BIMM 120 Lecture12_ReadingGuide.051011

BIMM 120 Lecture12_ReadingGuide.051011 - Lecture 12...

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Lecture 12 – BIMM120.SP11 LECTURE 12 – May 10, 2011 (BLACK = this lecture / BLUE = different lecture / RED = not covered in lecture ) Chapter 20 – Metabolic Diversity: Phototrophy, Autotrophy, Chemolithotrophy, and Nitrogen Fixation (pp.578-595; 596-602; 605-608) I. The Phototrophic Way of Life 20.1 Photosynthesis Photosynthesis o Photosynthesis is the conversion of light energy to chemical energy o Organisms that carry out photosynthesis are called phototrophs o Most phototrophs are also autotrophs, capable of growing with CO 2 as the only carbon source o Photoautotrophy is when energy from light is used in the reduction of CO 2 to organic compounds o Photoheterotrophy is when autotrophs use organic carbon as their carbon source o Photosynthesis requires light-sensitive pigments (the chlorophylls) Energy Production and CO 2 Assimilation o For autotrophic growth, energy is supplied from ATP, whereas electrons for the reduction of CO 2 come from NADH (or NADPH) o In oxygenic photosynthesis , oxygen is produced o In anoxygenic photosynthesis , oxygen is not produced 20.2 Chlorophylls and Bacteriochlorophylls Chlorophylls and Bacteriochlorophylls o Photosynthesis occurs only in organisms that produce some form of chlorophyll (oxygenic phototrophs) or bacteriochlorophyll (anoxygenic phototrophs) Chlorophyll Diversity o There are a number of different chlorophylls and bacteriochlorophylls and they are distinguished by their unique absorption spectrums o By having different pigments, different organisms can coexist in an illuminated habitat, each using wavelengths of light Photosynthetic Membranes and Chloroplasts o The chlorophyll pigments and all the other components of the light-gathering apparatus are present within special membrane systems, the photosynthetic membranes o In eukaryotes, photosynthesis is associated with intracellular organelles, the chloroplasts o In prokaryotes, chloroplasts are absent. Here photosynthetic pigments are integrated into internal membrane systems Reaction Centers and Antenna Pigments 1
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Lecture 12 – BIMM120.SP11 o Reaction centers are a small number of pigment molecules that participate directly in the conversion of light energy to ATP o Antenna pigments function to harvest light and funnel the energy to the reaction center Chlorosomes o Chlorosomes are giant antenna systems   found in green sulfur bacteria, such as Chlorobium and Chloroflexus 20.3 Carotenoids and Phycobilins Carotenoids o Carotenoids are hydrophobic light-sensitive pigments that are firmly embedded in the membrane o Carotenoids are closely associated with chlorophyll or bacteriochlorophyll but do not function directly in ATP synthesis. However, they can transfer energy to the reaction center o Carotenoids function primarily as photoprotective agents Phycobiliproteins and Phycobilisomes o Phycobiliproteins are the main antenna pigments of cyanobacteria and red
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BIMM 120 Lecture12_ReadingGuide.051011 - Lecture 12...

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