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Bio First Midterm Notes

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Biology 1002B
Tom Haffie

Bio 1200b First Exam Review Will Burke Lecture 1Chlamydomonas How does light interact with biology Two major waysA source of ENERGY and a source of INFORMATION Chlamydomonas is a perfect example Chlamy contains an eyespot within its chloroplast It is used to enable the cell to orientate itself with light so it can harvest lots of it It will swim towards the light source to maximize photosynthesisChlamydomonas are very popular in labs and can grow in all different conditions from warm to the Antarctic These are called extremophiles They would die under standard conditionsAlmost all eukaryotic cells are much larger than a bacterium Chlamy has a thousand times larger volume than EColi Complexity can be defined as genome size though this is inaccurate in many cases as similar organisms have drastically different genome sizes It is not so much about genome size but PROTEIN CODING GENOMES Phototaxis Movement towards light Chlamy also runs away from light when there is too much light Too much light the cells damage when they harvest too much because it produces reactive oxygen that kills the cellThe eyespot and the eye appear to be homologiesLecture 2Light Light behaves like a wave The shorter the wave length gamma rays the higher the intensity Light can also be seen as small packets photons The amount of energy can be compared energy in red light vs green light The energy in a blue photon is the highest shortest wavelength Molecules that absorb light are called pigments absorb photons ExampleChlorophyll Indigo Pigments contain alternating double and single bonds and thus many nonbonding electrons These are what interact with the photons of light not required to bond can trap energy ExceptionRetinal involves bonding electrons Pigments are bound very specifically to proteins When you isolate the protein you can keep the pigment attached and the protein has color pigmentprotein complxes The pigment is bound noncovalently to the protein care is required to keep the pigment attached because these bonds are weak Protein electrophoresisMitochondrial proteins run on a gel do not have color so a stain is required to detect them With pigmentprotein complexes there is no need for a stain as the pigment displays color TAKE HOMEPigments are not free they are bound Light AbsorptionAn electron can exist in a ground state or an excited state In chlorophyll there are two excited states If white light is shone on the electron it will be transferred to the higher excited state blue photon or the lower excited state red photon If it is the higher energy state the electron will immediately release heat and move to the lower excited state TAKE HOMEElectrons will always reach the lower excited state ultimately There is not an excited state for green which is why chlorophyll is green One photonOne electron Fates of an electron in the excited stateHeat loss not normally in Chlamy as it functions to retain energy fluorescence release of light fluorescence is of a slightly longer wavelength than the photon as some energy is lost in heat work photochemistry used to change a molecule energy transfer passed to a neighbouring pigment PhotochemistryTakes place in the Photoreceptor isomerization of retinal PhotosynthesisTakes place in the photosystem The chlorophyll are embedded in a protein which surrounds the photocenter Excited chlorophyll is denoted Chl Energy can be transmitted from one chlorophyll into another energy transfer There is no photochemistry occurring no electron movement only excitation through the antenna Photochemistry occurs when the energy reaches the reaction center where photochemistry takes place oxidation of chlorophyll The electron released through this process is used to drive electron transport Rhodopsin Retina discs of the rod photoreceptorRetinal is a pigment surrounded by the protein opsin Retinal is unique because it when it absorbs a photon it transforms from 11cis to alltrans When this conversion happens that form of the pigment detaches from the opsin This is different than a photosystem where the chlorophylls always stay put This changes the opsin which can than interact with the transducin Once it does it activates phosphodiesterase This enzyme cleaves a phosphate bond
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