Q.29 The degree of reduction of lactic acid (C3H6O3) is ________________.
Degree of Reduction of Lactic Acid (C3H6O3)
The degree of reduction for lactic acid, with formula C3H6O3, equals 4 per carbon atom. This value arises from the standard biochemistry formula applied to its atomic composition.
Calculation Method
Degree of reduction (γ), also called the reduction level or available electrons per carbon, uses the formula γ = [4c + h – 2o]/c. Here, c=3 (carbons), h=6 (hydrogens), o=3 (oxygens). Substituting gives γ = [4(3) + 6 – 2(3)] / 3 = (12 + 6 – 6)/3 = 12/3 = 4.
Step-by-Step Breakdown
- Multiply carbons by 4 (valence electrons available): 4 × 3 = 12
- Add hydrogens (oxidation state +1): +6
- Subtract twice oxygens (oxidation state -2): -2 × 3 = -6
- Total electrons = 12; divide by carbons = 4 per C
Why It Matters in Biochemistry
This metric quantifies oxidation state relative to CO2 (γ=0) or CH4 (γ=8), aiding yield predictions in fermentation or respiration. Lactic acid’s γ=4 matches pyruvate’s, reflecting no net redox change in glycolysis-to-lactate conversion.
Common Exam Options Explained
| Option | Value | Explanation |
|---|---|---|
| 2 | Too low | Fits more oxidized compounds like glyoxylate (higher O:C ratio). |
| 4 | Correct | Matches C3H6O3 calculation; standard for lactate in biotech GATE questions. |
| 6 | Too high | Seen in less oxidized organics like alcohols (e.g., ethanol γ=6). |
| 8 | Maximum | Pure hydrocarbons like methane; irrelevant here. |
