| Value |
8
%
Range: Table - link %
|
| Organism |
prokaryote |
| Reference |
John A. Raven Functional evolution of photochemical energy transformations in oxygen-producing organisms, Functional Plant Biology, 2009, 36, 505–515 p.511 table 1 |
| Primary Source |
Falkowski PG, Raven JA (2007) ‘Aquatic photosynthesis, 2nd edn’. (Princeton University Press: Princeton) |
| Method |
Comparing the operating costs of oxygenic photosynthesis, moving one electron from water to NADP+ with the coupled pumping of three protons across the photosynthetic membrane takes at least two absorbed photons given the relatively low photon yield of PSII. The energy stored in the products listed in the last sentence is 110 kJ + (3×18 kJ) or 164 kJ per mol electron moved (Raven 1984b), BNID 105060. One mol 680 nm photon (PSII) contributes 176 kJ and one mol 700 nm photon (PS1) contributes 171 kJ, a total of 347 kJ. Even with 100% photochemical efficiency of both photosystems the overall efficiency of energy capture is 164/347 (i.e. 47%) (Table link, BNID 105061). For the mean wavelength of photosynthetically active radiation (i.e. 550 nm), the efficiency is 163/(2×218) or 37%. For an ion-pumping rhodopsin with an absorption maximum at 550 nm, the energy input is 218 kJ per mL photon. As the energy stored in the movement of a single mol of protons is only 18 kJ, BNID 105062, the efficiency is only 8% |
| Comments |
8% efficiency in transmembrane H+ electrochemical potential difference. Efficiency of photon energy use
percentage of absorbed excitation
energy stored in the specified end products. Bacteriorhodopsin is an integral membrane protein usually found in two-dimensional crystalline patches known as "purple membrane", which can occupy up to nearly 50% of the surface area of the archaeal cell. Data in table for purple membrane with half the area occupied by ion-pumping rhodopsin. |
| Entered by |
Uri M |
| ID |
105056 |