50. ATPase
A.synthesizes ATP, coupled to transfer of extracellular protons into the cell
B.extrudes protons from the cell coupled to the hydrolysis of ATP to ADP
C.is the enzyme that incorporates ATP into messenger RNA
D.carries out each of the reactions indicated in (a) and (b)

---

51. Which of the following is responsible for phosphate solubilization?
A.Streptococcus
B.Streptomyces
C.Bacillus
D.Clostridium

---

52. Phosphate deregulated mutants are
A.less sensitive to phosphate regulation
B.moderately sensitive to phosphate regulation
C.highly sensitive to phosphate regulation
D.none of these

---

53. The mechanism of passive or facilitated diffusion require
A.metabolic energy
B.concentration of solute against an electrochemical gradient
C.accumulation of solute against an electrochemical gradient
D.accumulation or concentration of solute against an electrochemical gradient

---

54.  Nitrogen fixation is a process that requires
A.energy
B.an anaerobic environment
C.both (a) and (b)
D.an aerobic environment

---

55. Bacteriochlorophyll differs from chlorophyll in what way?
A.The chelated metal in bacteriochlorophyll is not Mg
B.There are chemical differences between the two chlorophyll in their side (R) groups
C.They have different absorption spectra
D.Both (b) and (c)

---

56. Radioisotopes are frequently used in the study of cells. Assume a culture of E. coli is grown in a culture medium containing radioactive sulphur. At the end of 48 hours, it is expected to find the radioactive label located in
A.DNA
B.enzymes
C.RNA
D.all of these

---