Water splitting, in which water is decomposed into its component protons, electrons, and oxygen, occurs in the light reactions in all photosynthetic organisms. Some such organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast. Efforts have been undertaken to genetically modify cyanobacterial hydrogenases to efficiently synthesize H2 gas even in the presence of oxygen. Efforts have also been undertaken with genetically modified alga in a bioreactor. COUNT 4
QSN1 What is the decomposition of water into its components called? ANS1 Water splitting QSN2 Where does water splitting occur? ANS2 in the light reactions in all photosynthetic organisms QSN3 What organisms can form H2 gas? ANS3 alga Chlamydomonas reinhardtii and cyanobacteria QSN4 How are these gases formed? ANS4 by specialized hydrogenases in the chloroplast