The CO 2 fixing enzyme is called ribulose 15 bisphosphate

The co 2 fixing enzyme is called ribulose 15

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The CO 2 -fixing enzyme is called ribulose 1,5-bisphosphate carboxylase/oxygenase ( rubisco ). Rubisco is found in all photosynthetic organisms that use the Calvin cycle to fix carbon, and is thought to be the most abundant enzyme on Earth. Rubisco is inefficient because although it does catalyze the addition of CO 2 to RuBP, it also catalyzes the addition of O 2 to RuBP. Photorespiration Oxygen and carbon dioxide compete at the enzyme’s active sites, which slows the rate of CO 2 reduction. When O 2 and RuBP react in rubisco’s active site, one of the products undergoes a process called photorespiration . Photorespiration “undoes” photosynthesis because it consumes energy and releases fixed CO 2 . When photorespiration occurs, the rate of photosynthesis declines drastically. Carbon fixation is favoured over photorespiration when a cell’s CO 2 concentration is high and O 2 concentration is low. Carbon Dioxide Enters/Leaves Through Stomata Stomata are leaf structures where gas exchange occurs. They consist of two guard cells that change shape to open or close. When a leaf’s CO 2 concentration is low during photosynthesis, stomata open to allow atmospheric CO 2 to diffuse into the leaf and its cells’ chloroplasts. A strong concentration gradient favouring entry of CO 2 is maintained by the Calvin cycle, which constantly uses up the CO 2 in chloroplasts.
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