Question

Protein Efficiency Ratio (PER) is_________

• A. Gain in the body weight per unit of protein intake
• B. Percentage of protein absorbed after digestion
• C. Product of digestibility coefficient and biological value
• D. Percentage of nitrogen retained out of nitrogen absorbed

Hint:

Mnemonic: PER = Protein Evaluation by Rats. Since it depends on weight gain (growth), it's most relevant for growing organisms.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the definition of the Protein Efficiency Ratio (PER), which is a physiological method for evaluating the nutritional quality of a protein source.
Key Formula or Approach:
The Protein Efficiency Ratio is calculated as:
\[ PER = \frac{\text{Gain in body mass (grams)}}{\text{Protein intake (grams)}} \] This test is typically performed using young rats over a standardized period (e.g., 28 days).

Step 2: Detailed Explanation:

• Concept: PER measures how effectively an animal can utilize a specific dietary protein for growth. It is an "in-vivo" assay. Casein is often used as a reference protein with a standardized PER value.

• Significance: A high PER indicates that the protein contains a well-balanced profile of essential amino acids required for tissue synthesis. Low values suggest a deficiency in one or more essential amino acids.

• Distinction from other terms:
• Biological Value (BV): Defined by option (D) - the percentage of absorbed nitrogen that is retained by the body.

• Net Protein Utilization (NPU): Defined by option (C) - the product of digestibility and biological value ($NPU = Digestibility \times BV$).

• Digestibility: Related to option (B) - how much of the ingested protein is actually absorbed.

Step 3: Final Answer:
PER specifically refers to the ratio of weight gain to the amount of protein consumed. Thus, option (A) is the correct definition.