Question

The fat globule membrane is composed of

• A. Phospholipids and lipoproteins
• B. Alpha-lactalbumin and Beta-lactoglobulin
• C. Casein and lactose
• D. Serum protein and whey proteins

Hint:

Milk Fat Globule Membrane (MFGM): Composed of PHOSPHOLIPIDS AND LIPOPROTEINS Glycoproteins (Sphingomyelin, Phosphatidylcholine, Butyrophilin, Xanthine oxidase).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bovine milk fat globule membrane (MFGM) molecular architecture: the native MFGM is a 10--50 nm trilayer envelope derived from the apical mammary epithelial plasma membrane, composed of polar phospholipids (sphingomyelin, phosphatidylcholine, PE, PI, PS) complexed with specific glycoproteins and lipoproteins.
Key Formula or Approach:
\[ \text{MFGM Composition: } \mathbf{Polar \text{ } Phospholipids (30\%)} + \mathbf{Membrane \text{ } Lipoproteins / Glycoproteins (60\%)} + \text{Enzymes (Xanthine Oxidase, ALP)} \]

Step 2: Detailed Explanation:
In milk fat physical biochemistry and emulsion structure:
- Milk Fat Globule Membrane (MFGM) (A): A complex, amphiphilic biological trilayer membrane ($10 - 50\text{ nm}$ thick) surrounding native milk fat droplets ($0.1 - 15\;\mu\text{m}$) that lowers interfacial tension from $45\text{ mN/m}$ to $1 - 2\text{ mN/m}$, preventing spontaneous coalescence:
1. Lipid Fraction ($\approx 30\% - 40\%$): Rich in Polar Phospholipids (Sphingomyelin, Phosphatidylcholine, Phosphatidylethanolamine, Phosphatidylserine, Phosphatidylinositol) and free cholesterol.
2. Protein Fraction ($\approx 60\% - 70\%$): Specific Lipoproteins and Glycoproteins (Mucin-1, PAS 6/7, Butyrophilin, Xanthine Dehydrogenase/Oxidase, CD36, and membrane-associated Lipoprotein Lipase).
- Therefore, the native fat globule membrane is composed of Phospholipids and lipoproteins.

Step 3: Final Answer:
Thus, the fat globule membrane is composed of Phospholipids and lipoproteins, matching option (A).