What happens to the egg in lemon juice?

When an egg is placed in lemon juice, the acidic nature of the lemon juice causes a chemical reaction to take place. The acid in the lemon juice denatures the proteins in the egg white, causing them to coagulate and form a solid structure. This process is known as coagulation. The egg yolk, which is mainly composed of fats, is not affected by the lemon juice and remains liquid.

The overall effect is the transformation of the egg from a liquid state into a solid state. This process is commonly used in cooking to make dishes such as poached eggs, pickled eggs, and lemon curd.