This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following is the main component of plasma membrane? 
Select and explain. 
A. Proteins, B. Lipids, C. Carbohydrates, D. Phospholipids
A: Proteins
Answer: A: Proteins 
Explanation: Proteins - 55% Cholestrol - 13% Phospholipids - 25% Carbohydrates - 3% Phospholipids are a major component of cell membranes. They form a lipid bilayer in which their hydrophillic (attracted to water) head areas spontaneously arrange to face the aqueous cytosol and the extracellular fluid, while their hydrophobic (repelled by water) tail areas face away from the cytosol and extracellular fluid. The lipid bilayer is semi-permeable.