ExamPrepWay
Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Learn + solve
Solve this faster with the right shortcut first
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 6
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 6: What band pattern is expected on reducing SDS-PAGE for the purified enzyme?
Explanation
Correct Answer: B
ANSWER
Correct Answer: B
Method / Topic: Biochemistry
The correct answer is B: One band at 40 kDa. The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is B: One band at 40 kDa. The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band.
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 6: What band pattern is expected on reducing SDS-PAGE for the purified enzyme?
ANSWER
Correct Answer: B
Method / Topic: Biochemistry
The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band. To solve this kind of MCAT biochemistry
Need the full method?
See full explanation + shortcut trick
Compare the quick idea with the premium step-by-step explanation and faster solving trick for this pattern.
Question 6
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 6: What band pattern is expected on reducing SDS-PAGE for the purified enzyme?
Explanation
Correct Answer: B
ANSWER
Correct Answer: B
Method / Topic: Biochemistry
The correct answer is B: One band at 40 kDa. The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is B: One band at 40 kDa. The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band.
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 6: What band pattern is expected on reducing SDS-PAGE for the purified enzyme?
ANSWER
Correct Answer: B
Method / Topic: Biochemistry
The reducing agent breaks the intersubunit disulfide bond, and SDS disrupts noncovalent interactions. Because the 80-kDa dimer contains two equal subunits, each polypeptide is 40 kDa and both migrate to the same position, producing one band. To solve this kind of MCAT biochemistry
Locked premium value
See full explanation + shortcut trick
Use the free answer check first, then unlock the complete breakdown, shortcut path, and richer explanations for similar questions.
Keep Practicing This Pattern
Topic Recommendations
Practice Similar Questions
Recommended Next Practice
Use these suggestions after solving the practice questions above.
PYQ-style pattern
Concept tagged
Identify the tested biochemical principle
use the passage data
Biochemistry · Easy
Q11629: PASSAGE 1 — ENZYME KINETICS
Researchers study an enzyme that converts substrate S to prod…
Biochemistry · Easy
Q11633: PASSAGE 2 — PROTEIN PURIFICATION
A soluble cytosolic enzyme has an isoelectric point (pI)…
Biochemistry · Easy
Q11637: PASSAGE 3 — MITOCHONDRIAL RESPIRATION
Isolated mitochondria receive succinate as the only…
Biochemistry · Easy
Q11641: QUESTION 13: Which amino-acid side chain is most likely to carry a positive charge at phy…