Triose Phosphate That Leaves the Calvin Cycle Builds Every Carbon Compound a Plant NeedsThe Calvin cycle makes triose phosphate (TP), the three-carbon sugar that feeds the rest of the plant's chemistry.The triose phosphate that leaves the cycle is a versatile building block for many carbon compounds, not just glucose.To build compounds that also contain nitrogen, sulfur or phosphorus, the plant adds mineral nutrients taken up from the soil.Exam techniqueYou are not required to know the detailed steps of these synthesis pathways.You should know that almost every carbon compound in a plant can be traced back to triose phosphate.One Product, Many Uses: What Triose Phosphate BecomesNoteOnly the triose phosphate that is not needed to regenerate RuBP is free to make products.That spare triose phosphate is the starting material for the compounds below.The Main Products Made From Triose PhosphateCarbohydrates: two triose phosphate join to form hexose sugars such as glucose.Glucose is joined into starch for storage or cellulose for cell walls.It can also be converted into sucrose for transport around the plant.Lipids: triose phosphate provides both the fatty acids and the glycerol needed to make triglycerides.These lipids are used for energy storage and for membranes.Amino acids: Calvin cycle intermediates gain nitrogen to form amino acids, which are joined into proteins.Nucleotides: carbon from the cycle combines with nitrogen and phosphorus to build the units of DNA and RNA.Calvin cycleAnalogyTriose phosphate is like a versatile Lego brick.The same brick can be built into sugars, lipids, amino acids or nucleotides.Mineral Nutrients Supply the Atoms Carbon Alone Cannot ProvideTriose phosphate only contains carbon, hydrogen and oxygen.Compounds that also need other elements rely on mineral ions absorbed from the soil.Nitrogen: taken up as nitrate or ammonium ions and added to make amino acids and nucleotides.Phosphorus: taken up as phosphate ions and used in ATP, nucleotides and phospholipids.Sulfur: taken up as sulfate ions and needed for the amino acids cysteine and methionine.NotePlants can make all 20 amino acids they need.This is possible because they can add nitrogen and sulfur to carbon skeletons from the Calvin cycle.Every Carbon Compound in a Plant Traces Back to the Calvin CycleBecause triose phosphate is the shared starting point, all carbon compounds in a plant can be traced back to the Calvin cycle.This makes carbon fixation the foundation for building the whole plant body.AnalogyThink of the Calvin cycle as a factory making one raw material, triose phosphate.Different assembly lines turn that raw material into carbohydrates, lipids, proteins and nucleic acids.Why Plants Do Not Need Amino Acids in Their DietTheory of KnowledgeHumans must eat several amino acids because we cannot make them.How does the plant's ability to make all 20 amino acids change how we define an essential nutrient?Active recallWhich molecule leaving the Calvin cycle is the starting point for making other carbon compounds?Name two carbohydrates and two other types of compound made from triose phosphate.Which element from the soil is needed to make amino acids, and in what ion forms is it absorbed?Why is sulfur needed for protein synthesis in plants?
