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8-3 The Reactions of Photosynthesis

8-3 The Reactions of Photosynthesis. Objectives:. Describe the structure and function of a chloroplast . Describe what happens in the light-dependent reactions . Explain what the Calvin Cycle is . Identify factors that affect the rate at which photosynthesis occurs. Inside a Chloroplast.

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8-3 The Reactions of Photosynthesis

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  1. 8-3 TheReactions of Photosynthesis

  2. Objectives: • Describe the structure and function of a chloroplast. • Describe what happens in the light-dependent reactions. • Explain what the Calvin Cycle is. • Identify factors that affect the rate at which photosynthesis occurs.

  3. Inside a Chloroplast • Inside a Chloroplast • In plants, photosynthesis takes place inside chloroplasts. Plant Chloroplast Plant cells

  4. Inside a Chloroplast • Chloroplasts contain thylakoids—saclike photosynthetic membranes. Single thylakoid Chloroplast

  5. Inside a Chloroplast • The reactions of photosynthesis include: the light-dependent reactions and the light-independent reactions, or Calvin cycle. • The light-dependent reactions take place within the thylakoid membranes. • The Calvin cycle takes place in the stroma, which is the region outside the thylakoid membranes.

  6. Inside a Chloroplast CO2 H2O Light NADP+ ADP + P Light- dependent reactions Calvin cycle Calvin Cycle Chloroplast Sugars O2

  7. Electron Carriers • Electron Carriers • When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy. • Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules. • These high-energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose.

  8. Electron Carriers • One of these carrier molecules is a compound known as NADP+ (nicotinamide adenine dinucleotide phosphate). • NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+). • This converts NADP + into NADPH. • NADPH can then carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell.

  9. Light-Dependent Reactions The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.

  10. The Calvin Cycle The Calvin Cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.

  11. Factors Affecting Photosynthesis • Many factors affect the rate of photosynthesis, including: • Water • Temperature • Intensity of light

  12. 8-3 Section Assessment • Summarize the light-dependent reactions. • What reactions make up the Calvin Cycle? • What is the function of NADPH? • What factors affect photosynthesis?

  13. 8-3 Section AssessmentAnswers • The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH. • The Calvin Cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars. • The main function of MADPH is to carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell. • Factors that affect photosynthesis are water, temperature, and intensity of light.

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