the main products of the Calvin cycle are six carbon dioxide molecules

Question

this is about light-independent reactions/calvin cycle (dark reactions)

Answer 1

Actually, the Calvin Cycle consumes six CO₂ molecules - but it's not that simple. You might be thinking of the Krebs cycle? Anyway, CO₂ is captured in chloroplasts by a five-carbon molecule called ribulose bisphosphate (abbreviated RuBP) which then forms a six-carbon compound that immediately splits into two 3-carbon compounds (see, I told you it wasn't that simple!). The rest of the Calvin cycle does a couple of things: 1. it "juices up" the carbon in those 3-C compounds so it contains more energy. That carbon may then be used to make glucose (or many carbohydrates), amino acids, lipids, etc. via many different pathways. That energy pumped into carbon came from high-energy electrons captured in NADPH during the light reactions and ATP also made during the light reactions. 2. it recovers the remaining carbons to make that magic 5-carbon RuBP molecule I alluded to earlier. Thus, the Calvin cycle really has three aspects: 1. carbon fixation (capturing that dead, lifeless CO₂ from the atmosphere into molecules in the plant), 2. reduction (which means reducing or making more negative) of carbon using high-energy electrons (which have a negative charge) from NADPH, and 3. regeneration where the remaining carbon is "recycled" to RuBP to accept another CO₂ molecule. The cycle must crank through six times to procure enough carbon for one glucose molecule. It should be noted that the Calvin cycle is incredibly complex and involves multiple rearrangements of several different carbon compounds to arrive at something like glucose; it's not simply "hooking together" 6 CO2 and voila! Here's your glucose!