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Biology 1002B
Tom Haffie

Biology Lecture 1 Light EnergyInformationChlamydomonasGreen alga distantly related to plants animalsModel system A sexually active lightharvesting carbonreducing hydrogenbelching planimalEukaryoteAttributes of animal and plants distantly relatedUnicellularLightSource of energy and source of information about environmentCell StructureLarge central Nucleus Two basal body base of flagellacilia develops from this o Where microtubules develop o Sometimes cilia doesnt develop properly in humans due to diseasesERribosomesgolgi o Packaging and sorting of proteinsMitochondria o ATP factory o MultipleA single chloroplast giant o Both MC have a role in energy transduction convert energy from different forms and work pretty closely togethero Pyrenoid site for carbon fixation within Chloroplast o Eyespot within chloroplast but nothing to do with photosynthesis What makes it a good system it is also within Chloroplast outer membrane nothing to do with photosynthesis directly harvests light to orient self in environmentuses it for information and can then swim around helps maximize photosynthesis Orangey cause of carotenoid pigmentSignaling pathway between eyespot and flagellaGood system for genetics cell biology model system which answers questions that cant be found in other complex cells They can be found in the Antarctic below 0but what kind of biochemical adaptations does it have for such harsh environments It is a type of an extremophile o 17m below sea at 2 degrees Evolution of ComplexityMeasures how do we define complexity two components which are combined together more than one entity coming together Defining complexity is hard but measuring is easier o Physical Size How big the Cell isEM takes thin cells10 microns in diameter much bigger than a bacteria which are 1 micron1000 fold volume than ecoli o Genome Size c value paradox however similar organisms can have very different genome sizes so it may not be a good indicatorsometimes works human vs clamy o PCG Protein Coding Genes how many proteins does it code formake o Multicellularity Everything used to be unicellulardifferentiationVolvox has 50 000 cells in one organism outside somatic and inside reproductive cells Single celleat and divideno cooperatingVolvox requires cooperation and making different kind of cells and requires that you dieMulticellularityevolution of deathElectron Microscope o Shows it is 10 micrometers o Looks like there is two chloroplasts when really it is one very large chloroplastPhototaxis movement towardsaway lightClamys want to harvest photons for photosynthesisClamys are a good genetic system you can get mutants in different pathways which allow you to elucidate pathway eyespot and phototaxis what genes are involvedWildtype Run away from the light even though its supposed to run toward Maybe too intense or wrong colorfrequencywavelength cant capture itit can detect it shown because its moving awayMay cause mutationsmutagenic denaturing proteinsIf they harvest too much light it can be damaging even if it is just visible lightBuildup of oxygen reactiveFree radicalsLight can destroy the photosynthetic apparatusIt doesnt want to absorb too much light Eyespot helps measure the amount of light that its getting and can gauge it However it is not like the human eyeComplexity and the Evolution of the eyeEyespot Harvests light detects it converts into electrical response which is transmitted to flagellaEye is much more complex than the Eyespot o It is an image forming eye o It suggests that they share a common ancestor that is very primitive and probably not even as good as the eyespot o This means that these two structures are homologous when a structure shares a common ancestor evolutionary related in terms of proteinsHypothesis Phototransduction How light is used by the eye Anatomy of the EyePhotoreceptor Cells Two typesRods and Cones Modified neurons which sit on the Retinao 6 million cones 120 million rods Mainly rodTheres a photoreceptor that harvests the light a blue dot found on disc many stacks of discs on the rods each photoreceptor tracks the lightOne cell has discs which has photoreceptors a molecule that receives light PhototransductionA protein which sits on the outer membrane of the entire cell plasma membrane Na transporter is on the cellular membrane of the photoreceptor cell disc is inside Pigment when it harvests light it changes The shape changes after from cis to trans retinal what the light is doing and activates a pathway called phototransduction which activates transducinPhototransduction pathway which activates the g protein Transducin which in tern activates the enzyme Phosphodiesterase
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