Question

ases of the Calvin cycle, Total: 17 marks 23. Describe the main events occurring inside each of the three phases of the Calul using the acronyms of the molecules, enzymes, and energy carriers involved. (9 marks: 3 marks for each phase)

Answer 1

3 phases of Calvin cycle are eleborately described with acronyms of the molecules, enzymes and energy carriers in the following images
Calvin cycle also known as a cycle or neductive pentose phosphate cycle, by this cycle coa reduced to three carbon sugar througa series of biochemical suaction. Calvin cycle takes place in stroma of Chloroplasts i eukaryotic photosynthetic onganism, it also occured în cytosol wease of prokaryotic photocynthetic organisme. the reaction of calvin cycle can be divided into a phases? 1. Carboxylation, 2. Reduction, a: Regeneration' Carboxylation i In this phase, coz is mearporated into 5 carbon compound Rubip (Ribulose-1,5-bisphosphate). This step is catalyzed by Rubislo (Ribulose-1,5- bisphosphate carboxylase orygenase). As a product of this reaction is 6C containing intermediate Eredio late which is immediately splitled into le molecules of s phosphogy errate ( 3PGA on glycerate-3-phosphate). Therefore, for every 3 molecules of coz that enter the cycle and 6 molecules of 3 PGA is formed. CH₂OP CH₂OP c-OH C-014 H-I-OH H-(-OH CHOP CHOP CH₂OP CH₂OP H-c-oh RuBP Enediolate Rearboxy 3.keto гоон intermediate Darabinitol 1,5 3 PGA bisphosphate Reduction: - It is the next phase of the cycle, in this reaction 3 PGA is reduced into glyceraldehyde-3-phosphate. At first, 3PGA is phosphorylated by me ate molecule to form 1,3- bisphosphoglycrate. This step is catalyzed by phosphoglyurate kinase. Then, 1,3-bisphos- -phoghyeerate is reduced by NADPI and this step is eatalupydbou glycraldehyde-8-phosphate dehydrogenase to forom one moleculo of glyceraldehyde- 3-phosphate, Thuis, 6 niolecules of ATP are to phosphorylate Gmidlecules of 3-PGA to 1,3-bisphosphoglycrate CHOP OP Н-С - ОН c=0 COOH Co. Ho-c-coo H₂O Hé-OH H-&-04

and 6 molecules of NADPH are required to reduce 6 mokoules of 1,3- bisphosphoqlyecrate to glycinaldehyde- 3-phosphate. CH₂OP OP H -OH AP N (-OH ADPH CHO - -OH H- COOH ChOP. - 3. Phosphoglycerate CH₂OP 1, 3- bisphospho. Colyceraldehyde-3-phosphate. glycerate Regeneration : Met production of fixed carbon in Calvin cycle is one mokeute of glyceraldehyde-3-phosphate. Other å molecules of dyciraldehyde a phosphate are processed as remainder of Calvin cycle reactions to regenerate 3molecules of RuBP. This is a series of reactions, The intermediates in this pathway include 3, 4, 5, 6 and 7 e sugars. Czt egtu ezt fech Cz+q otly 5 € 395 R5P BATP GBADP C5105 RuBP] ROP GAP + FTP B-17P DHAP] + [E4P) qez cur GAPI 3PGA GATP 1x5Ples GADP 11,3 bisPGA + FUPI, F1, 6Р. .GNADPH YGNADP + P: DHAp+GAP plz IGAP DHAP

SMN Summary of C3 Cycle 34002 3 X RuBP P ochovulation 6X 3 PGA GATP 3 ADP 96ADP 'Calvin' ucle 6x1,3 bisphosphoglycerate NADPH 1 Regeneration Reduction Go 5 4 GBP 6X G3P 3 ATP I NADP iX GBP This is Calvin Cycle, consist of a phases, Carboxylation ! Fixation of carbon by carbosylation of Rube Reduction : Reduction of fixed carbon to start the synthesis of triose phosphate. Regeneration. It is the synthesis of RuBP (starting compourd) for, amolecules of RuBP (3*5=15C) are carboxylated, eleared, phosphorylated, suduced and dephosphomylated, 6 mol of G3P are produced (6 X 3 = 18 C). Of these, one G3P (3C) exits the pathisay wo a product and- 5 mol of 63 P are (5x3 =154) are roycled back into 3 mol of 5C RuBP (3x5 215 6) Regeneration of RuBP is an active process. To regenerate Ind of RuBP, 1 mol of ATP is required. Thus, total 3 mol of ATP are required to regeourate 3 mol of RuBP. As ar summary for the net synthesis of one mol of GBP, calvin cycle consumes total g mol of ATP and 6 mol of NADPH. 300, + 6NADPH + ATP C3P + 6 NADP+ +9) ADP.

RuBP - Ribulose-1, 5 bisphosphate 3 PG1A - 3 Phosphoglycerate /alycrate-3-phosphate Rubis Co- Ribulose -1,5-bisphosphală carboxylase GAP/GBP - Glyceraldehyde 3 phosphate Rap - Ribose-5-phosphate E4P - Brythoose-4 - phosphate X5p - Xylulose-5-phosphate. 57.P - sedoheptelose - 7-phosphate 3-1,7-P- Sedo keptulose-1, 1- bisphosphate DHAP - Bihydroxy acetone phosphate F6P - Fructose-6-phosphate. F-1, 6-P-Fructose-1, 6-bisphosphate