THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

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

2. THE BASICS OF PHOTOSYNTHESIS • Plants are photosynthetic autotrophs, as are some bacteria and protists • Autotrophs generate their own organic matter through photosynthesis • Sunlight energy is transformed to energy stored in the form of chemical bonds (c) Euglena (d) Cyanobacteria (b) Kelp (a) Mosses, ferns, and flowering plants

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

4. Food Chain

5. THE FOOD WEB

6. 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

7. PHOTOSYNTHESIS Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

8. 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

9. Chloroplasts: Sites of Photosynthesis • Photosynthesis • Occurs in chloroplasts, organelles in certain plants • 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

10. 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

11. 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

12. 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

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

14. 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)

15. 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.

16. Why are plants green? Reflected light

17. 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 • ATP generated by the light reactions provides the energy for sugar synthesis • The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose Light reactions

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

19. Different pigments absorb light differently

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