Many high school biology tutorial materials express the transfer pathway of photosynthesis dark reaction carbon atoms as:
CO2→C3→C5
Is that correct?
Let's take a look at the chemical reaction process of the Calvin cycle:
Calvin Cycle Phase I Reaction
1,5-Ribulose diphosphate, abbreviated RuBP in English, is the C5 in high school textbooks. It is first enol allogeneic, then carboxylated, and then hydrolyzed to give 2 molecules of 3-phosphoglycerol. The green circle in the figure is the carbon atom in the CO2 added to C5, and the blue arrow represents the hydrolyzed chemical bond.
The next reaction is as follows:
Calvin loop steps
3-phosphoglycetic acid→ 3-phosphoglycetic acid, no change in number and position of C atoms occurs.
12 molecules 3 glyceraldehyde phosphate, divided into 2 parts. A portion (2 molecules) is used to synthesize glucose or transport it into the cytoplasm to synthesize sucrose; the other 10 molecules are used to supplement depleted RuBP.
From the above reaction process, it can be seen that the carbon atoms in carbon dioxide are entirely possible to enter the 10 molecules of 3-phosphoglycerin, which is composed of the carbon chain of RuBP.