STUDY THE PHOTOGRAPH BELOW AND SUMMARIZE THE KEY STEPS IN THE PROCESS OF FORMATION OF STARCH Feedback One glucose molecule is formed only after 6 turns of the Calvin cycle. The 6-carbon molecule first formed by rubisco is unstable and is quickly converted to 2 molecules of PGAL (glyceraldehyde-3-phosphate also known as G3P). PGAL can be returned to the Calvin cycle as RuBP or used in glycolysis and several other anabolic processes to make amino acids or lipids.