Thylakoidrelated

Thylakoid-related is a term used to describe concepts, structures, and processes associated with thylakoids, the membrane-bound sacs inside chloroplasts of plants and algae and in cyanobacteria. Thylakoids are the site of the light-dependent reactions of photosynthesis and host most of the pigment–protein complexes that capture light energy and drive electron transport. The term can refer to thylakoid membranes themselves, the thylakoid lumen, or proteins and pathways that operate within or across these compartments.

Thylakoid membranes form a layered network in chloroplasts, with stacks of flat disks called grana interconnected by stroma lamellae. The internal space between the membranes is the thylakoid lumen, while the surrounding liquid is the stroma. These membranes contain the photosystems II and I, cytochrome b6f, ATP synthase, light-harvesting complexes, and various electron carriers such as plastoquinone and plastocyanin. The lipid composition and protein organization support efficient light harvesting and proton gradient generation.

During photosynthesis, light energy is used to drive electron transport through the thylakoid membrane, pumping protons into the lumen and creating a proton motive force. This power drives ATP synthase to produce ATP and, in concert with ferredoxin-NADP+ reductase, generates NADPH. Water-splitting at photosystem II releases oxygen. Thylakoid membranes also participate in photoprotection and the assembly of photosynthetic complexes.

Thylakoid-related topics include the targeting and insertion of proteins into thylakoids via Sec, Tat, or SRP pathways, thylakoid biogenesis, and the evolution of thylakoid membranes in cyanobacteria and plants. The term is commonly used in research labeling, protein localization annotations, and functional descriptions of chloroplast light reactions.

See also: thylakoid, chloroplast, photosystem II, photosystem I, photophosphorylation, thylakoid lumen, grana.