A small molecule binds to a G protein, preventing its activation. What direct effect will this have on signaling that involves cAMP?

Correct Answer: B

Rationale: G proteins activate adenylyl cyclase in cAMP signaling, converting ATP to cAMP to amplify signals (e.g., epinephrine response). Blocking G protein prevents this activation, halting cAMP production. Hormone binding occurs upstream, excessive cAMP or phosphorylation would require activation. This inhibition distinguishes the direct effect, key to understanding second messenger disruptions in cellular signaling pathways.

Correct Answer: C

Rationale: Gonads (ovaries, testes) produce steroid hormones estrogens, progesterone, testosterone from cholesterol, acting intracellularly to regulate reproduction. Amine hormones (e.g., thyroid) derive from tyrosine, peptides (e.g., insulin) from amino acids, and catecholamines (e.g., epinephrine) from adrenal medulla. Steroid's lipid-based nature distinguishes gonadal output, critical for sexual development, contrasting with other chemical classes.

Correct Answer: A

Rationale: The anterior pituitary arises from oral ectoderm, specifically Rathke's pouch, during embryogenesis, forming hormone-secreting cells. Neural ectoderm forms the nervous system (including posterior pituitary), mesoderm muscles/bones, and endoderm digestive organs. Oral ectoderm origin distinguishes anterior pituitary development, key to its endocrine role, contrasting with neural or internal layer derivatives.

Correct Answer: D

Rationale: Directing blood flow is a circulatory system function, adjusting tissue perfusion via vessels to maintain homeostasis, not an endocrine role. The endocrine system regulates immunity (e.g., cortisol affects immune cells), reproduction (e.g., FSH, LH drive gonadal function), and heart rate/blood pressure (e.g., epinephrine increases both), using hormones like adrenaline or aldosterone. Water balance, another endocrine task (e.g., ADH), was replaced here to fit four options, but blood flow direction relies on vascular dynamics, not glandular secretion. This distinction highlights endocrine's chemical signaling versus circulatory mechanics, key to system roles.

Correct Answer: B

Rationale: Hyperparathyroidism involves excess parathyroid hormone (PTH), raising serum calcium by mobilizing it from bones and increasing kidney reabsorption, while lowering phosphorus both are abnormal. Sodium, chloride, and potassium aren't directly PTH-regulated; aldosterone or ADH affect them. The question's 'select all' (calcium, phosphorus) is adapted here to single-answer (calcium), as it's the hallmark. Calcium's elevation distinguishes hyperparathyroidism, key to its pathology (e.g., kidney stones), unlike unaffected electrolytes.