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Lecture 9

Biology Lecture 9 Outcomes

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Biology 1002B
Tom Haffie

Lecture 9 Carbon Fixation 105 Gt/year of Co2 fixations occurs  Turning CO2 into organic forms  Terrestrial 56.4 Gt  Oceanic 48.5 Gt o Caused by plankton  Photosynthetic areas are around the poles  However most of the organisms are ectoherms (external temperature dictates internal)  So why isn’t there photosynthetic activity in the warm regions Factor Influencing Phytoplankton Distribution  Temperature, sunlight, nutrients  Role: CO2 fixation  Limiting factor: o Iron o It’s a cofactor Southern Ocean Iron release Experiment  Experiment dumps iron into the ocean to see what affects the have on phytoplankton  Results: chlorophyll concentration increases  CO2 fixation increases Calvin Cycle  Light independent, second state of photosynthesis  CO2 O2 1:1 stoichiometric ratio  Energy from e- converts inorganic CO2 organic o 5 G3P go back to make RuBP o 1 G3P goes to make sugars ( 2 make glucose) Respiration versus photosynthesis  ATP created in chloroplast stay there and reduce C02glucose o Used in endergonic process  Then glucose in mitochondria creates ATP for energy o Fuels cellular processes  Measure respiration by either o CO2 production o O2 consumption  Measure Photosynthesis by o CO2 consumption o O2 production Measuring Carbon Fixation  Elysia are put in CO2 analyzer  CO2 fixation rate ( umol C/ chlorophyll/sec ) o Rate at which inorganic CO2 organic molecules Light Saturation Curve  In the darkno light rxnno NADPH fixationno photosynthesis o CO2 fixation is negative o Elysia I converting sugar into CO2 o Its respiring  When the light is turned on, fixation rate increases  Reaches Light compensation point: CO2 fixation rate= 0  Rate mitochondria is releasing CO2=rate Calvin cycle is using CO2  Elysia has a net 0 fixation rate at 170  To grow, you have to be above this threshold  At saturation point: turnover rate of Calvin cycle (enzymes) reach its max O2 can compete with CO2  Rubisco o Carboxylating enzyme o Integrates CO2 into RuBP  Is ancient (3bya)  Both O2 and CO2 can enter the active site o 3bya there
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