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Shortcut used: Identify the tested biochemical principle, track charge/carbon/electrons or pathway direction, use the passage data, and reject choices that contradict cellular location or chemical behavior.
Solve in 3 steps:
- Mark the given values and the exact target.
- Apply the relevant formula, rule, or concept.
- Check the final value against the options.
Common mistake: Do not choose an option before confirming the exact demand of the question.
Question 5
Multiple Choice Question
Question
PASSAGE 2 — PROTEIN PURIFICATION
A soluble cytosolic enzyme has an isoelectric point (pI) of 5.2 and forms a disulfide-linked dimer. Scientists purify it at pH 7.5 using anion-exchange chromatography, then size-exclusion chromatography. They analyze samples by SDS-PAGE with and without a reducing agent. The native dimer has a molecular mass of 80 kDa, and its two subunits have equal mass.
QUESTION 5: In size-exclusion chromatography, which species generally exits the column first?
Explanation
Correct Answer: A
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
The correct answer is A: The largest protein species. Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is A: The largest protein species. Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI.
Detailed Explanation
Question
PASSAGE 2 — PROTEIN PURIFICATION
A soluble cytosolic enzyme has an isoelectric point (pI) of 5.2 and forms a disulfide-linked dimer. Scientists purify it at pH 7.5 using anion-exchange chromatography, then size-exclusion chromatography. They analyze samples by SDS-PAGE with and without a reducing agent. The native dimer has a molecular mass of 80 kDa, and its two subunits have equal mass.
QUESTION 5: In size-exclusion chromatography, which species generally exits the column first?
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI. To solve this kind of MCAT biochemistry
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Question 5
Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Learn + solve
Shortcut used, common trap, and the fastest solving route
Shortcut used: Identify the tested biochemical principle, track charge/carbon/electrons or pathway direction, use the passage data, and reject choices that contradict cellular location or chemical behavior.
Solve in 3 steps:
- Mark the given values and the exact target.
- Apply the relevant formula, rule, or concept.
- Check the final value against the options.
Common mistake: Do not choose an option before confirming the exact demand of the question.
Question
PASSAGE 2 — PROTEIN PURIFICATION A soluble cytosolic enzyme has an isoelectric point (pI) of 5.2 and forms a disulfide-linked dimer. Scientists purify it at pH 7.5 using anion-exchange chromatography, then size-exclusion chromatography. They analyze samples by SDS-PAGE with and without a reducing agent. The native dimer has a molecular mass of 80 kDa, and its two subunits have equal mass. QUESTION 5: In size-exclusion chromatography, which species generally exits the column first?
Explanation
Correct Answer: A
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
The correct answer is A: The largest protein species. Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is A: The largest protein species. Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI.
Detailed Explanation
Question
PASSAGE 2 — PROTEIN PURIFICATION
A soluble cytosolic enzyme has an isoelectric point (pI) of 5.2 and forms a disulfide-linked dimer. Scientists purify it at pH 7.5 using anion-exchange chromatography, then size-exclusion chromatography. They analyze samples by SDS-PAGE with and without a reducing agent. The native dimer has a molecular mass of 80 kDa, and its two subunits have equal mass.
QUESTION 5: In size-exclusion chromatography, which species generally exits the column first?
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
Large molecules enter fewer pores in the beads and therefore take a shorter path through a size-exclusion column. Small molecules enter more pores and are delayed. Elution here depends mainly on hydrodynamic size, not charge or pI. To solve this kind of MCAT biochemistry
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