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Biology 1200B notes

60 Pages
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Department
Biology
Course Code
Biology 1002B
Professor
Tom Haffie

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Biology Lecture 1Chlamydomonas Roles of light as used by lifeLight is used as a source of energy and as a source of information about the environment Characteristics of Chlamydomonas that make it a useful model system Genome sequence is useful to study because it has attributes of both animal and plant cells Some human diseases are caused by mutations that make the cilia in humans develop poorlyChlamy is helpful for looking at agella and cilia structure and function because it is a eukaryote and the agella is identical in chlamy as it is in humans Good for looking at light energy and information because it has an eyespot that detects light and then orients chlamy in relation to the light can either swim towards light or away from it Has a good genetic system that has mutants in different pathways mutants enable you to elucidate the pathway We want to elucidate the pathway betweenthe eyespot and the photoaxiscells movement in relation to where the light comes from to nd out which genes are involved in light reception and controlling the agella so that the cell moves It is homologous with the human eye this is just a hypothesis Function of basic components of Chlamydomonas cellsNucleusgene expressiontranscription Basal Bodyorganelle found at the base of any agellum Where the microtubules develop to produce the agella Ribosomesite of protein synthesisMitochondriaATP factories of the cellhas more than one mitochondria Chloroplastenergy transducing factory of the cell just 1 cholorplast Within cholorplast is pyrenoidwhere carbon xation takes placeOccurs in Calvin Cycle Carbon xationprocess by which photosynthetic organisms such as plants turn inorganic carbon ieCO2 into organic compounds iecarbs Also within the chloroplast is the eyespotenables single chlamy cell to orient itself in relation to light Relative usefulness of various biological characteristics as measures of complexityCell sizeHuman cellsChlamyEcole the bigger the cell the more space it needs to carry out complex processes and compartmentalizeGenome sizecan be useful sometimes although some similar organisms have very different genome sizes some inconsistencies Protein coding genes PCGHow many proteins does your genome code forBoth genome size and PCG can be misleading due to junk DNAetc Advantages to Chlamydomonas in being phototacticEyespot is used for photoaxismovement towards or away from light Chlamy can thus move toward light because they want to harvest photons for photosynthesis Reasons why Chlamydomonas might move away from a light sourceIf too much light is absorbed too much product is formed and as a result too much oxygen is formed and this can lead to reactive oxygen species which can destroy the cell if theres too many of them Basic structure of rods and cone as photoreceptor cells Photoreceptor cells rods and cones havephotoreceptors which are the blue dots found on the disk which harvest the light there is a stack of disks making up rods and cones and each disk has many photoreceptors and these individual photoreceptors trap the lightMajor components involved in phototransduction and their role Pigment found within the discs change when light is harvested this changeactivates a pathway called phototransductionwhen this pathway is active itactivates another proteintransducinSO the membrane complex grabs the photon of light which causes achangein the discs that then activates transducin which in turn activatesthe enzyme phosphodiesteraseThe sodium pump located on the membrane is regulated by cyclic GMP So when cyclic GMP is bound sodium is transported into the cell andthere is a sodium inux excessThe phosphate group in cyclic GMP is bound to the ribose of GMP atthe 5 and 3 position SO when phosphodiesterase cleaves the 3bond a 5GMP is generatedThis results in the cyclic GMP detaching from the transporter andas a result the transporter SHUTS OFF and sodium cannot enterthe cellLight through the processes mentioned above shuts down thesodium pump which hyper polarizes the membrane whichleads to an electrical signal being sent down the membranesurrounding the rod or coneThe signal moves along the optic nerve and reaches yourbrain at an incredibly fast speed as a result you see
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