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Lecture 6

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Department
Biology
Course
Biology 1002B
Professor
Tom Haffie
Semester
Winter

Description
Biology 1002B Lecture 6 Energy Transformation 1 - Energy is captured and put into biosphere through photosynthesis - Measure of chlorophyll concentration is equal to number of photosynthetic organisms. - 50% terrestrial 50% aquatic photosynthesis. - Temp has little to do with oceanic photosynthesis - Carbon dioxide converted to glucose for photosynthesis. - This is possible because they use energy from light to drive reduction of CO2 - Reason they use glucose because it has a lot of free energy. - No energy in CO2, can’t get anything out of CO2, no electrons you can get. Oxygen is holding on to them too tight. - C-H bonds are what we need, lots of energy in the molecule, lots of free electron that can be easily removed. - Endergonic process, free energy of products is greater than reactants. Anabolic pathways, overall positive change in free energy. - Water gets oxidized to oxygen. Carbon dioxide gets reduced to glucose. - Photosynthesis can be divided into two parts: ~ Light reactions: producing ATP energy and reducing power in the form of NADPH. NADPH gives up electrons. ~ Calvin cycle: CO2 converted to carbohydrate glucose. Chloroplast Structure: - Highly conserved - Outer and inner membrane - Stroma: aqueous compartment filed with enzymes - Interior membrane organization: thylakoid membrane - Calvin cycle takes place in stroma - Thylakoid is where light reactions take place. - In thylakoid: thylakoid lumen - There is noting uniquely eukaryotic about photosynthesis. - Happened well before eukaryotes formed. Photosynthetic Electron Transport: - In thylakoid membrane - Large supra complexes (protein complexes) - Many proteins come together to make photosystem 1 and 2 and cytochrome complex. - Both PS2 and PS1 have a reaction center surrounded by antenna, chlorophyll molecules in antenna and light gets funneled to reaction entre. The reaction center chlorophyll of PS2 is P680 and of PS1 Is P700. - Photosystem 1 and 2 absorb a photon of light, light is funneled to reaction centers, chlorophylls get oxidized (photochemical event) electron from P680 leaves and travels down electron transport chain to PS1. - Big pool of PQ molecules in membrane to shovel electrons. - PQ would fall apart if too fluid, too rigid, PQ would have trouble travelling rapidly. - P680 is oxidized, gets electron from splitting of water. - When PQ picks up electron from PS2 it becomes negatively charged, hard time to go through membrane, then picks up proton from stroma now neutrally charged. - Proton gets dropped in thylakoid membrane. - pH of lumen becomes very low compared to that of stroma. - Electrochemical gradient created. Can do work with this gradient. Can harvest gradient to do work. Chemiosmosis is how we harvest an electrochemical gradient to do work. - Only way for protons to get back across, must move through ATP synthase (protein
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