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Photosynthesis: Harnessing Sunlight for Energy Production

This chapter explores the process of photosynthesis and how living organisms use the energy from sunlight to produce food. It also examines the role of ATP as an energy source in cells and the absorption of light by chlorophyll.

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Photosynthesis: Harnessing Sunlight for Energy Production

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  1. CHAPTER 8: PHOTOSYNTHESIS

  2. 8-1 Energy of Life • Energy= • Living organisms depend on energy. • Living things get energy from _______. • The ultimate source of energy is the _____. Plants & other types of organisms can use light energy from the sun to produce food! The ability to do work food sun

  3. Autotrophs and Heterotrophs • Autotrophs= • Example: plants use sunlight to make food • Heterotrophs= • Example: ___________- eat plants • ___________- eat animals that • have stored energy from • plants they eat • ___________- eat decomposing • organisms Organisms that make their own food Organisms that need to consume food for energy herbivores carnivores detritovores

  4. ATP • B. Chemical Energy and ATP • Forms of energy: light, heat, electricity, and • _____ (Adenosine Triphosphate)= Section 8-1 Chemical energy (stored in bonds) ATP The basic energy source (chemical energy) of all cells Adenine Ribose 3 Phosphate groups

  5. Storing Energy • ADP (Adenosine Diphospate) contains ____ phosphates instead of 3. • If a cell has extra energy, 2. Releasing Energy • To release energy stored in ATP, 2 Small amounts can be stored by adding a phosphate group to ADP molecules to produce ATP. The cell can break the high energy bond between the 2nd and 3rd phosphate group

  6. Figure 8-3 Comparison of ADP and ATP to a Battery Section 8-1 ADP ATP Energy Energy Adenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP) Partially charged battery Fully charged battery

  7. Using Biochemical Energy • How ATP is used in the cell • - • - aids in • - • - • Cells contain a small amount of ATP. Only enough to provide a few seconds of activity. • ATP is great at ________________ but not good at • Glucose stores ___ times more energy than ATP. • The energy stored in Glucose can be used to Carry out active transport moving organelles throughout the cell Protein synthesis Producing light (ex. fireflies) transferring energy Storing large amounts of energy 90 regenerate ATP when the cell needs it.

  8. 8-2 Photosynthesis: An Overview • Photosynthesis= • Plants convert ______________ → ______________ through a series of oxidation/reduction reactions. Process where plants use energy of sunlight to convert water and carbon dioxide into high-energy Carbohydrates-sugars-starches- and oxygen, a waste product. Sunlight energy Chemical energy 6 CO2 + 6H2O + SUNLIGHT→ C6H12O6(SUGAR) + 6O2

  9. sunlight O2 C6H12O6 CO2 H2O 6 CO2 + 6H2O + SUNLIGHT → C6H12O6 (SUGAR) + 6O2

  10. REDOX REACTIONS Reduction: Gain electrons Oxidation: Lose electrons

  11. Photosynthesis: Reactants and Products Section 8-2 Light Energy Chloroplast Sugars + O2 CO2 + H2O

  12. A. Investigating Photosynthesis • Investigations into photosynthesis began with the following question: “When a tiny seedling grows into • a tall tree with a mass of several tons, • where does the tree’s increase in mass come from?”

  13. Van Helmont’s • ______________ Experiment (1643) • Put soil in pot and took mass • Took a seedling and took mass • Put seed in soil...watered...waited five years... the seedling became a tree. • He concluded that • He determined the the mass came from water the “hydrate” in the carbohydrate portion of photosynthesis

  14. ___________ Experiment (1771) • Put a lit candle in a bell jar- • Placed a mint plant in the jar with the candle- • Concluded • He determined Priestley’s The flame died out. Flame lasted longer plants release a substance needed for candle burning. plants release oxygen

  15. Jan Ingenhousz • ________________Experiment (1779) • Put aquatic plants in light... • Put aquatic plants in dark... • He determined: • _______________ (1948) • He determines • Known as the produced oxygen No oxygen Light is needed to produce oxygen Melvin Calvin carbon’s path to make glucose Calvin cycle

  16. B. Light and Pigments • Photosynthesis requires ______ (soil), ____________ (air), and ____ (sun), and ________ (a molecule in chloroplasts). • Energy from the sun is in the form of _____. • Sunlight= perceived as white light= • The wavelengths you can see are part of the _______________. • Plants capture light with light absorbing molecules called ________. • The main pigment is chlorophyll (2 kinds) water Carbon dioxide light chlorophyll light A mixture of different wavelengths Visible Spectrum pigments Chlorophyll a Chlorophyll b

  17. Gammarays Micro-waves Radio waves X-rays UV Infrared Visible light Wavelength (nm) Blue-violet • Chlorophyll absorbs light in the __________ and ___ wavelengths Figure 8-5 Chlorophyll Light Absorption red Section 8-2 Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a V B G Y O R

  18. green • Chlorophyll reflects ______ wavelengths (that’s why plants appear green) • The energy absorbed by chlorophyll is transferred to _________ (in chloroplasts) which makes photosynthesis work. electrons

  19. Chloroplast LEAF CROSS SECTION MESOPHYLL CELL • The location and structure of chloroplasts LEAF Mesophyll Intermembrane space CHLOROPLAST Outer membrane Granum Innermembrane Grana Stroma Thylakoidcompartment Stroma Thylakoid Figure 7.2

  20. 8-3The Reactions of Photosynthesis • A. Inside a Chloroplast • Site of Photosynthesis= The chloroplasts Reflectedlight Light Chloroplast Absorbedlight Transmittedlight

  21. The Reactions of Photosynthesis 8-3 • Inside a Chloroplast • The organelle where photosynthesis takes place • Thylakoid • Saclike photosynthetic membranes • Grana (Granum) • Stacks of thylakoids • Photosystems • Clusters of pigment and protein that absorb light energy • Stroma • Area outside of the thylakoid in the chloroplast

  22. Light CO2 Sugars O2 • Photosynthesis is a two part process: • -aka: • 2. • -aka: • -aka: • -aka: Light-dependent reactions (located in thylakoid membranes) Light Reaction Light-independent reactions (located in stroma) Dark reaction Figure 8-7 Photosynthesis: An Overview Calvin Cycle Carbon fixation H20 Chloroplast Chloroplast NADP+ ADP + P Light- Dependent Reactions Calvin Cycle ATP NADPH

  23. H2O CO2 Chloroplast • An overview of photosynthesis Light NADP+ ADP+ P LIGHTREACTIONS(in grana) CALVINCYCLE(in stroma) ATP Electrons NADPH O2 Sugar Figure 7.5

  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. B. Electron Carriers • Sunlight energy is transferred to • The electrons • High energy electrons require • ANALOGY: If you wanted to transfer hot coals from one campfire to another, it requires a special carrier like a pan or bucket. • Electron carriers pass electrons from carrier to carrier to carrier; • A Key electron carrier in photosynthesis is NADP+. • NADP+ + + →→ • (electron carrier) (high energy electrons) (hydrogen ions) (energy storing compound) • When energy is needed to do cellular work, the electrons in chlorophyll. gain a lot of energy. a special carrier (molecule/compound). Forming an electron transport chain. 2e- NADPH H+ Covalent bonds of NADPH are broken to release the high energy electrons.

  26. Light-Dependent Reactions (Requires Light)·   Located in the ___________________________·   In the light reaction, ___________ is used to produce _____ and _______ thylakoid membrane light energy ATP NADPH

  27. Overview of the Light Reaction e~ e~ Electron Transport Chain Electron Transport Chain e~ e~ e~ ADP ATP e~ NADP+ NADPH light light PSII PSI 2H2O O2 + 4H+ 4e~

  28. NADP+ • Chloroplasts trap energy from the sun • Two electrons and a hydrogen molecule make NADPH • NADPH can move to other parts of the cell and make things like glucose Light-Dependent Reactions • Produce oxygen gas and convert ADP and NADP+into the energy carriers ATP and NADPH

  29. Photosystem II pigments absorbs light • Light absorbance excites electrons to a higher energy level • High-energy electrons move to the electron transport chain • Thylakoid replaces lost electrons from stored water • Two hydrogen molecules (New Electrons) • One oxygen (Waste)

  30. High-energy electrons move from photosystem II to photosystem I • Energy from the electrons is used to move hydrogen ions from the stroma to the inner thylakoid space

  31. Photosystem I uses light to reenergize the electrons • NADP+ picks up the high-energy electrons and hydrogen ions to make NADPH • Hydrogen ions are pumped across the thylakoid membrane • This results in energy that can be used to make ATP –the useable form of energy for the plant cell!

  32. The Reactions of Photosynthesis 8-3 • Hydrogen ions cannot pass through the thylakoid membrane directly • ATP synthase – membrane protein • Allows hydrogen to pass through • ATP synthase will bind ADP and phosphate  ATP • So far in light reaction: • Water breaks down - hydrogen ions and oxygen • NADP+ becomes NADPH – electrons and hydrogen ions to photosystem I • ADP to ATP via ATP synthase • YEAH!!! We have ATP, now what?

  33. KEY PLAYERS IN LIGHT REACTION: • ·Photosystem I and II: • ·Electron carriers: • ·Water: • ATP Synthase: Clusters of chlorophyll pigment ADP and NADP+ Donates electrons Enzyme (protein) that makes ATP

  34. Light Reaction Process: Hydrogen Ion Movement Chloroplast Photosystem II ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Photosystem I ATP Formation

  35. A. Photosystem II (PSII) * Absorbs light to 2H2O e- =  O2 =  H+ = B. Electron Transport Chain* The light energy * The electrons get passed split (break up) water molecules → 4H+ + 4e- + O2 Donated to chlorophyll Released into air providing oxygen for us Released inside the thylakoid membrane excites electrons increasing their energy level. down an electron transport chain to photosystem I (PSI)

  36. C. Photosystem I·        Light energy energizes electrons.·        NADP+ accepts the electrons and an H+ and are used to make _________.D. Hydrogen Ion Movement·        When water splits, ·        The difference in charges E. ATP Formation·        _____ do not cross the membrane directly. It needs the help of a membrane protein.·        H+ ions pass through the protein: NADPH H+ ions fill up the inner thylakoid membrane (making it positively charged). As a result, the stroma is negatively charged. Provides the energy to make ATP. Ions ATP synthase is an enzyme that converts ADP to ATP

  37. PRODUCTS OF THE LIGHT REACTION:·____ : Released in the air·  ______________: These contain abundant chemical energy but they are unstable. So, they are used to power the dark reaction to _________________ which can store the energy for longer periods of time. O2 ATP & NADPH help build glucose

  38. The Reactions of Photosynthesis 8-3 • Calvin Cycle • Uses ATP and NADPH from the light dependent reactions to produce high-energy sugars • Does NOT require light to proceed – it uses the energy captured from the light reactions. • This is where carbon dioxide (CO2) is used.

  39. Section 8-3 D. The Calvin Cycle (dark reaction; light independent) * Occurs in the Figure 8-11 Calvin Cycle Stroma with or without light. CO2 Enters the Cycle Energy Input ChloropIast 5-Carbon Molecules Regenerated 6-Carbon Sugar Produced Sugars and other compounds

  40. DARK REACTION PROCESS: • A. CO2 enters the system •  product= • B. Energy input • The _________________________________ are used to • C. 6-Carbon Sugar is produced • ___ of the 12 3-C are used to make glucose and • other compounds. • D. 5-Carbon Molecules Regenerated • ___ remaining 3-C are converted into 6 5-C molecules 6 CO2 combines with 6 5-C compounds 12 3-C compounds ATP & NADPH (from the light reaction) convert the 12 3-C compounds into a higher energy form. 2 10

  41. Summary

  42. The Reactions of Photosynthesis 8-3 • Factors affecting photosynthesis • H2O • Plants require water for photosynthesis to occur • Dry conditions - waxy covering • Temperature • Enzymes require temperature range of 0o – 35o C • Light Intensity • The more light the more photosynthesis to a point

  43. PRODUCTS OF THE CALVIN CYCLE (DARK REACTION):*E. Factors Affecting Photosynthesis**   Plants often have a ______ coating to protect against ** The greater the _____________, the better photosynthesis functions (up to a point). High Energy Sugars Shortage of water can stop/slow down photosynthesis waxy Very low/high temperatures (damages enzymes) can stop/slow down photosynthesis (optimal temp.= 0°– 35° C Light intensity

  44. California State Standards • Cell Biology 1a: usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide

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