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Lesson Overview

Lesson Overview. 8.2 Photosynthesis : An Overview. Light. Energy from the sun travels to Earth in the form of light. Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum. Pigments.

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Lesson Overview

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  1. Lesson Overview 8.2 Photosynthesis: An Overview

  2. Light • Energy from the sun travels to Earth in the form of light. • Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum.

  3. Pigments • Plants gather the sun’s energy with light-absorbing molecules called pigments. • The plants’ principal pigment is chlorophyll.

  4. Pigments

  5. Chloroplasts • Chloroplasts contain saclike photosynthetic membranes called thylakoids, which are interconnected and arranged in stacks known as grana. • The fluid portion outside of the thylakoids is known as the stroma.

  6. Energy Collection • When chlorophyll absorbs light, a large fraction of the light energy is transferred to electrons. These high-energy electrons make photosynthesis work.

  7. High-Energy Electrons • The high-energy electrons produced by chlorophyll are highly reactive and require a special “carrier.” • Think of a high-energy electron as being similar to a hot potato. If you wanted to move the potato from one place to another, you would use an oven mitt —a carrier—to transport it. • Plants use electron carriers to transport high-energy electrons from chlorophyll to other molecules.

  8. High-Energy Electrons • NADP+(nicotinamide adenine dinucleotide phosphate) is a carrier molecule. • NADP+ accepts and holds two high-energy electrons, along with a hydrogen ion (H+). In this way, it is converted into NADPH. • The NADPH can then carry the high-energy electrons to chemical reactions elsewhere in the cell.

  9. An Overview of Photosynthesis • Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen. • In symbols: • 6 CO2 + 6 H2O  C6H12O6 + 6 O2 • In words: • Carbon dioxide + Water  Sugars + Oxygen

  10. An Overview of Photosynthesis • Plants use the sugars generated by photosynthesis to produce complex carbohydrates such as starches, and to provide energy for the synthesis of other compounds, including proteins and lipids.

  11. Light-Dependent Reactions • Photosynthesis involves two sets of reactions. • The first set of reactions is known as the light-dependent reactions because they require the direct involvement of light and light-absorbing pigments.

  12. Light-Dependent Reactions • The light-dependent reactions use energy from sunlight to produce ATP and NADPH. • These reactions take place within the thylakoid membranes of the chloroplast. • Water is required as a source of electrons and hydrogen ions. Oxygen is released as a byproduct.

  13. Light-Independent Reactions • During light-independent reactions, ATP and NADPH molecules produced in the light-dependent reactions are used to produce high-energy sugars from carbon dioxide. • No light is required to power the light-independent reactions. • The light-independent reactions take place outside the thylakoids, in the stroma.

  14. Questions • In the process of photosynthesis, plants convert the energy of sunlight into chemical energy stored in the bonds of _________. • Carbohydrates • Photosynthetic organisms capture energy from sunlight with ________. • Pigment • The plant’s principal pigment is _______. • Chlorophyll • Photosynthesis takes place in ___________. • Chloroplasts • T or F - Chloroplasts contain an abundance of saclike photosynthetic membranes called thylakoids. • TRUE • T or F - The fluid portion of the chloroplast, outside of the thylakoids, is known as the matirx. • FALSE - STROMA • Raising the energy levels of electrons on the chlorophyll molecule, light energy can produce a steady supply of _______________electrons, which is what makes photosynthesis work. • High Energy

  15. Questions • 8. An electron _________is a compound that can accept a pair of high-energy electrons and transfer them, along with most of their energy, to another molecule. • Carrier • 9. NADP+ is converted to ______________as it accepts and transfers electrons to chemical reactions elsewhere in the cell. • NADPH • 10. What is the overall equation of photosynthesis? • 6CO2 + 6H2O + light  C6H12O6 + 6O2 • 11. The light- ______________reactions produce ATP and NADPH from sunlight in the thylakoid membranes. • Dependent • 12. The light-______________t reaction in the stroma, sugars are created from carbon dioxide using the ATP and NAPH from the light-dependent reactions. • Independent

  16. Photosynthesis REVIEW

  17. Photosynthesis REVIEW

  18. Photosynthesis REVIEW

  19. Journal • What is the equation for photosynthesis?

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