Topic Respiration / Photosynthesis Essay - Main Points!

Q) Distinguish Calvin cycle and Krebs cycle

Main points
Key idea:	Site of occurrence
Calvin cycle: Occurs at stroma of chloroplast  Krebs cycle: Occurs at mitochondrial matrix
Key idea:	Starting material
Calvin cycle: Ribulose bisphosphate (RuBP) ; eventually regenerated Krebs cycle: Oxaloacetate ; eventually regenerated
Key idea:	Substrate
Calvin cycle: CO2 used to convert RuBP to an unstable 6C compound that breaks down to form glycerate-3-phosphate + ref to carbon fixation Krebs cycle: Acetyl-CoA combines w oxaloacetate, to form citrate
Key idea:	Role of CO2
Calvin cycle: CO2 as substrate Krebs cycle: CO2 released due to decarboxylation rx
Key idea:	Role of O2
Calvin cycle: Not required Krebs cycle: Occurs only when O2 present
Key idea:	Electron carriers
Calvin cycle: NADPH as e donors ; to reduce glycerate-3-phosphate to glyceraldehyde-3-phosphate Krebs cycle: NAD+ and FAD as e acceptors ; to oxidize intermediates of cycle
Key idea:	ATP
Calvin cycle: Requires energy throu hydrolysis of ATP Krebs cycle: ATP syn throu substrate level phosphorylation
Key idea:	Products
Calvin cycle: For every 3 mol of CO2 that enter cycle,1 glyceraldehyde-3-phosphate is made Krebs cycle: Gives rise to 2 ATP, 6 NADH, 2 FADH2 per glucose molecule*
Key idea:	Nature of the process
Calvin cycle: Anabolic ; syn of hexose phosphates that give rise to starch Krebs cycle: Catabolic ; oxidation of acetyl-CoA throu a series of decarboxylation +  dehydrogenation rx
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Glyceraldehyde-3-phosphate is a triose phosphate (v) Clarification of worked solution – Each rotation of the Krebs cycle gives rise to 1 ATP, 3 NADH, 1 FADH2. For every glucose oxidized, the cycle rotates twice.