, pituitary, and target glands. Multiple steps allow regulation, amplification, and feedback at several points.
11. A high level of a thyroid hormone reduces release of upstream hypothalamic and pituitary hormones. What does this illustrate?
Explanation. When a downstream hormone inhibits upstream releasing or tropic hormones, the system uses negative feedback. This helps keep hormone levels within a functional range.
12. Which experimental result would best support the claim that a hormone uses a membrane receptor and second messenger pathway?
Explanation. A rapid increase in an intracellular messenger after hormone exposure supports a membrane receptor pathway. Receptor expression links the external hormone signal to internal transduction.
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FAQ
What endocrine signaling ideas are high yield for AP Biology?
Focus on hormones, target-cell receptors, steroid versus peptide hormone pathways, second messengers, signal amplification, negative feedback, and endocrine axes.
How do steroid and peptide hormones differ in signaling?
Steroid hormones are lipid-soluble and often bind intracellular receptors that regulate gene expression. Peptide hormones usually bind membrane receptors and activate intracellular signal transduction.
Why is feedback important in endocrine systems?
Feedback keeps regulated variables such as blood glucose or hormone concentration within functional ranges. Negative feedback is especially common because it opposes deviations from a set range.