Chapter 16 lecture 2

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  • So, in effect, photosynthesis is respiration run backwards powered by light.
  • CO 2 contains little energy because it is fully oxidized Reduce CO 2 in a series of steps to synthesize a stable energy storage molecule
  • RuBP = ribulose bisphosphate Rubisco = ribulose bisphosphate carboxylase
  • Gluconeogenesis == making new glucose
  • Chapter 16 lecture 2

    1. 1. Photosynthesis: The Calvin Cycle Life from Air
    2. 2. The Calvin Cycle Whoops! Wrong Calvin…
    3. 3. Remember what it means to be a plant… <ul><li>Need to produce all organic molecules necessary for growth </li></ul><ul><ul><li>carbohydrates, lipids, proteins, nucleic acids </li></ul></ul><ul><li>Need to store chemical energy produced from light reactions </li></ul><ul><ul><li>in stable form </li></ul></ul><ul><ul><li>can be moved around plant </li></ul></ul><ul><ul><li>saved for a rainy day </li></ul></ul>
    4. 4. Autotrophs <ul><li>Making energy & organic molecules from light energy </li></ul><ul><ul><li>photosynthesis </li></ul></ul>+ water + energy  glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  + + +
    5. 5. Light reactions <ul><li>Convert solar energy to chemical energy </li></ul><ul><ul><li>ATP </li></ul></ul><ul><ul><li>NADPH </li></ul></ul><ul><li>What can we do now? </li></ul> energy  reducing power   build stuff !!
    6. 6. How is that helpful? <ul><li>Want to make C 6 H 12 O 6 </li></ul><ul><ul><li>synthesis </li></ul></ul><ul><ul><li>How? From what? What raw materials are available? </li></ul></ul>CO 2 C 6 H 12 O 6 NADPH NADP reduce CO 2 carbon fixation NADP
    7. 7. From CO 2  C 6 H 12 O 6 <ul><li>CO 2 has very little chemical energy </li></ul><ul><ul><li>fully oxidized </li></ul></ul><ul><li>C 6 H 12 O 6 contains a lot of chemical energy </li></ul><ul><ul><li>reduced </li></ul></ul><ul><ul><li>endergonic </li></ul></ul><ul><li>Reduction of CO 2  C 6 H 12 O 6 proceeds in many small uphill steps </li></ul><ul><ul><li>each catalyzed by specific enzyme </li></ul></ul><ul><ul><li>using energy stored in ATP & NADPH </li></ul></ul>
    8. 8. From Light reactions to Calvin cycle <ul><li>Calvin cycle </li></ul><ul><ul><li>chloroplast stroma </li></ul></ul><ul><li>Need products of light reactions to drive synthesis reactions </li></ul><ul><ul><li>ATP </li></ul></ul><ul><ul><li>NADPH </li></ul></ul>
    9. 9. starch, sucrose, cellulose & more Calvin cycle RuBP Rubisco 1. Carbon fixation 2. Reduction 3. Regeneration of RuBP ribulose bisphosphate ribulose bisphosphate carboxylase used to make glucose G3P glyceraldehyde-3-P PGA phosphoglycerate C C C 1C CO 2 5C 3C 6 NADP 6 NADPH 6 ADP 6 ATP 3 ADP 3 ATP 3C 3C C C C C C C C C C C C C C C C 6C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C = = | H | H | H | H | H | H C C C – –
    10. 10. glucose C-C-C-C-C-C fructose-6P P- C-C-C-C-C-C -P DHAP P- C-C-C G3P C-C-C -P pyruvate C-C-C 2 ATP 2 ADP Remember G3P? glycolysis 2 NAD + 2 NADH 4 ADP 4 ATP
    11. 11. Calvin Cycle Glyceraldehyde 3-phosphate (3C) (G3P) Glucose and other sugars Ribulose 1,5-bisphosphate (RuBP) (5C) 3-phosphoglycerate (3C) (PGA) Glyceraldehyde 3-phosphate (3C) Glyceraldehyde 3-phosphate (3C) (G3P) Rubisco Reforming RuBP Reverse of glycolysis Carbon fixation Stroma of chloroplast Carbon dioxide (CO 2 ) 6 NADPH 3 ATP 3 ADP 6 ATP 6 ADP 6 NADP + 2P i 1,3-bisphosphoglycerate (3C) 6P i
    12. 12. To G-3-P and Beyond ! <ul><li>Glyceraldehyde-3-P </li></ul><ul><ul><li>end product of Calvin cycle </li></ul></ul><ul><ul><li>energy rich 3 carbon sugar </li></ul></ul><ul><ul><li>“ C3 photosynthesis ” </li></ul></ul><ul><li>G-3-P = important intermediate </li></ul><ul><li>G-3-P   glucose   carbohydrates </li></ul><ul><ul><li>  lipids </li></ul></ul><ul><ul><li>  amino acids </li></ul></ul><ul><ul><li>  nucleic acids </li></ul></ul>
    13. 13. Rubisco ** test question in 2011 test, had to know actual name <ul><li>Enzyme which fixes carbon from air </li></ul><ul><ul><li>ribulose bisphosphate carboxylase </li></ul></ul><ul><ul><li>the most important enzyme in the world! </li></ul></ul><ul><ul><ul><li>it makes life out of air! </li></ul></ul></ul><ul><ul><li>definitely the most abundant enzyme </li></ul></ul>
    14. 14. Accounting <ul><li>The accounting is complicated </li></ul><ul><ul><li>3 turns of Calvin cycle = 1 G3P </li></ul></ul><ul><ul><li>3 CO 2  1 G3P (3C) </li></ul></ul><ul><ul><li>6 turns of Calvin cycle = 1 C 6 H 12 O 6 (6C) </li></ul></ul><ul><ul><li>6 CO 2  1 C 6 H 12 O 6 (6C) </li></ul></ul><ul><ul><li>18 ATP + 12 NADPH  1 C 6 H 12 O 6 </li></ul></ul><ul><ul><li>any ATP left over from light reactions will be used elsewhere by the cell </li></ul></ul>
    15. 15. Photosynthesis summary <ul><li>Light reactions </li></ul><ul><ul><li>produced ATP </li></ul></ul><ul><ul><li>produced NADPH </li></ul></ul><ul><ul><li>consumed H 2 O </li></ul></ul><ul><ul><li>produced O 2 as byproduct </li></ul></ul><ul><li>Calvin cycle </li></ul><ul><ul><li>consumed CO 2 </li></ul></ul><ul><ul><li>produced G3P (sugar) </li></ul></ul><ul><ul><li>regenerated ADP </li></ul></ul><ul><ul><li>regenerated NADP </li></ul></ul>NADP ADP
    16. 16. Summary of photosynthesis <ul><li>Where did the CO 2 come from? </li></ul><ul><li>Where did the CO 2 go? </li></ul><ul><li>Where did the H 2 O come from? </li></ul><ul><li>Where did the H 2 O go? </li></ul><ul><li>Where did the energy come from? </li></ul><ul><li>What’s the energy used for? </li></ul><ul><li>What will the C 6 H 12 O 6 be used for? </li></ul><ul><li>Where did the O 2 come from? </li></ul><ul><li>Where will the O 2 go? </li></ul><ul><li>What else is involved…not listed in this equation? </li></ul>6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  + + +
    17. 17. Supporting a biosphere <ul><li>On global scale, photosynthesis is the most important process for the continuation of life on Earth </li></ul><ul><ul><li>each year photosynthesis synthesizes 160 billion tons of carbohydrate </li></ul></ul><ul><ul><li>heterotrophs are dependent on plants as food source for fuel & raw materials </li></ul></ul>
    18. 18. The poetic perspective… <ul><li>All the solid material of every plant was built by sunlight out of thin air </li></ul><ul><li>All the solid material of every animal was built from plant material </li></ul>Then all the cats, dogs, rats, people & elephants… are really strands of air woven together by sunlight! sun air
    19. 21. Any Questions??

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