Hill reaction

Chloroplasts have the ability to photosynthesize when exposed to light and thereby generate oxygen. In-vitro , chloroplasts need an artificial, non-biological electron acceptor to split water into hydrogen and oxygen . This is known as the Hill reaction , after the discoverer Robert Hill . The electron acceptor is also known as Hill's reagent . 2,6-Dichlorophenolindophenol (DCPIP) is often used to demonstrate the Hill reaction . It is blue in the oxidized form and colorless in the reduced form. DCPIP is added to a leaf extract in experiments and it becomes colorless when illuminated. If there is no lighting, DCPIP retains its blue color. The discoloration comes from the transfer of electrons to the electron acceptor. In chloroplasts, NADP ^{+ is} the biological electron acceptor, as demonstrated by Severo Ochoa . So the Hill equation is:

${\displaystyle \mathrm {2\ H_{2}O+2\ NADP^{+}+Licht\longrightarrow 2\ NADPH+2\ H^{+}+O_{2}} }$

No CO ₂ is directly required for the production of oxygen during photosynthesis . This is also an indication of the origin of the photosynthetic oxygen in the water.

Other electron acceptors such as potassium hexacyanoferrate (III) or artificially added NADP ^{+ also} serve as Hill's reagent .

Individual evidence

1. ↑ Strasburger, Textbook of Botany, Gustav Fischer, 1997.
2. ↑ Entry on Hill reaction. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2014.