Triose phosphate (TP) is the three-carbon sugar produced in the Calvin cycle when GP is reduced using ATP and reduced NADP. It is the starting point for almost every organic molecule in the plant.For every 6 molecules of TP produced, 5 are used to regenerate RuBP, using ATP, so that the cycle can continue. Only 1 molecule leaves the cycle as product.Worked example: One glucose molecule has 6 carbon atoms, so 2 TP must leave the cycle. Only 1 in 6 TP molecules leaves, so 12 TP must be made. Each turn of the cycle fixes one CO2 and makes 2 TP, so this needs 6 turns, fixing 6 CO2.TP that leaves the cycle is used to make:• Hexose sugars such as glucose, from two TP molecules. Glucose is used in respiration, or joined to make sucrose for transport, starch for storage and cellulose for cell walls.
• Lipids: TP is converted to glycerol, and GP is converted to fatty acids. These join to form triglycerides and phospholipids.
• Amino acids, made from GP or TP with nitrogen added from nitrate ions absorbed from the soil. Amino acids are joined to make proteins.
• Nucleotides for DNA and RNA, which also need nitrate and phosphate ions from the soil.So plants need mineral ions as well as the products of photosynthesis: carbon, hydrogen and oxygen come from TP, but nitrogen and phosphorus must come from the soil.
• Lipids: TP is converted to glycerol, and GP is converted to fatty acids. These join to form triglycerides and phospholipids.
• Amino acids, made from GP or TP with nitrogen added from nitrate ions absorbed from the soil. Amino acids are joined to make proteins.
• Nucleotides for DNA and RNA, which also need nitrate and phosphate ions from the soil.So plants need mineral ions as well as the products of photosynthesis: carbon, hydrogen and oxygen come from TP, but nitrogen and phosphorus must come from the soil.