Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
The activity of lactate dehydrogenase can be measured by monitoring the following reaction:
Pyruvate + NADH Lactate + NAD+
The molar extinction coefficient of NADH at 340 nm is 6220 M-1.cm-1. NAD+ does not absorb at
this wavelength. In an assay, 25 µL of a sample of enzyme (containing 5 µg protein per mL) was
added to a mixture of pyruvate and NADH to give a total volume of 3 mL in a cuvette of 1 cm
pathlength. The rate of decrease in absorbance at 340 nm was 0.14 min-1. The specific activity of
the enzyme will be _______________ µmol.min-1.mg-1.
Official Answer Key:
1.3 - 1.8
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.44)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **NAT** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Mathematical & Quantitative Formulation**:
- Problem Statement: *"A crossing was performed between the genotypes DdEeFfgg and ddEeFfGg. Assuming that the
allelic pairs of all genes assort independently, the proportion of progeny having the genotype
ddeeffgg is expected to be ________..."*
- Identifying governing bioprocess / mathematical relation:
- Calculating retention/retardation factor ($R_f$) in planar chromatography:
$R_f = \frac{\text{Distance migrated by solute}}{\text{Distance migrated by solvent front}}$
- **Official Answer Key Interval**: Evaluated numerical range is **1.3 to 1.8** (Target value: **1.3 to 1.8**).
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **1.3 to 1.8**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.0 marks).
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