plastoquinoniin

Plastoquinone is a group of lipophilic molecules found in the thylakoid membranes of chloroplasts in higher plants and cyanobacteria. These molecules are components of the electron transport chain, playing a crucial role in the process of photosynthesis.

Plastoquinones are typically composed of a polyprenyl side chain and a quinone head group. The most common plastoquinone is plastoquinol, which occurs in its reduced form. In contrast, the oxidized form is referred to as plastoquinone.

During photosynthesis, plastoquinone acts as a mobile electron carrier in the electron transport chain of photosystem II. The reduced form of plastoquinone, specifically plastoquinol, is oxidized to plastoquinone upon the transfer of electrons to the electron acceptor pheophytin. This electron transfer enables the subsequent generation of a proton gradient across the thylakoid membrane, driving the synthesis of ATP.

In addition to their role in photosynthesis, plastoquinones are essential for maintaining the integrity and fluidity of the thylakoid membrane. Their lipophilic nature allows them to modulate the membrane's electrical properties, thus affecting the flow of electrons through the electron transport chain. Mutations in the genes encoding plastoquinones can lead to photosynthetic deficiencies and are often associated with reduced growth rates and pigment deficiencies in photosynthetic organisms.

Plastoquinones have also been used as a basis for various pharmaceutical applications. For instance, ubiquinone, a similar lipophilic molecule, is used as a component of certain medications aimed at treating coenzyme Q10 deficiency. The functional similarity between plastoquinones and ubiquinones underlines the relevance of these molecules to human biochemistry.