Closed stomates Closed stomates lead to… –O 2 builds up  from light reactions –CO 2 is depleted  in Calvin cycle causes problems in Calvin Cycle

Inefficiency of Rubisco: CO 2 vs O 2 Rubisco in Calvin cycle –carbon fixation enzyme normally bonds C to RuBP building sugars –when O 2 concentration is high Rubisco bonds O to RuBP O 2 is alternative substrate breakdown sugars photosynthesis photorespiration Rubisco = ribulose bisphosphate carboxylase / oxygenase

Oxygen Concentration

6C unstable intermediate 1C CO 2 Calvin cycle review 5C RuBP 3C PGA ADP ATP 3C NADP NADPH ADP ATP G3P to make glucose Rubisco 3C G3P C3 plants

Calvin cycle with O 2 5C RuBP Rubisco 3C 2C lost as CO 2 without making ATP photorespiration O2O2 A good enzyme, gone BAD! PGA phosphoglycolate Impact of Photorespiration: Oxidation of RuBP loss of carbons  CO2 reduces production of photosynthesis

Reducing photorespiration Separate carbon fixation from Calvin cycle –C4 plants physically separate carbon fixation from actual Calvin cycle different enzyme to capture CO 2 –PEP carboxylase stores carbon in 4C compounds different leaf structure –CAM plants separate carbon fixation from actual Calvin cycle by time of day fix carbon (capture CO 2 ) during night –store carbon in organic acids perform Calvin cycle during day

C4 plants A better way to capture CO 2 –1st step before Calvin cycle, fix carbon with enzyme PEP carboxylase store as 4C compound –adaptation to hot, dry climates have to close stomates a lot –sugar cane, corn, other grasses…

PEP carboxylase O2O2 light reactions PEP carboxylase enzyme –higher affinity for CO 2 than O 2 (better than Rubisco) –fixes CO 2 in 4C compounds –regenerates CO 2 in inner cells for Rubisco phosphoenolpyruvate (3C) + CO 2  oxaloacetate (4C)

C4 photosynthesis CO 2 O2O2 O2O2 Outer cells –light reaction & carbon fixation –pumps CO 2 to inner cells –keeps O 2 away from inner cells away from Rubisco Inner cells –Calvin cycle –glucose to veins Physically separated C fixation from Calvin cycle

CAM ( Crassulacean Acid Metabolism ) Different adaptation to hot, dry climates –separate carbon fixation from Calvin cycle by time –at night, open stomates & fix carbon in “storage” compounds organic acids: malic acid, isocitric acid –in day, close stomates & release CO 2 from “storage” compounds to Calvin cycle increases concentration of CO 2 in cells –succulents, some cacti, pineapple It’s all in the timing!

CAM plants

C4 vs CAM Summary C4 plants separate 2 steps of C fixation anatomically in 2 different cells CAM plants separate 2 steps of C fixation temporally at 2 different times solves CO 2 / O 2 gas exchange vs. H 2 O loss challenge

CR & Photo Review Mrs. Confrey

Lab 4 Conclusions –Pigments pigments move at different rates based on solubility in solvent –Photosynthesis light & unboiled chloroplasts produced highest rate of photosynthesis

Lab 5: Cellular Respiration using respirometer to measure rate of O 2 consumed Conclusions –  temp =  respiration

Cellular Respiration

How does ATP transfer energy? P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O ATP  ADP –releases energy –can fuel other reactions Phosphorylation –released P i can transfer to other molecules ADPATP Can’t store ATP  too reactive  transfers P i too easily  only short term energy storage  carbohydrates & fats are long term energy storage

Cellular Respiration

Glycolysis summary endergonic invest some ATP exergonic harvest a little ATP & a little NADH yield 2 ATP 2 NADH like $$ in the bank 4ATP ENERGY INVESTMENT ENERGY PAYOFF G3P C-C-C-P NET YIELD

10 reactions –convert glucose (6C) to 2 pyruvate (3C) –produces: 4 ATP & 2 NADH –net: 2 ATP & 2 NADH glucose C-C-C-C-C-C fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P pyruvate C-C-C Glycolysis Overview DHAP = dihydroxyacetone phosphate G3P = glyceraldehyde-3-phosphate ATP 2 ADP 2 ATP 4 ADP 4 NAD Pi2Pi enzyme 2Pi2Pi 2H2H

Alcohol Fermentation 1C 3C2C pyruvate  ethanol + CO 2 NADHNAD +  Regenerates NAD  can’t reverse the reaction Bacteria yeast Alcohol production

 Reversible process  With O 2, lactate is converted back to pyruvate by the liver Lactic Acid Fermentation pyruvate  lactic acid 3C NADHNAD +  O2O2 Animals anaerobic exercise (no O2) Muscle cells Acid lowers pH of cells (cramping)

Kreb’s (citric acid) cycle Acetyl CoA  CO 2 2 ATP! electron carriers –6 NADH –2 FADH 2 –go to ETC! 2 NADH, 2 CO2 2 Pyruvate

oxidative phosphorylation O2O2

Photosynthesis

ETC of Photosynthesis 6 5 $$ in the bank… reducing power to the Calvin Cycle electron carrier

PGA

Photophosphorylation noncyclic photophosphorylation cyclic photophosphorylation

STUDY!!