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THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH THE BASICS OF PHOTOSYNTHESIS • All plants are photosynthetic autotrophs, as are some bacteria and some protists – These autotrophs generate their own organic matter through photosynthesis – Sunlight energy is transformed to energy stored in the form of chemical bonds (c) Euglena (b) Kelp (a) Mosses, ferns, and flowering plants (d) Cyanobacteria Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Food Chain THE FOOD WEB 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 Carbon dioxide Water Glucose PHOTOSYNTHESIS Oxygen gas PHOTOSYNTHESIS Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids). • The location and structure of chloroplasts Chloroplast LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll Stomata CHLOROPLAST Intermembrane space Outer membrane Granum Grana Stroma Inner membrane Stroma Thylakoid Thylakoid compartment Chloroplasts: Sites of Photosynthesis • Photosynthesis – Occurs in chloroplasts - organelles – All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts, therefore is the site of most photosynthesis • The green color comes from chlorophyll (pigment) in the chloroplasts (organelle) • The pigments purpose is to absorb light energy Photosynthesis occurs in 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 Draw and Label the parts of the Chloroplast! THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED • Chloroplasts absorb light energy and convert it to chemical energy Light Reflected light Transmitted light Chloroplast Absorbed light 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 Electromagnetic Spectrum and Visible Light Gamma rays X-rays UV Infrared & Microwaves Visible light Wavelength (nm) Radio waves WHY ARE PLANTS GREEN? Different wavelengths of visible light are seen by the human eye as different colors. Gamma rays X-rays UV Infrared Visible light Wavelength (nm) Microwaves Radio waves The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others. Sunlight minus absorbed wavelengths or colors equals the apparent color of an object. Why are plants green? Chloroplast Pigments • Chloroplasts contain several pigments – Chlorophyll a – Chlorophyll b – Carotenoids Figure 7.7 Different pigments absorb light differently It's not that easy bein' green… but it is essential for life on earth!
