BIOL 1000 Chapter Notes - Chapter 7: Photorespiration, Rubisco, Carbon Fixation
29 Oct 2016
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Active site of rubisco is not specific to co2. Rubisco acts as oxygenase when o2 binds; acts as carboxylase when co2 binds. Surface of plants consists waxy cuticle prevents evaporation of water & inhibits co2 flow. Pores on leaves called stomata facilitate movement of gases into/out of leave. Movement of gases is governed by diffusion from high concentration to low: o2 & water diffuses out b/c their concentrations are higher inside leaf, co2 diffuses in b/c concentration inside leave is low. They need to close stomata to conserve water & open stomata to allow co2 in. Plants in hot climates have evolved mode of carbon fixation that minimizes photorespiration. Co2 initially binds to pep (3-c) producing oxaloacetate (4-c), which is reduced to malate. Malate is transported to site of calvin cycle where its converted to pyruvate (3-c), releasing co2. Levels of co2 at site of cycle are higher, which inhibits oxygenation reactions.
