45. Which of the following is a second messenger? (A) Diacylglycerol (B) Adenylyl cyclase (C) Phospholipase C (D) ATP

48. Which statement best explains why pentose phosphate pathway activity increases during oxidative stress? (A) NADPH directly activates ribose‑5‑phosphate synthesis (B) NADP⁺ accumulation activates glucose‑6‑phosphate dehydrogenase (C) ATP depletion stimulates the oxidative phase (D) Glutathione directly activates transketolase