Thylakoid membranes are integral components of chloroplasts found in plant cells and some algae. These membranes play a crucial role in the process of photosynthesis by hosting the light-dependent reactions. Structurally, thylakoid membranes are composed of a lipid bilayer that encloses the thylakoid lumen, which is integral for the formation of ATP and NADPH, the energy currencies of the cell.