||John A. Raven Functional evolution of photochemical energy transformations in oxygen-producing organisms, Functional Plant Biology, 2009, 36, 505–515 p.512 left column top paragraph
||1) Raven JA (1984) A cost-benefit analysis of photon absorption by photosynthetic unicells. New Phytologist 98, 593–625. (2) Raven JA (1984) ‘Energetics and transport in aquatic plants.’ (A. R. Liss: New York) (3) Alberte RS (1989) Physiological and cellular features of Prochloron. In ‘Prochloron: a microbial enigma’. (Eds RA Lewin, L Chang) pp. 31–52. (Chapman and Hall: New York) (4) Ting CS, Rocap G, King J, Chisholm SW. Cyanobacterial photosynthesis in the oceans: the origins and significance of divergent light-harvesting strategies. Trends Microbiol. 2002 Mar10(3):134-42.PubMed ID11864823
||The higher capacity to harvest photons at incipient light saturation (Ek) in oxygenic organisms is paralleled by a higher chromophore density per unit area of membrane. Thus, the kDa protein corresponding to 1 mol of chlorophyll and (lightharvesting) carotenoid in light-harvesting and reaction centre pigment–protein complexes in oxygenic organisms lacking phycobilin antennae is 2.0–6.3, whereas the value for phycobilin antennae is 5.8–15.7 (Raven 1984a, 1984b Alberte 1989 Ting et al. 2002) BNID 105058. For rhodopsin ion pumps the corresponding value is 26 (Raven 1984b), BNID 105059. This makes rhodopsins much more costly in terms of energy and nitrogen to synthesise than the light-harvesting and photochemical machinery of oxygenic organisms (Raven 1984a, 1984b Alberte 1989 Ting et al. 2002). Even when the other electron transfer and proton pump components in oxygenic organisms (e.g. cytochrome b6–f complex, cytochrome c6 or plastocyanin, ferredoxin or flavodoxin) are considered (see Raven et al. 1999), the nitrogen and energy costs of rhodopsins are still significantly higher per unit chromophore than the oxygenic organism’s machinery.