Question

What will happen to a crude extract of urease when it is purified by gel filtration?

• A. Amount of total protein increases \
• B. Its specific activity decreases \
• C. Its specific activity increases \
• D. Amount of total protein remain same

Hint:

Purification rule of thumb: Every step should lower total protein weight but increase the target enzyme's specific activity ($\text{Units/mg}$).

Answer 1

The Correct Option is C

Step 1: Concept Protein purification techniques use variations in physical characteristics (like size, charge, or solubility) to isolate a specific target enzyme from a complex mixture of non-target cellular proteins.

Step 2: Meaning * Total activity: Cumulative catalytic output of the target enzyme in the sample. * Specific activity: Enzymatic units per milligram of total protein present ($\text{Units/mg}$). It serves as the standard biochemical metric for sample purity.

Step 3: Analysis * Gel filtration chromatography separates components by molecular size, filtering away smaller or larger contaminating non-target proteins. * As these contaminant proteins are removed, the total amount of protein in the sample drops while the targeted urease activity is preserved. * According to the formula: $$\text{Specific Activity} = \frac{\text{Total Activity Units}}{\text{Total Protein Weight (mg)}}$$ * As the denominator (total protein) decreases, the specific activity calculation climbs.

Step 4: Conclusion Successful purification steps always lead to an increase in the specific activity of the target enzyme, matching option C. Final Answer: (C)