Life in the Open Ocean. Joseph J. Torres

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Life in the Open Ocean - Joseph J. Torres


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for A4‐LDH orthologs for differently thermally adapted vertebrates: Antarctic and South American notothenioid fishes, a barracuda fish (Sphyraena ideastes), to goby fishes (Gillichthys mirabilis and G. seta), and the desert iguana (Dipsosaurus dorsalis). Thick line segments indicate approximate ranges of body temperatures of the species.

      Source: Hochachka and Somero (2002), figure 7.7 (p. 312). Reproduced with the permission of Oxford University Press.

      Lipids and Temperature

      We have just been looking at the properties of intermediary metabolic enzymes and observing that changes were needed in enzyme structure to preserve functionality in the face of temperature change. Similarly, the proper environment within the cell with respect to substrates, cofactors, ionic concentrations, and all other properties must be maintained by the cell membrane as temperature changes. The cell membrane itself and its associated proteins govern what crosses it, how much, and the direction of net movement. Ultimately, the cell membrane is the biological barrier that allows the cell its limited autonomy. As a barrier, the membrane not only limits diffusion inward and outward but it also contains embedded transport proteins. The membrane’s effectiveness as a barrier and as a center for transport is highly dependent on temperature.

Schematic illustration of the relationship between the catalytic rate constant (Kcat) and adaptation temperature for A4-LDH orthologs from differently thermally-adapted vertebrates.

      Source: Hochachka and Somero (2002), figure 7.3 (p. 302). Reproduced with the permission of Oxford University Press.

      A Membrane Primer

Schematic illustration of membrane structure.

      Other mechanisms exist for adjusting the fluidity in biomembranes over the short term (hours to days to weeks) in addition to the change in lipid classes just described. Such


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