Membrane permeabilities to CO₂ and HCO₃⁻ constrain the function of CO₂ concentrating mechanisms that algae use to supply inorganic carbon for photosynthesis. In diatoms and green algae, plasma membranes are moderately to highly permeable to CO₂ but effectively impermeable to HCO₃⁻. Here, CO₂ and HCO₃⁻ membrane permeabilities were measured using an ¹⁸O‐exchange technique on two species of haptophyte algae, Emiliania huxleyi and Calcidiscus leptoporus, which showed that the plasma membranes of these species are also highly permeable to CO₂ (0.006–0.02 cm · s⁻¹) but minimally permeable to HCO₃⁻. Increased temperature and CO₂ generally increased CO₂ membrane permeabilities in both species, possibly due to changes in lipid composition or CO₂ channel proteins. Changes in CO₂ membrane permeabilities showed no association with the density of calcium carbonate coccoliths surrounding the cell, which could potentially impede passage of compounds. Haptophyte plasma‐membrane permeabilities to CO₂ were somewhat lower than those of diatoms but generally higher than membrane permeabilities of green algae. One caveat of these measurements is that the model used to interpret ¹⁸O‐exchange data assumes that carbonic anhydrase, which catalyzes ¹⁸O‐exchange, is homogeneously distributed in the cell. The implications of this assumption were tested using a two‐compartment model with an inhomogeneous distribution of carbonic anhydrase to simulate ¹⁸O‐exchange data and then inferring plasma‐membrane CO₂ permeabilities from the simulated data. This analysis showed that the inferred plasma‐membrane CO₂ permeabilities are minimal estimates but should be quite accurate under most conditions.

中文翻译：

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温度和CO2对海洋七足纲植物Emiliaania huxleyi和Calcidiscus leptoporus（Prymnesiophyceae）的质膜透透性对CO2和HCO3的影响。

膜渗透性至CO ₂和HCO ₃ ^-限制CO的功能₂浓缩机制藻类使用用于光合作用提供无机碳。在硅藻和绿藻，质膜是中度至高度可渗透的CO ₂可有效不可渗透HCO ₃ ^- 。在此，CO ₂和HCO ₃ ^-使用测量膜渗透率¹⁸上的两个物种定鞭藻门的藻类，O型交换技术-贺和Calcidiscus leptoporus，这表明，这些物质的等离子体膜也高渗透性至CO₂（0.006-0.02厘米·秒^-1），但最低限度地可渗透HCO ₃ ^- 。升高的温度和CO ₂通常会增加两个物种中的CO ₂膜渗透性，这可能是由于脂质组成或CO ₂通道蛋白的变化所致。CO ₂膜通透性的变化表明与细胞周围碳酸钙可可脂的密度无关，这可能会阻止化合物的通过。八足植物对CO ₂的膜渗透率略低于硅藻，但通常高于绿藻的膜渗透率。这些测量的一个警告是，用于解释¹⁸ O交换数据假定催化¹⁸ O交换的碳酸酐酶均匀分布在电池中。该假设的含义使用两室模型进行了测试，该模型具有碳酸酐酶的不均匀分布，以模拟^18个O交换数据，然后从模拟数据推断出血浆膜的CO ₂渗透率。该分析表明，推定的血浆膜CO ₂渗透率是最小估计值，但在大多数情况下应相当准确。