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Photosynthesis

Photosynthesis. Energy & Life. Photosynthesis is the process of capturing and transforming the energy of sunlight into chemical energy. (What type of organisms can make their own food?) a. Autotrophs – organisms that can make their own food

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Photosynthesis

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  1. Photosynthesis

  2. Energy & Life Photosynthesis is the process of capturing and transforming the energy of sunlight into chemical energy. (What type of organisms can make their own food?) a. Autotrophs – organisms that can make their own food b. Heterotrophs – organisms that obtain energy from the food they consume

  3. Chemical Energy and ATP a. ATP – energy molecule used by cells (Fig. 8-2) b. Energy is stored in the bonds between phosphate c. When these bonds are broken energy is released Energy & Life

  4. Energy & Life

  5. Using Biochemical Energy a. Active Transport http://www.dnatube.com/video/359/Active-Transport b. Motor proteins move organelles throughout the cell http://www.youtube.com/watch?v=tL99pwdvmhU c. Synthesize various molecules Energy & Life

  6. Understand the significance of Helmont’s, Priestley’s, and Ingenhousz’s experiments. 6CO2 + 6H2 O  C6H12O6 + O2 Photosynthesis: An Overview

  7. Light and Pigments (Fig. 8-5) • A. Wavelength – distance between crests; shorter wavelengths have higher energy than longer wavelengths Photosynthesis: An Overview

  8. Light and Pigments (Fig. 8-5) • B. Photon – a particle of light • C. In photosynthetic organisms, absorbed energy is used to make chemical energy (glucose) • D. Photosynthetic pigment – molecule that absorbs light (color you see is the color being reflected) • 1. chlorophyll a - primary pigment; converts light energy to chemical • energy Photosynthesis: An Overview

  9. Light and Pigments (Fig. 8-5) • D. Photosynthetic pigment (con’t) • 1. chlorophyll a - (con’t) • a. reflects green light • b. absorbs red & blue light • c. normally hides other • pigments • 2. Chlorophyll b – accessory • pigment; absorbs light and • transfers the energy to • chlorophyll a Photosynthesis: An Overview

  10. Light and Pigments (Fig. 8-5) • D. Photosynthetic pigment (con’t) • 3. carotenes & xanthophylls – • accessory pigment; colors • can be seen in autumn when • chlorophylls start to break • down • E. Absorption spectrum – the different • colors (wavelengths) of light • absorbed by each pigment Photosynthesis: An Overview

  11. Inside a chloroplast – organelle in • which photosynthesis occurs Reactions of Photosynthesis

  12. Inside a chloroplast • A. Thylakoids – flattened sacs of photosynthetic membranes; pigments and proteins are organized into photosystems in order for light energy to be captured & stored as chemical energy • B. grana – stacks of thylakoids • C. stroma – region between grana Reactions of Photosynthesis

  13. II. Electron Carriers – molecules that can accept a pair of high-energy electrons and protons and transfer them to another molecule (NADP+) Reactions of Photosynthesis

  14. There are two sets of reactions that take place within the chloroplasts: The light dependent reactions & the Calvin Cycle (also know as the light independent or the dark cycle) Reactions of Photosynthesis

  15. Light Dependent Reactions • A. Takes place only in the presence of light • B. Occurs on membranes of thylakoids • C. Produces high energy compounds that are used in the dark reaction: ATP and NADPH • D. Photosystem II • 1. pigments absorb light energy and electrons are boosted to a higher energy level Reactions of Photosynthesis

  16. Light Dependent Reactions • D. Photosystem II (con’t) • 2. lost electrons are replaced by the splitting of H2O into 2 e-,2 p+, and O2 • a. electrons are picked up by NADP • b. protons (H+) are pumped into inner thylakoid space Reactions of Photosynthesis

  17. Light Dependent Reactions • E. Photosystem I • 1. pigments use energy from light to re- energize the elctrons from photosystem II • 2. produces NADPH which also powers the Calvin Cycle Reactions of Photosynthesis

  18. Light Dependent Reactions • http://www.youtube.com/watch?v=Oi2_n2wbB9o Reactions of Photosynthesis

  19. The Calvin Cycle – (light independent, dark reaction) – uses ATP and NADPH from the light dependent reactions to produce high energy sugars (Fig. 8-11) • A. Takes place with or without the presence of light as long as ATP and NADPH are available • B. Occurs in the stroma of chloroplast • C. 6CO2 molecules enter the cycle from the atmosphere and combine with 6 five carbon molecules Reactions of Photosynthesis

  20. The Calvin Cycle (con’t) • D. The resulting 12 three carbon molecules use the energy from ATP and NADPH to produce 12 high energy three carbon molecules • E. 2 of these molecules are used to synthesize sugar and other compounds • F. The remaining 10 molecules are used to produce more of the “starting” 6 carbon molecule of the cycle Reactions of Photosynthesis

  21. The Calvin Cyclehttp://www.youtube.com/watch?v=_NIhg1qa_L0

  22. FactorsAffectingPhotosynthesis • A. Light intensity – as intensityincreases the rate of photosynthesisincreases (up to a point) • B. Temperature – photosynthesisoccursrapidlyatspecifictemp.; extreme temps. are damaging to enzymes • C. H2O – decrease in water slows rate of photosynthesis • D. Minerals – must bepresent in certain amounts Reactions of Photosynthesis

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