Granas (Lat. Granum - Grain)

Small bodies in chloroplasts; consist of alternating layers of chlorophyll, protein and lipid and are the functional units in the process of photosynthesis.

Granas are disk-shaped structures with a diameter of 0.2-0.8 microns. They are located in the stroma of chloroplasts and consist of thylakoid membranes that contain chlorophyll molecules. Thylakoid membranes alternate with layers of proteins and lipids. This ordered structure makes it possible to capture light energy as efficiently as possible and carry out photosynthetic reactions.

Granas play a key role in the light phase of photosynthesis. It is in them that light quanta are absorbed and electrons are transferred, triggering the formation of ATP and NADP H+. Thus, grana act as functional units that ensure the conversion of light energy into the energy of chemical bonds in the process of photosynthesis. Their unique structure allows them to effectively collect light energy and direct it to the synthesis of organic substances from carbon dioxide and water.