Chapter 24 - Light Independent Reactions and Carbon Concentration

light independent reactions

use ATP and NADPH made in light dependent reactions, do not directly require light

calvin benson cycle (C₃ pathway)

generates a 3 carbon compound by the time it is completed, divided into 3 steps

light independent reactions

use ATP and NADPH made in light dependent reactions, do not directly require light

calvin benson cycle (C₃ pathway)

generates a 3 carbon compound by the time it is completed, divided into 3 steps

carbon fixation

first step of calvin cycle, CO₂ is attached (“fixed”) to a molecule of RuBP catalyzed by rubisco

rubisco

attaches rubisco to CO₂, but sometimes O₂ mistakenly

when CO₂ and RuBP are fixed, what is it converted to?

2 molecules of PGA (3GP)

carbon reduction

converts the 2 PGA into PGAL (G3P), requires ATP and NADPH

what is the purpose of PGAL?

most remain in the cycle, few leave the cycle to make sugars

RuBP regeneration phase

RuBP is made so that the cycle can continue

photorespiration

occurs when rubisco fixes O₂ to RuBP instead of CO₂, results in a net loss of carbon

bundle-sheath cells

CO₂ is concentrated in a separate area from O₂ to prevent photorespiration from occuring

C₄ pathway

CO₂ is fixed to PEP creating oxaloacetate, which then travels to the bundle-sheath cells, the steps of the calvin cycle occur in two different places

where is the C₄ pathway the most efficient?

hot, dry climates

CAM photosynthesis

the different steps of the calvin cycle occur at different times