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Biology 1002 Lectures 1 - 9 Outcomes

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Biology 1002B
Tom Haffie

Lecture 1 Outcomes 1 Function of basic components of Chlamydomonas cellsNucleussimilar to the nucleus of a humanplantanimal cellHas a basal bodyfound at the base of the flagellumwhere the microtubules develop MitochondriaATP factory of the cellChloroplast o Inside the chloroplast is a reigion called the pyrenoidWhere carbon fixation takes placeEnergy transductionchloroplast and mitochondria work closely togetherEye spotorangey in colour because of a pigment called carotenoid o Found within chloroplast but not directly related to photosynthesis o Enables the cell the orientate itself in relation to light2 Relative usefulness of various biological characteristics as measures of complexityCell sizeo Chlamy is 10 microns in diameter much bigger than a bacteriumGenome size o In many cases it isnt a good indicatorcan mislead youPCGProtein Coding Genes o How many proteins do your genes code forRise of Multicellularity o Volvox50 000 cells in one organismSomatic cells on the outside and reproductive cells on the centre 3 Advantages to Chlamydomonas in being phototacticChlamy uses its eyespot for phototactics the movement towards or away from lightIt wants to move towards light because they want to harvest photons for photosynthesis 4 Reasons why Chlamydomonas might move AWAY from a light sourceRunning away from bright light suggests light may destroy the photosynthetic apparatus by creating free radicals ROSreactive oxygen speciesThe idea that light can be harmful even if its in the visible spectrum 5 Basic structure of rods and cones as photoreceptor cellsThere are two types of photoreceptor cells rods and cones o They are modified neurons o They sit on the retinaThe rod is made up of disks which has many individual photoreceptors o Blue dots on the disks o It is the photoreceptor that tracks the light6 Major components involved in phototransduction and their rolePhoton changes the shape of the photoreceptor from cisretinal to transretinal and activates a pathway called phototransduction o Activates a protein called transducing which activates an enzyme called phosphodiesteraseThe sodium transporter is on the plasma membrane of the photoreceptor cellThe sodium pump is regulated by cyclic GMP o When cGMP is bound sodium is transported into the cellsodium influxcGMP is bonded to the 3 and 5 position and the G protein activates phosphodiesterase which breaks the bond in cyclic GMPphosphodiesterase cleaves the 3 end so it is only bound on the 5 end which generates 5GMP and the consequence of that is the transporter turns off and shuts off the sodium pump o the consequence of that is the membrane hyper polarizesthe voltage across it becomes even greaterin the light the membrane hyper polarizes which leads to an electrical signal being sent down the membrane surrounding the photoreceptor cell200 million bits per second move along the optic nerve to the brain Lecture 2 Outcomes 1 Relationship between excited states of a pigment and its absorption fluorescence emission spectraWhen a pigment absorbs a photon of light an electron in the pigment is excited from the ground stateIf it absorbs a higher energy photon of light ie Blue it will be excited to the higher excited state but will decay very quickly to the lower excited stateIf it absorbs a lower energy photon ie Red it will be excited directly to the lower excited stateWhen the electron falls from the lower excited state some energy is lost as heat but the rest through fluorescence o The fluorescence will be a longer wavelength that the original light because some energy has been lost to heat o The longer wavelength will cause the colour to be slightly different than the original photon absorbed 2 Region of the electromagnetic spectrum known as visible lightThe most abundant form of light on the surface of the Earth and is the light that can be detected by the human eye ROYGBIVTypically absorbed and emitted by electrons in molecules and atoms that move from one energy level to anotherThis action allows the chemical mechanisms that underlie human vision and plan photosynthesis 3 Relationship between wavelength and energy content of a photonThe wavelength and the energy of a photon are inversely proportional o The shorter the wavelength the higher the energyGamma rays have short wavelength radio waves have long wavelength4 Molecular characteristic of visible pigments that make them able to absorb lightMolecules that absorb light are called pigmentsThey have a conjugated system o Alternation between a double and a single bondIt indicates a certain kind of electron configurationnonbonding Pi orbital electrons o It is those electrons that are going to interact with the photons of light An exception is retinalit does have a role in bonding 5 Relationship between pigments and associated proteinWhether it is chlorophyll or retinal these pigments are not free they are bound very specifically to proteinsIf proteins and pigments are bound when you isolate the protein you can actually keep the pigment attached o It is bound noncovalently to the protein If you isolate mitochondrial proteins you dont see anything when you put them through the gel electrophoresisthey dont have any pigment so you have to stain the gel 6 Four fates of the excited state of chlorophyll resulting from absorption of photonsCan lose it all as heatthe higher state can simply decay and you lose the energy o In Chlamy if you lost all the energy to heat the cell would die
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