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Light-independent reaction

Light-independent reaction. To be able to explain that: Energy from the light-independent reaction is used to fix carbon dioxide. Write a balanced equation for photosynthesis Give reasons why photosynthesis is important. In which cycle does photosynthesis feature?

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Light-independent reaction

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  1. Light-independent reaction To be able to explain that: • Energy from the light-independent reaction is used to fix carbon dioxide.

  2. Write a balanced equation for photosynthesis Give reasons why photosynthesis is important. In which cycle does photosynthesis feature? What is the waste product of photosynthesis? What is the splitting of water called? What is made during the light dependent reaction? 6CO2 + 6H2O  6O2 + C6H12O6 Makes food, oxygen carbon oxygen photolysis ATP, NADPH, oxygen

  3. The Light-Independent Reactions • The light-independent, or carbon-fixing reactions, of photosynthesis take place in the stroma of the chloroplasts • CO2 readily diffuses into the chloroplast where it is built up into sugars in another cyclic process called the Calvin cyclt

  4. Ribulose biphosphate (RuBP) glycerate 3-phosphate (GP) ribulose bisphosphate carboxylase 5 carbon sugar A 3 carbon compound (an acid) An enzyme also known as RuBISCO Glossary

  5. The fixation of Carbon Dioxide is light independent. Carbon Dioxide combines with RuBP = 2 x glycerate 3 phosphate • CO2 is covalently bonded to RuBP catalysed by the enzyme RuBISCO • The product is two molecules of glycerate 3 phosphate • This process is called fixation  CO2 RuBP

  6. Energy and H+ ions are required to turn the Glycerate 3 phosphate into the 3 carbon sugar triose phosphate Energy is provided by ATP and the H+ ion is provided by the NADPH from the light dependant reaction 2NADPH 2NADP 2ADP + Pi 2ATP = 2 x glycerate 3 phosphate 2 x Triose Phosphate  CO2 RuBP

  7. Two triose phosphate molecules join together to form one hexose sugar e.g. glucose Glucose may be immediately respired, stored as starch or converted into other products The bulk of triose phosphate is converted into more RuBP to enable the fixation of Carbon to continue This uses the rest of the ATP produced in the light dependant reaction 2NADPH 2NADP 2ADP + Pi 2ATP = 2 x glycerate 3 phosphate 2 x Triose Phosphate  CO2 RuBP ADP + Pi Hexose sugar ATP

  8. Plants can’t ingest proteins and fats Calvin cycle is the starting point for all the substances a plant needs • 5 out of every 6 molecules of triose phosphate are used to regenerate RuBP

  9. Calvin cycle in summary • CO2 combines with ribulose bisphosphate • Glycerate phosphate is made • Glycerate phosphate is converted into triose phosphate • Triose phosphate is converted into glucose • RuBP is regenerated

  10. Which compound is carboxylated? How is carbon dioxide fixed? What does GP stand for? Which compound is regenerated? What is ATP required for? What is NADPH required for? What reaction converts GP into triose phosphate? What kind of sugar is RuBP? Which enzyme is important in the Calvin Cycle? How many carbon atoms in GP? Where does the Calvin Cycle happen? RuBP Joined to RuBP Glycerate-3-phosphate RuBP Energy for reduction and regeneration of RuBP Source of hydrogen for reduction reduction pentose Rubisco 3 stroma Questions

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