Final answer:
The thylakoid membrane in cyanobacteria is an infolded plasma membrane that contains photosynthetic pigments crucial for converting light energy into chemical energy.
Step-by-step explanation:
The thylakoid membrane of the cyanobacterium is an infolded region of the plasma membrane. Photosynthetic pigments, such as chlorophyll, are located within these membranes and are crucial in the process of photosynthesis, where light energy is converted into chemical energy. Contrasting with the eukaryotic chloroplasts, which have their own double membrane, the cyanobacterial thylakoid membrane is not separated by an additional membrane envelope but is rather an extension of the cell's plasma membrane.