Question

What structural feature of lecithin allows it to behave like an emulsifying agent?

Answer 1

Lecithin is an emulsifier agent that's composed of 5 smaller molecules: phosphoric acid, choline, glycerol( is the backbone), and two fatty acids. 

The fatty acids, which are hydrophobic (afraid of water), makes this substance more similiar to fats and represent the non-polar part of the lecithin.
The phosphate group is the polar portion of the molecule and it's the negatively charged. The choline is positively charged, which readily dissolve in water.

Lecithin is a good emulsifier because of these structural features. the hydrophobic contacts with the oil, while the hydrophilic end contacts with the water.