Biol. 1311 9/11/06 Hemoglobin’s “work environment” Please note where the Hb doesn’t go (fig 44.1) Organisms have built structures to make use of hemoglobin warts and all Relative to O 2, Hb is big; 32 daltons versus 68,000 O 2 can get through a membrane (in fact many in succession) Big things are expensive to move Cheapskate organisms are successful O 2 is small enough to move by diffusion Diffusion is free So how do you optimize diffusion given that organisms are made of cells? Fick’s law provides guidelines; an equation that isn’t about calculations (fig 44.4) Back to an old friend J (flux rate) = SA X D ( ∆ c)/( ∆ x) SA = surface area D = diffusion coefficient for molecule (=k) ( ∆ c)/( ∆ x) = difference in concentration divided by distance Diffusion works best for short distances Generalizations about tissues again, but more details The nature of hemoglobin requires specific structures to take advantage of its capabilities and limitations Organisms are full of organs made of tissues (Fig 41.3)
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Fig, Fick, Diffusion Diffusion, law Diffusion coefficients