20. Which of the following is an example of a secondary messenger in signal transduction pathways?
(A) Epidermal growth factor (EGF)
(B)RNA
(C)CAMP
(D)ATP

16. Which of the following is NOT a characteristic of enzymes? (A) Enzymes are specific to a particular substrate. (B) Enzymes are consumed in the chemical reaction they catalyze. (C) Enzymes lower the activation energy required for a chemical reaction to occur. (D) Enzymes can be regulated by inhibitors and activators

17. Which of the following is NOT a type of cell junction found in animal tissues? (A) Tight junctions (B) Desmosomes (C)Gap junctions (D) Plasmodesmata

18. Which of the following is an example of negative feedback in the human body? (A) The release of insulin in response to high blood glucose levels (B) The release of cortisol in response to stress (C) The contraction of the uterus during childbirth (D) The release of oxytocin during breastfeeding

19. In meiosis, homologous chromosomes pair up during which phase? (A) Prophase l (B)Metaphase I (C) Anaphase | (D) Telophase l

21. What is the role of the Krebs cycle (also known as the citric acid cycle) in cellular respiration? (A) To generate ATP by oxidative phosphorylation (B) To convert glucose into pyruvate (C) To produce NADH and FADH2 for use in the electron transport chain (D) To synthesize glucose from pyruvate

22. Which one of the following statements is NOT true for human immune system? (A) T cells belong to specific immunity. (B) Neutrophils belong to nonspecific immunity. (C) Inactivated antigens are eliminated from the body by nonspecific defenses such as complementation. (D) IgA is the first to be produced during an initial immune response

23. Which one of the following statements is NOT true for the mammalian circulation system? (A) Both arteries and veins have an endothelium, smooth muscle, and connective tissue. (B) Both arteries and veins contain valves to maintain unidirectional blood flow. (C) Blood flow in capillaries is necessarily slow for exchange of materials. (D) The recoil of elastic arterial walls plays a role in maintaining blood pressure.

24. Which one of the following statements is NOT true regarding the human reproductive system? (A) In the human male reproductive system, the function of seminal vesicles is to store sperms. (B) Human ovulation is triggered by surge of luteinizing hormone (LH). (C) Cilia in the oviduct convey the eggs to the uterus. (D) In human, the main sex hormones are steroid hormones.

25. Which one of the following statements is NOT true regarding the respiration system? (A) In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface. (B) Respiratory surfaces are always thin and moist. (C) Fish gills use a countercurrent exchange system to increase blood flow. (D) In human lungs, cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx.

26. Which one of the following statements is NOT true regarding the human endocrine system? (A) The posterior pituitary is an extension of the hypothalamus. (B) The parathyroid glands play a major role in blood Ca2+ regulation. (C) Many neurohormones regulate endocrine signalling. (D) All the hormones secreted from anterior pituitary have effects on other endocrine glands.