49. Nitrogen fixation is observed in some plant species. Which one of the following statement is correct about nitrogen fixation?
(A) N₂ will be converted to NO₃^- .
(B) Nitrifying bacteria are able to fix nitrogen gas.
(C) This occurs in aerobic environment.
(D) This may produce hydrogen gas.
(E) This is catalyzed by nitrate reductase.

45. In temperate regions, which pigment is responsible for the red-yellow coloration seen in leaves during the color change in autumn? (A) Chlorophyll a (B) Chlorophyll b (C) Carotenoids (D) Porphyrin (E) Anthocyanin

46. If we use 14CO2 as a radioactive tracer to track the carbon transition, which one of the following molecule could be incorporated in the last reaction of Calvin cycle? (A) Glyceraldehyde-3-phosphate (G3P) (B) Ribulose biphosphate (RuBP) (C) 1,3-biphosphoglycerate (1,3-BPG) (D) 3-phosphoglycerate (3PG) (E) Glucose

47. Compare to the function of plasmodesmata in plant cells, which structure serve the same function in animal cells? (A) Gap junctions (B) Middle lamella (C) Hemidesmosomes (D) Tight junctions (E) Basal lamina

48. If the genus Oryza is monophyletic, which one of the following is correct? (A) Oryza all have nearly identical appearance. (B) Oryza cannot be classified in a single family or order. (C) All species of Oryza are descended from a common ancestor. (D) All species of plant are classified as being in a single order. (E) All species of Oryza grow in similar habitats.

50. A circular 3518 bp plasmid DNA has EcoRI restriction sites at position 86 and 1435; PstI sites at position 1108 and 2950; and a BamHI site at position 2623. Which one of the following choices is not correct? (A) EcoRI digestion yields two bands in agarose gel. (B) When digestion with EcoRI and BamHI, three bands will be observed in agarose gel. (C) After digestion with EcoRI, PstI and and BamHI, five bands will be observed in agarose gel. (D) When digestion with EcoRV and PstI, only two bands will be observed in agarose gel. (E) BamHI digestion yields only one band in agarose gel.

51. Endosymbiotic events had occurred multiple times during evolution. Which one of the following organism contain endosymbiont organelles? 1. Green algae 2. Red algae 3. Chlorarachniophytes 4. Euglenids 5. Arabidopsis 6. Rice 7. Mouse 8. Human (A) 1,2 (B) 3,4 (C) 1,2,3,4 (D) 1,2,3,4,5,6 (E) 1,2,3,4,5,6,7,8

52. Which one of the following statement about the immune system is correct? (A) The innate immunity is found in all animals and plants. (B) The adaptive immune response is activated before the innate response and develops quickly. (C) The helper T cells recognize peptide antigens in major histocompatibility complex MHC class I molecules on dendritic cells. (D) Perforin triggers blood vessels to dilate and become more permeable. (E) The complement system provides innate defense by interfering with viruses and helping activate macrophages.

53. In Australia, marsupials fill the niches that placental mammals fill in other parts of the world because ________. (A) after Pangaea broke up, they diversified in physical isolation from placental mammals (B) they originated in Australia (C) they evolved from monotremes that migrated to Australia about 50 million years ago (D) human-caused environmental changes have favored the success of marsupials (E) they are better adapted and have outcompeted placental mammals (eutherians)

54. What is the function of the cilia in the trachea and bronchi? (A) To sweep mucus with trapped particles up and out of the respiratory tract. (B) To increase the surface area for gas exchange. (C) To vibrate when air is exhaled to produce sounds. (D) To dislodge food that may have slipped past the epiglottis. (E) To sweep air into and out of the lungs.

55. Which one of the following statement is correct description about the COVID-19 virus? (A) During COVID-19 virus reproduction, spike glycoproteins are assembled into the virus along with reverse transcriptase. (B) Successful entry of a virus into a cell depends on the inactivation of envelope glycoproteins by host cell proteases. (C) COVID-19 virus replication entails ribosome frameshifting during genome translation, and the synthesis of both genomic and multiple subgenomic RNA species. (D) COVID-19 virus are enveloped DNA viruses that are spherical in shape and characterized by crown-like spikes on the surface. (E) Persons often die of opportunistic diseases because COVID-19 virus destroys T cells.