What is the phospholipid found in egg yolk and soy?

Lecithin is a type of phospholipid that is abundant in egg yolk and soybeans. It plays a crucial role in cell membrane structure and function due to its unique molecular composition, which allows it to interact with both water and fat. This amphiphilic nature makes lecithin an effective emulsifier, helping to stabilize emulsions like mayonnaise and sauces by keeping oil and water mixed.

In the culinary context, lecithin is often used in various applications, including baking and dressings, to enhance texture and consistency. Its presence in egg yolk makes it a key ingredient in many classic recipes, while soy-based lecithin serves as a popular alternative in vegan cooking. The other substances listed do not share these properties or functions, which is why lecithin is the correct choice here.