A student determines the isoelectric point (the pH corresponding to zero net
charge) of a protein in an aqueous solution by lowering the pH until
precipitation of the protein is observed. During this process, the student
records an initial pH of 6.25 (protein is in solution), then upon addition of
acid, the pH decreases to 5.75 and the protein is found to have precipitated
from solution. The student should record the isoelectric point of the protein
as:

a. 6.00 ± 0.50
b. 6.00 ± 0.25
c. 5.75 ± 0.50
d. 6.25 ± 0.25
e. 5.75 ± 0.25

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