When there is a lack of magnesium in the plant, yellowing of the leaves is observed. Why does this happen?

The process of photosynthesis takes place in the leaves, one of the conditions of which is the presence of chlorophyll.
Chlorophyll is the green pigment in chloroplasts. By its chemical nature, chlorophyll is a protein of a quaternary structure, where individual protein globules are connected by magnesium atoms. It is magnesium that gives the pigment its green color. Therefore, with a lack of magnesium in the plant, yellowing of the leaves is observed, since chlorophyll is destroyed.