AP BIOLOGY

Detailed explanation-1: -Physically, photosystems are found in the thylakoid membranes. There are two kinds of photosystems: photosystem I (PSI) and photosystem II (PSII) (Fig. 3.3). PSII acts first during the light transformation process in photosynthesis, but it was named PSII because it was discovered second.

Detailed explanation-2: -Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.

Detailed explanation-3: -The thylakoid membrane is characterized by a unique composition of proteins, lipids, pigments and multiple cofactors. As MGDG, one of the two major lipids, is a non-bilayer forming lipid, the interplay of lipids and proteins seems to be important for thylakoid formation.

Detailed explanation-4: -Photosystem II (PSII) is a multi-subunit pigment-protein complex found in thylakoid membranes of oxygenic photosynthetic organisms, including cyanobacteria, algae, and plants (Nickelsen and Rengstl, 2013; Järvi et al., 2015). Driven by light, PSII catalyzes electron transfer from water to plastoquinone.

Detailed explanation-5: -Two types of photosystems, photosystem I (PSI) and photosystem II (PSII), are found in the thylakoid membrane inside the chloroplast. Each photosystem consists of multiple antenna proteins that contain a mixture of 300–400 chlorophyll a and b molecules, as well as other pigments like carotenoids.