Both insulin and somatostatin:

Correct Answer: C

Rationale: Insulin and somatostatin both inhibit glucagon release from A cells. Insulin has disulfide bonds, somatostatin does not; only insulin causes K^+ uptake.

Correct Answer: C

Rationale: Glucose uses Na^+-dependent SGLT1 for luminal uptake; fructose uses GLUT5 (Na^+-independent). Absorption is mainly in the jejunum.

Correct Answer: D

Rationale: Osteoclasts originate from monocyte/macrophage lineage in bone marrow.

Correct Answer: C

Rationale: The pancreas acts as an endocrine gland, secreting insulin directly into the bloodstream, and an exocrine gland, secreting digestive enzymes through ducts.

Correct Answer: D

Rationale: Parathormone, or parathyroid hormone, is produced and secreted by the parathyroid glands. Low calcium levels will stimulate release of parathyroid hormone, which increases the plasma level of calcium. Parathormone acts on the renal tubules to increase the excretion of phosphorus in the urine and to stimulate the reabsorption of calcium. Parathormone also acts on bone, causing the release of calcium from the bone into the bloodstream.