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Photosynthesis

Photosynthesis. Chapter 8. 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

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Photosynthesis

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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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