Q115 · Practice questionComplex familiar1 mark
QUESTION 115
Amino acid X migrates towards the negative electrode at pH 4.0 and towards the positive electrode at pH 8.0. Which isoelectric point is consistent with both observations?
(A)
6.0
(B)
4.0
(C)
2.0
(D)
10.0
WORKED SOLUTION
1 markAnswer A
Answer
A
Working
At pH 4.0 it is net positive, so pH < pI. At pH 8.0 it is net negative, so pH > pI. Only pI = 6.0 lies strictly between the two values.
Marking criteria
- Select A. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
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