Q.8 Biological value of proteins can be defined as –
- BV = (Nitrogen retained / Nitrogen absorbed) × 100
- BV = (Nitrogen retained / Nitrogen ingested) × 100
- BV = Nitrogen retained / (Nitrogen absorbed − Nitrogen retained) × 100
- BV = (Nitrogen absorbed / Nitrogen ingested) × 100
Biological value of proteins measures how efficiently the body utilizes absorbed protein nitrogen, calculated as BV = (Nitrogen retained / Nitrogen absorbed) × 100, making option 1 correct for assessing protein quality in nutrition and biochemistry.
Option Analysis
1. BV = (Nitrogen retained / Nitrogen absorbed) × 100
This standard formula reflects the proportion of absorbed nitrogen incorporated into body tissues, excluding fecal losses but accounting for urinary/endogenous excretion; egg protein scores ~100%.
2. BV = (Nitrogen retained / Nitrogen ingested) × 100
This describes Net Protein Utilization (NPU), not BV, as it includes all ingested nitrogen before absorption, underestimating true utilization.
3. BV = Nitrogen retained / (Nitrogen absorbed − Nitrogen retained) × 100
Incorrect; this inverts the efficiency metric and lacks biological basis, as it would yield nonsensical values unrelated to retention efficiency.
4. BV = (Nitrogen absorbed / Nitrogen ingested) × 100
This is the digestibility coefficient, measuring absorption fraction, not retention after absorption.
Protein Quality Metrics Compared
Metric Formula Measures Example (Egg) Biological Value (BV) Retained / Absorbed × 100 Utilization efficiency 100% Net Protein Utilization (NPU) Retained / Ingested × 100 Overall retention 94% Digestibility Absorbed / Ingested × 100 Absorption fraction 97% Key for plant sciences (e.g., legume proteins ~70% BV) and molecular biology exam prep on nutrient metabolism.
