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By the end of this lecture you will be able to:

LEARNING OBJECTIVES. By the end of this lecture you will be able to: Understand that ENERGY can be transformed from one form to another. Know that energy exist in two forms; free energy - available for doing work or as heat - a form unavailable for doing work.

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By the end of this lecture you will be able to:

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  1. LEARNING OBJECTIVES • By the end of this lecture you will be able to: • Understand that ENERGY can be transformed from one form to another. • Know that energy exist in two forms; free energy - available for doing work or as heat - a form unavailable for doing work. • Appreciate that the Sun provides most of the energy needed for life on Earth. • Explain why photosynthesis is so important to energy and material flow for life on earth. • Know why plants tend to be green in appearance. • Equate the organelle of photosynthesis in eukaryotes with the chloroplast. • Describe the organization of the chloroplast. • Understand that photosynthesis is a two fold process composed of the light-dependent reactions (i.e., light reactions) and the light independent reactions (i.e. Calvin Cycle or Dark Reactions). • Tell where the light reactions and the CO2 fixation reactions occur in the chloroplast. • Define chlorophylls giving their basic composition and structure. • Draw the absorption spectrum of chlorophyll and compare it to the action spectrum of photosynthesis. • Define the Reaction Centers and Antennae and describe how it operates. • Describe cyclic photophosphorylation of photosynthesis. • Describe noncyclic photophosphorylation of photosynthesis.

  2. THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

  3. THE BASICS OF PHOTOSYNTHESIS • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists • Autotrophs generate their own organic matter through photosynthesis (c) Euglena (d) Cyanobacteria (b) Kelp (a) Mosses, ferns, and flowering plants

  4. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

  5. Food Chain

  6. THE FOOD WEB

  7. WHY ARE PLANTS GREEN? It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that… Kermit the Frog

  8. Electromagnetic Spectrum and Visible Light Gammarays Infrared & Microwaves X-rays UV Radio waves Visible light Wavelength (nm)

  9. WHY ARE PLANTS GREEN? Different wavelengths of visible light are seen by the human eye as different colors. Gammarays Micro-waves Radio waves X-rays UV Infrared Visible light Wavelength (nm)

  10. The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others. Reflected light Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.

  11. Why are plants green? Reflected light Transmitted light

  12. WHY ARE PLANTS GREEN? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

  13. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED • Chloroplasts absorb light energy and convert it to chemical energy Reflected light Light Absorbed light Transmitted light Chloroplast

  14. AN OVERVIEW OF PHOTOSYNTHESIS • Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbondioxide Water Glucose Oxygengas PHOTOSYNTHESIS

  15. AN OVERVIEW OF PHOTOSYNTHESIS Light • The light reactions convert solar energy to chemical energy • Produce ATP & NADPH Chloroplast NADP ADP + P Calvin cycle • The Calvin cycle makes sugar from carbon dioxide Light reactions

  16. Chloroplasts: Sites of Photosynthesis • Photosynthesis • Occurs in chloroplasts, • All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts • The green color comes from chlorophyll in the chloroplasts • The pigments absorb light energy

  17. Photosynthesis occurs in chloroplasts • In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts • A chloroplast contains: • stroma, a fluid • grana, stacks of thylakoids • The thylakoids contain chlorophyll • Chlorophyll is the green pigment that captures light for photosynthesis

  18. 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

  19. Chloroplast Pigments • Chloroplasts contain several pigments • Chlorophyll a • Chlorophyll b • Carotenoids Figure 7.7

  20. Different pigments absorb light differently

  21. Chloroplast • A Photosynthesis Road Map Light Stroma NADP Stack of thylakoids ADP + P Light reactions Calvin cycle Sugar used for  Cellular respiration  Cellulose  Starch  Other organic compounds

  22. Review: Photosynthesis uses light energy to make food molecules • A summary of the chemical processes of photosynthesis Chloroplast Light Photosystem IIElectron transport chains Photosystem I CALVIN CYCLE Stroma Electrons Cellular respiration Cellulose Starch Other organic compounds LIGHT REACTIONS CALVIN CYCLE

  23. It's not that easy bein' green… but it is essential for life on earth!

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