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MU BIO 116 - Part One of Photosynthesis- Photochemistry

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Biol 116 1st Edition Lecture 9 Outline of Last Lecture I. Laws of Thermodynamics II. EnergyIII. Free EnergyIV. Enzymesa. Inhibition (2 types)Outline of Current Lecture I. Trophic Organization a. Types of Phototrophs II. Photosynthesisa. ChloroplastsIII. Photochemistrya. Part 1 of Photochemistryb. Part 2 of Photochemistryc. Transfer of electrons from PSII to PSI Current LecturePart 1: Photochemistry *Today’s lecture only focuses on the first half of photosynthesis- photochemistryTrophic Organization Heterotroph- must eat other organisms Autotroph- convert inorganic molecules into organic molecules Chemotrophic- chemicals into energyPhototrophic- light into energy These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Types of Phototrophs -Eukaryotes green plants - oxygenicalgae- oxygenicPhotosynthesis: a process by which light energy is captured and the energy is used to synthesizecarbohydrates from CO2 and H2O releasing O2 in the processCO2 + H2O + light => sugar + O2The process is divided into two parts1) Capture of light energy= photochemistry 2) Synthesis of sugars = biochemistry CO2 + H2O + light => 3 carbon sugar + O2within photosynthesis, a three carbon sugar is produced it is important to note that glucose and sucrose are synthesized afterwards in a separate reaction Chloroplasts: structures within plants and algae where photosynthesis occurs Chloroplast Structure: -have an outer and inner membrane (double lipid bilayer)-inside the chloroplast are the thylakoids: embedded in an aqueous medium called the stroma, mostly hollow, inside of thylakoid called the lumen Photochemistry-during this process O2 (molecular oxygen) diffuses out once H2O is broken Light Energy-part of electromagnetic radiation spectrum-light: energy pockets called photons Part of the wavelengths that cause photosynthesis: the photosynthetically active radiation (aka visible part of the light spectrum) -short, left hand side of spectrum = very energetic-long, right hand side of spectrum = less energetic PAR (photosynthetically active radiation) is generally from about 400 nm to 700 nm in wavelengthPart 1 of PhotochemistryPigments: molecules with the capability to absorb photons , found in the thylakoid membrane Chlorophyll A and B (nearly the same except for small change on ring at the top-has a ring (called a porphyrin) embedded in the thylakoid membrame -has a hydrophilic tail -when the photon hits the ring the electrons in that region undergo excitation to a higher energy level (takes about 1 billionth of a second)-when it goes up it takes in energy and when it comes back down it emits energy-the energy that is emitted can go 3 different ways-lost as heat-lost as light (fluorescence)-can be conserved and used to drive photochemistry Part 2 of PhotochemistryPhotosystem: pigment (made of protein) complex which absorbs light and uses the absorbed light energy to drive energy and electron transfer Photosystem II => maximally at 680 nm Photosystem I => maximally at 700 nmTransfer of electrons from PSII to PSI Photon from sun is absorbed => absorbed by pigment in photosystem II => goes to photosystemI needs 2 photons to go from PSII to PSI which is what makes NADPH -The energy of an electron coming down goes to another pigment (many times) -Once it hits the reaction center the electron gets ejected and then goes to PSI to repeat the same process -PSII reaction occurs on the lumen side-it causes the splitting of H and O in H2OChemically:-First the electron is transferred using Plastoquinone -Then the electron is transferred through the cytochrome b6f (very stable) by Plastocyanin -Finally reaches the


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MU BIO 116 - Part One of Photosynthesis- Photochemistry

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