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Understanding Photosynthesis Process: Light Reactions and Calvin Cycle

Explore the complex process of photosynthesis, involving light-dependent reactions in chloroplasts and the Calvin Cycle, essential for plants to produce sugars for energy. Learn about autotrophs and heterotrophs in relation to photosynthesis. Discover the role of chlorophyll and electron carriers in converting sunlight into chemical energy. Follow the steps of photosynthesis and understand how plants utilize sunlight to create oxygen and carbohydrates. Enhance your knowledge of this vital biological process!

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Understanding Photosynthesis Process: Light Reactions and Calvin Cycle

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  1. Photosynthesis Chapter 8

  2. Autotrophs vs. Heterotrophs • Autotrophs: Plants and some other types of organisms that use light energy from SUNLIGHT to make their own food. These organisms undergo photosynthesis!! • – EX: Trees, grass, algae, plants • Heterotrophs: Organisms that CANNOT use the sun’s energy to make food– they obtain energy from the foods they consume • – EX: Deer, rabbits, bear, fish, insects, etc…

  3. The Photosynthesis Equation • Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen • 6CO2 + 6H2O + light→C6H12O6 + 6O2 • (carbon dioxide + water + light → sugars + oxygen) • Plants then use the sugars to produce complex carbohydrates such as starches • Plants obtain CO2 from the air or water in which they grow

  4. Photosynthesis Light Energy Chloroplast CO2 + H2O Sugars + O2

  5. Inside a Chloroplast • Chloroplast= Filled with chlorophyll and are where photosynthesis takes place in plants and other photosynthetic eukaryotes • – Thylakoids= saclike photosynthetic membranes arranged into stacks known as grana. Area where light-dependent reactions take place • – Photosystems= clusters of chlorophyll and other pigments that are organized by the thylakoids • – Stroma= Area outside the thylakoid membranes where light- independent reactions

  6. Light-dependent Reactions

  7. Figure 8-5 Chlorophyll Light Absorption Section 8-2 Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a V B G Y O R

  8. Electron Carriers • Electron Transport= The transfer of a pair of high energy electrons & their energy to another molecule • Electron Carriers= The “bucket” or carrier that moves electrons and their energy from molecule to the next • EX: NADP+: Accepts and holds a pair of high-energy electrons and an H+ ion, converting NADP+ into NADPH turning energy from the sun into chemical energy . • An analogy would be a pan carrying hot coals like the NADP+ carries two electrons and a H+ ion.

  9. ATP Formation

  10. Adenosine Triphosphate (ATP) Adenine Ribose 3 Phosphate groups

  11. ADP and ATP (Electron Carriers) ATP ADP Energy Energy Adenosine triphosphate (ATP) Adenosine diphosphate (ADP) + Phosphate Partially charged battery Fully charged battery

  12. Light-Dependent Reactions • Light-Dependent Reactions: Use energy from sunlight to produce the energy carriers ATP and NADPH and oxygen. • – Reactions occur within the thylakoid membranes of chloroplasts

  13. Light-dependent Reactionshttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20and%20ATP%20Synthesis

  14. Figure 8-10 Light-Dependent Reactions Section 8-3 Hydrogen Ion Movement Chloroplast Photosystem II ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Photosystem I ATP Formation

  15. Photosynthesis

  16. Steps in Photosynthesis • Photosynthesis: Has five major steps that occur within the thylakoid membrane of the chloroplast • – 1. Photosystem II: Light absorbed by photosystem II is used to break up water molecules into energized electrons, hydrogen ions (H+) and oxygen. • – 2. Electron Transport Chain: High-energy electrons from photosystem II move through the electron transport chain into photosystem I.

  17. Steps in Photosynthesis • – 3. Photosystem I: Electrons released by photosystem II are energized again in photosystem I. Enzymes in the membrane use these electrons to make NADPH/ • – 4. Hydrogen Ion Movement: The inside of the thylakoid membrane is charged with H+ ions. This causes the outside of the thylakoid membrane to be negatively charged and the inside of the membrane to be positively charged.

  18. Steps in Photosynthesis • – 5. ATP Formation: As hydrogen ions pass through ATP synthase, their energy is used to convert ADP into ATP. As it rotates ATP synthase (enzyme) binds ADP and P+ group to create ATP. Because of this, light-dependent transport produces high energy electron AND ATP. • SUMMARY: • Light dependent reactions use water, ADP and NADP+ to produce oxygen, ATP and NADPH (Water, ADP, NADP+ Oxygen, ATP, NADPH) • ATP and NADPH then provide energy to build energy containing sugars from low-energy compounds.

  19. Light-independent Reactions • Calvin Cycle: Energy stored in the ATP and NADPH formed during photosynthesis, is used to build high-energy sugars that can be stored for a long period of time. • – Does not require light and is called light independent reaction • – Takes place in the stroma of the chloroplasts

  20. Calvin Cyclehttp://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html

  21. Steps in the Calvin Cycle • The Calvin Cycle has four major steps: • – 1. C02 Enters the Cycle: 6 CO2 molecules are combined with six 5- carbon molecules to produce three 12-carbon molecules • – 2. Energy Input: Energy from ATP and electrons from NADPH convert the twelve 3-carbon molecules into higher-energy forms • – 3. 6-Carbon Sugar Produced: two 3-carbon molecules are removed to produce sugars, lipids, amino acids, and other compounds

  22. Steps in the Calvin Cycle • – 4. 5-Carbon Molecules Regenerated: the 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to start the next cycle : )

  23. Figure 8-11 Calvin Cycle Section 8-3 CO2 Enters the Cycle Energy Input ChloropIast 5-Carbon Molecules Regenerated 6-Carbon Sugar Produced Sugars and other compounds

  24. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Concept Map Section 8-3 Photosynthesis includes takes place in uses use take place in to produce to produce of

  25. Light CO2 Sugars O2 Figure 8-7 Photosynthesis: An Overview Section 8-3 Chloroplast Chloroplast NADP+ ADP + P Light- Dependent Reactions Calvin Cycle ATP NADPH

  26. Factors Affect Photosynthesis • Various Factors Affect the Rate of Photosynthesis. • Some of these factors are: 1. Amount of available water • – EX: Plants in dry areas have waxy leaves to prevent water loss 2. Temperature • – EX: Enzymes work best between 0° and 35°C. Temps above or below this range may slow down photosynthesis or stop it entirely 3. Light Intensity • 1. EX: The higher the intensity the higher the rate of photosynthesis. There is a maximum limit however. This varies from plant to plant

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