Question

Avidin present in raw egg white will reduce the availability of which of the following?

• A. Biotin
• B. Ascorbic acid
• C. Folic acid
• D. Carotene

Hint:

Antinutritional Factors:
AVIDIN (Raw Egg White) $\rightarrow$ Binds BIOTIN (Vitamin $\text{B}_7$).
Phytate (Cereals) $\rightarrow$ Binds Zinc/Iron/Calcium.
Thiaminase (Raw Fish) $\rightarrow$ Destroys Thiamine ($\text{B}_1$).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Nutritional antinutritional factors: the tetrameric glycoprotein avidin in raw egg white binds water-soluble Vitamin B7 (biotin) with extreme affinity ($K_d pprox 10^{-15} ext{ M}$), creating an unabsorbable complex.
Key Formula or Approach:
\[ \text{Avidin (Raw Egg White)} + \text{D-Biotin (Vitamin } \text{B}_7) \xrightarrow{K_d \approx 10^{-15}\text{ M}} \mathbf{Avidin-Biotin \text{ } Complex (Indigestible / Excreted)} \]

Step 2: Detailed Explanation:
In nutritional biochemistry and antinutritional factors:
- Avidin is a basic tetrameric glycoprotein present in the albumen (raw egg white) of poultry eggs:
- Each avidin molecule possesses four independent binding sites that bind the B-complex vitamin Biotin (Vitamin B7 Vitamin H) with one of the tightest non-covalent affinities known in biology ($K_d \approx 10^{-15}\text{ mol/L}$).
- The resulting Avidin-Biotin complex is completely resistant to gastrointestinal proteolytic digestion, preventing intestinal absorption of biotin and precipitating 'egg white injury' (severe biotin deficiency dermatitis alopecia). (Cooking denatures avidin, eliminating this antinutritional effect).

Step 3: Final Answer:
Thus, Avidin reduces the availability of Biotin, corresponding to option (A).