thylakoidcontaining

Thylakoid-containing describes cells or organelles that possess thylakoid membranes, the membrane-bound sacs where the light-dependent reactions of photosynthesis take place. Thylakoids are found inside chloroplasts of green plants, algae, and some protists, as well as in cyanobacteria and some other photosynthetic bacteria. In plants and algae, thylakoids are typically arranged into stacked grana connected by stroma lamellae; in cyanobacteria, thylakoid membranes are often distributed more diffusely within the cytoplasm and are not organized into grana.

Structurally, a thylakoid membrane encloses a thylakoid lumen and contains the protein complexes required for photosynthesis, including photosystem II and photosystem I, the cytochrome b6f complex, ATP synthase, and various electron carriers such as plastoquinone and plastocyanin. Pigments such as chlorophylls and carotenoids are embedded in the membrane, capturing light energy and driving the transfer of electrons to generate a proton motive force across the membrane. This proton gradient powers ATP synthesis, while electrons are ultimately transferred to ferredoxin and NADP+, forming NADPH.

Functionally, thylakoids conduct the light reactions of photosynthesis, converting light energy into chemical energy stored as ATP and NADPH. The organization of thylakoid membranes can vary among lineages, with higher plants showing distinct grana and stroma lamellae, while cyanobacteria typically display a different arrangement. The presence of thylakoid membranes is a defining feature of oxygenic photosynthesis and is central to primary production in many ecosystems.