Lecture_12_DulaiS09_Photosynthesis

Lecture_12_DulaiS09_Photosynthesis - Photosythesis...

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Photosythesis Photosythesis Bio1 Spring 2009 Lecture 12
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Look at the bigger picture: All living things need 1) Carbon & 2) Energy Troph = refers to an organism’s source of carbon and energy Heterotrophs not self-nourishing get carbon and energy by eating others so dependent ultimately upon autotrophs Autotrophs Auto = self so autotrophs are self-nourishing get their carbon from carbon dioxide in air – through leaves dissolved in water – through roots
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AUTOPROPH Subdivisions PHOTOautotroph PHOTOautotroph – energy source is light (=photo) Photoautotrophy is a property of organisms in the Domains… - Eubacteria (ex. cyanobacteria), and - Eukarya ( green algae including land plants & many unicellular eukaryotes) Photoautotrophs perform photosynthesis to make sugars and other macromolecules cyanobacteria unicellular diatom algae Fucus unicellular Euglena
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Note: Note: The vast majority of the organic carbon found on Earth is The vast majority of the organic carbon found on Earth is due to the process of photosynthesis due to the process of photosynthesis Generalized equation summarizing photosynthesis Where does the light energy originate? Where does the light energy originate? Plants transform energy from Plants transform energy from photons of photons of light light to to rearrange the bonds in carbon dioxide and water rearrange the bonds in carbon dioxide and water
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But First… Understanding Light
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What is sent by the Sun? What does the electromagnetic spectrum include? · All energy from the Sun = electromagnetic spectrum · entire range of energy dispersing from sun, described in terms of wavelength = energy content · energy content decreases with increasing wavelength energy content decreases with increasing wavelength
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How do humans experience the visible portion of the electromagnetic spectrum? •Answer: As colors (and white light) we can see with our eyes. • Conclusion: Living systems are places where energy is concentrated. What must living systems do to exist and persist when energy has the tendency to spontaneously disperse? · Have mechanism for concentrating energy. · Sunlight composed of all the wavelengths (colors) of the visible spectrum!! Highest energy Lowest energy visible light
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What makes objects appear the color they do? Three things can occur when light (radiation) hits matter · 1. some of it can be absorbed Of these three outcomes, which makes light available for our eyes to detect? · 2. some can be transmitted · 3. some can be reflected · the color corresponding to wavelengths of light arriving at our eyes · only reflected or transmitted light can reach our eyes (the retina) What color does an object appear to us? · yellow objects illuminated by white light appear yellow because all other colors (wavelengths) are absorbed and yellow is reflected to eyes
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Why do plant leaves appear green when Why do plant leaves appear green when illuminated by sunlight?
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Lecture_12_DulaiS09_Photosynthesis - Photosythesis...

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