β Scribed by SILKE THOMS; MARKUS PAHLOW; DIETER A. WOLF-GLADROW
No coin nor oath required. For personal study only.
A generic chloroplast-based model for the carbon concentrating mechanism (CCM) in eukaryotic algae is presented. The "ne structure of chloroplasts is represented by separate compartments: marginal and bulk stroma, pyrenoid, girdle lamella, bulk thylakoids, and central lamella traversing the pyrenoid. The roles of the individual structural elements of the chloroplast with respect to the CCM and the e!ect of carbonic anhydrase activity in various compartments are analysed. Hypothetical HCO\ transport into the acidic thylakoid lumen is adjusted by imposing an optimization principle: a given [CO ] at the site of RuBisCO is achieved with minimum energy costs for the CCM. Our model is highly e$cient in terms of saturation of RuBisCO carboxylase activity and the a$nity of the chloroplast for CO , if either a girdle lamella or a pyrenoid is present. The highest e$ciency is achieved with a pyrenoid. A eukaryotic CCM is not necessarily associated with accumulation of dissolved inorganic carbon (DIC) as in cyanobacteria. Chloroplasts are categorized into four types corresponding to morphological characteristics of all major algal classes with regard to the presence of pyrenoids, girdle lamellae, and the distribution of CA activity.
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## I k p a i t m e n t of Physiology, S e w P o r k University CoEZege of Medicine, New Y o l k aiid the &It.