40. Most of the carbon dioxide in the blood of humans is transported
(A) as dissolved CO2 in plasma.
(B)as bicarbonate ion in plasma.
(C)attached to hemoglobin in red blood cells.
(D)attached to hemoglobin in plasma.
(E) as carbonic acid.

36. What is the role of calcium in muscle contractions? (A) to break the cross-bridges as a cofactor in the hydrolysis of ATP (B)to spread the action potential through the T-tubules (C)to transmit the action potential across the neuromuscular junction (D)to bind with troponin, changing its shape so that binding sites on the actin filament are exposed (E) to re-establish the polarization of the plasma's membrane following an action potential

37. The glandular secretions involved in digestion that would most likely be released as inactive precursors are (A) protein-digesting enzymes (B)fat-solubilizing bile salts (C)acid-neutralizing bicarbonate (D)carbohydrate-digesting enzymes (E) nucleases

38. Newborn humans face thermoregulatory challenges as do small mammals. One mechanism they use to generate heat is (A) shivering thermogenesis in "brown fat." (B)nonshivering thermogenesis in "brown fat." (C)convection in "brown fat." (D)evaporation in "brown fat." (E) radiation in "brown fat."

39. The "hematocrit" is a measure of which blood constituent or index? (A) blood clotting time (B)leukocytes number (C)erythrocytes volume (D)blood oxygen saturation rate (E) plasma volume

41. What is the correct rank order for relative toxicity (most to least) of the primary nitrogenous wastes used by different animals? (A) ammonia > urea > uric acid (B)uric acid > ammonia > urea (C)urea > uric acid > ammonia (D)ammonia > uric acid > urea (E) urea > ammonia > uric acid

42. Parathyroid hormone's main function is to (A) increase glucose mobilization during stress or fasting. (B)increase calcium by mobilizing the ion from bone. (C)increase sodium through reabsorption from kidney. (D)increase basal metabolic rate. (E) antogonized with thyroid hormone in various functions.

43. Fertilization of an ovum of human normally occurs in the (A) uterus. (B)ovary. (C)oviduct. (D)vagina (E) cervix.

44. In mammals, the melanocytes ultimately arise from (A) the endoderm. (B)the mesoderm. (C)the ectoderm. (D)the notochord. ((E) the neural tube.

45. To infect a cell, HIV must (A) kill cytotoxic T cells and bind CD4. (B)bind both CD8 and a cytokine co-receptor. (C)bind both CD8 and a class I MHC protein. (D)bind both CD4 and a cytokine co-receptor. (E) bind CD4 and kill macrophage.

46. In animals, the chemicals used to attract mates are called (A) hormones. (B)allomones. (C)pheromones. (D)allelopaths. (E) genetic byproducts.