Photosynthesis The Calvin Cycle Life from Air AP

Photosynthesis: The Calvin Cycle Life from Air AP Biology Modified from Kim Foglia 2006 -2007

Monday, November 21 st: Happy Monday, AP BIO! Today we will: 1. Compare the Dark reactions with the light reactions of Ps. 2. Compare and contrast the processes of cell respiration and Ps. ** TEST is tomorrow, Tuesday. AP Biology

ETC of Photosynthesis § ETC produces from light energy u ATP & NADPH § go to Calvin cycle § PS II absorbs light u u u AP Biology excited electron passes from chlorophyll to “primary electron acceptor” need to replace electron in chlorophyll enzyme extracts electrons from H 2 O & supplies them to chlorophyll § splits H 2 O § O combines with another O to form O 2 § O 2 released to atmosphere § and we breathe easier!

Remember what it means to be a plant… § Need to produce all organic molecules necessary for growth u carbohydrates, lipids, proteins, nucleic acids § Need to store chemical energy (ATP) produced from light reactions in stable form u can be moved around plant u saved for a rainy day u AP Biology

Autotrophs § Making energy & organic molecules from light energy u photosynthesis carbon + water + energy glucose + oxygen dioxide 6 CO 2 + 6 H 2 O + light C 6 H 12 O 6 + 6 O 2 energy AP Biology

Light reactions § Convert solar energy to chemical energy u ATP energy u NADPH reducing power § What can we do now? build stuff !! AP Biology

How is that helpful? § Want to make C 6 H 12 O 6 synthesis u How? From what? What raw materials are available? u CO 2 carbon fixation NADPH NADP C 6 H 12 O 6 AP Biology reduce CO 2 NADP

From CO 2 C 6 H 12 O 6 § CO 2 has very little chemical energy u fully oxidized § C 6 H 12 O 6 contains a lot of chemical energy reduced u endergonic u § Reduction of CO 2 C 6 H 12 O 6 proceeds in many small uphill steps each catalyzed by specific enzyme u using energy stored in ATP & NADPH u AP Biology

From Light reactions to Calvin cycle § Calvin cycle u chloroplast stroma § Need products of light reactions to drive synthesis reactions ATP u NADPH u AP Biology

Calvin cycle 1 C 3. Regeneration of Ru. BP starch, sucrose, cellulose & more Ru. BP ribulose bisphosphate 3 ATP 3 ADP used to make glucose 5 C CO 2 Rubisco ribulose bisphosphate carboxylase 6 C glyceraldehyde-3 -P G 3 P 3 C PGA phosphoglycerate 6 NADPH 6 NADP 3 C 6 ATP 2. Reduction AP Biology 1. Carbon fixation 3 C 6 ADP

Remember G 3 P? glucose C-C-C-C 2 ATP 2 ADP glycolysis fructose-6 P P-C-C-C-P DHAP G 3 P P-C-C-C-P pyruvate AP Biology C-C-C 2 NAD+ 2 NADH 4 ADP 4 ATP

Calvin Cycle Stroma of chloroplast Carbon dioxide (CO 2) Rubisco Ribulose 1, 5 -bisphosphate (Ru. BP) (5 C) 3 -phosphoglycerate (3 C) (PGA) Carbon fixation 3 ADP 6 ADP Reforming Ru. BP 3 ATP 1, 3 -bisphoglycerate (3 C) 6 NADPH 2 Pi Reverse of glycolysis Glyceraldehyde 3 -phosphate (3 C) Glucose and other sugars 6 NADP+ 6 Pi Glyceraldehyde 3 -phosphate (3 C) (G 3 P) AP Biology 6 ATP

The Calvin Cycle AP Biology

To G-3 -P and Beyond! § Glyceraldehyde-3 -P end product of Calvin cycle u energy rich 3 carbon sugar u “C 3 photosynthesis” u § G-3 -P = important intermediate § G-3 -P glucose carbohydrates AP Biology lipids amino acids nucleic acids

Rubisco § Enzyme which fixes carbon from air ribulose bisphosphate carboxylase u the most important enzyme in the world! u § it makes life out of air! u AP Biology definitely the most abundant enzyme

Accounting § The accounting is complicated u 3 turns of Calvin cycle = 1 G 3 P u 3 CO 2 1 G 3 P (3 C) u 6 turns of Calvin cycle = 1 C 6 H 12 O 6 (6 C) u 6 CO 2 1 C 6 H 12 O 6 (6 C) u 18 ATP + 12 NADPH 1 C 6 H 12 O 6 u AP Biology any ATP left over from light reactions will be used elsewhere by the cell

Photosynthesis summary § Light reactions produced ATP u produced NADPH u consumed H 2 O u produced O 2 as byproduct u § Calvin cycle consumed CO 2 u produced G 3 P (sugar) u regenerated ADP u regenerated NADP u AP Biology ADP NADP

Summary of photosynthesis 6 CO 2 + 6 H 2 O + light C 6 H 12 O 6 + 6 O 2 energy § § § § § Where did the CO 2 come from? Where did the CO 2 go? Where did the H 2 O come from? Where did the H 2 O go? Where did the energy come from? What’s the energy used for? What will the C 6 H 12 O 6 be used for? Where did the O 2 come from? Where will the O 2 go? What else is involved…not listed in this equation? AP Biology

Supporting a biosphere § On global scale, photosynthesis is the most important process for the continuation of life on Earth each year photosynthesis synthesizes 160 billion tons of carbohydrate u heterotrophs are dependent on plants as food source for fuel & raw materials u AP Biology

The poetic perspective… § All the solid material of every plant § was built by sunlight out of thin air All the solid material of every animal was built from plant material Then all the cats, dogs, rats, people & elephants… are really strands of air woven together by sunlight! AP Biology