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Introduction to Photosynthesis

Introduction to Photosynthesis. AP Biology Mrs. Hansell. Ways to Acquire Energy. Autotroph - self-feeders- make own food Plants, some bacteria Photoautotroph- organisms that use light as a source of energy to make food Heterotroph - unable to make own food, consume others Animals.

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Introduction to Photosynthesis

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  1. Introduction to Photosynthesis AP Biology Mrs. Hansell

  2. Ways to Acquire Energy • Autotroph- self-feeders- make own food • Plants, some bacteria • Photoautotroph- organisms that use light as a source of energy to make food • Heterotroph- unable to make own food, consume others • Animals

  3. Parts of a Leaf

  4. Chloroplast

  5. The Nature of Sunlight • Form of energy known as electromagnetic energy • Travels in waves • Wavelength- distance between crests in the waves • Electromagneticspectrum- entire range of radiation

  6. Electromagnetic Spectrum

  7. Visible Light • Segment most important to life – detected as various colors by the human eye • Photons- energy particles that make up light • Shorter the wavelength- more energy in photon • Violet light has more energy than red light

  8. Photosynthetic Pigments • Light meets matter- reflected, transmitted, absorbed • Pigment- absorb visible light • Colors we see are wavelengths that are reflected • Plants appear green- reflect green light absorbs violet-blue and red • Spectrophotometer- instrument that measures the ability of a pigment to absorb various wavelengths of light

  9. Spectrophotometer

  10. Photosynthetic Pigments • AbsorptionSpectrum- a graph plotting a pigments light absorption versus wavelength

  11. Absorption Spectra of Chloroplast • Chlorophylla absorbs violet-blue and red light—best for photosynthesis • Blue-Green is reflected—less effective • Actionspectrum- profiles the effectiveness of different wavelengths

  12. Accessory Pigments • Broaden spectrum of colors absorbed • Chlorophyllb- reflects yellow-green • Carotenoids- hydrocarbons various shades of yellow and orange (absorb violet and blue-green light) • Photoprotection- dissipate excessive light energy that could damage chlorophyll or interact with O2

  13. Excitation of Chlorophyll • What happens when chlorophyll and other pigments absorb light? • Molecule absorbs photon of light—electron in molecule excited to orbital with more potential energy • Groundstate- electron in normal orbital • Excitedstate- absorb photon—gain energy

  14. Excitation of Chlorophyll • Ground state to excited state does not last long • Excess energy released as heat when electron goes from excited back to ground state • Makes top of automobiles hot on sunny day—white cars cooler—reflect all visible light • Some pigments emit light and heat as electron falls to ground state--Fluoresce

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