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Lecture outcomes.docx

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Western University
Biology 1002B
Tom Haffie

Lecture 1: Intro and Chlamydomonas January-21-13 4:32 PM 1. Roles of light as used by life  Photosynthesis and carbon fixation 2. Characteristics of Chlamydomonas that make it a useful model system  a sexually active, light harvesting, carbon-reducing, hydrogen belching planimal  function of basic components of Chlamydomonas cells  Large central nucleus  2 basal bodies  Flagella develop from this organelle  Endoplasmic reticulum  Ribosomes  Golgi app.  Mitochondria  One chloroplast  Pyraniod  Center of carbon fixation Co2 --> organic  Eyespot  Harvests light (not to do is photosynthesis)  Chlamydomonas are extremophiles  relative usefulness of various biological characteristics as measures of complexity  How large a organism is  Genome size o C value paradox o PCG - protein coding genes  Rise of multicellularity and eukaryote advantages to Chlamydomonas in being phototactic.  Respond to fluctuating light levels which is there primary source of energy reasons why Chlamydomonas might move AWAY from a light source.  Wrong colour, too much energy  Denature proteins  Destroy photosynthetic apparatus basic structure of rods and cones as photoreceptor cells.  Rods --> black/white  Cones --> colour  Rods and cones are photoreceptor cells o Sit on retina  Located in discs which are in the eye major components involved in phototransduction and their role.  Phototransduction: o One photon changes from cis-retinal to trans-retinal  Transducin activates a phosphodiesterase which breaks a bond in cyclic GMP Lecture 2: Light - Energy and Information January-21-13 4:43 PM 1. Relationship between excited states of a pigment and its absorption, fluorescence emission spectra.  2. Region of the electromagnetic spectrum known as “visible light”.  Wavelength of 400nm (violet, more energy) to 700nm (red, less energy).  Ultraviolet comes before, infrared comes after  Relationship between wavelength and energy content of a photon.   Molecular characteristic of visible pigments that make them able to absorb light.  Pigments absorb light (ex. Chlorophyll)  Non bonding / pi orbital electrons can trap light  Conjugated ring system = absorb light?  Relationship between pigments and associated protein.  Pigments are bound to proteins non-covalently o This produces pigments-protein complexes  Gel electrophoresis resolves pigment-protein complexes  Four “fates” of the excited state of chlorophyll resulting from absorption of photons.  Decay, Heat, Fluorescence, Photochemistry and Energy Transfer  Reason(s) why relative fluorescence is different in isolated chlorophyll vs. intact cells when exposed to light.  Sfdjlds;afffffffffff  What accounts for the fact that chlorophyll is green in colour  Chlorophyll is green because there is no excited state that absorbs green  Quantitative relationship between photons and excited electrons.  sadffffffffffff  Relationship between energy of photon and energy required to excite electrons in order for photons to be absorbed.  asdfffffffffffffffffffff  General structure of photosystem.  Antenna outside, reaction center in middle  Energy transfer occurs in antenna  Similarities and differences of the light capturing and photochemistry of phototransduction (retinal) vs. photosynthesis (chlorophyll).  Photochemistry takes place at photoreceptor o Isomerization of retinal  How are excited states of antennae pigments organized to provide for energy transfer to reaction center.  Reaction (antenna): Chl+ + Chl --> Chl + Chl+ o Not oxidation/reduction reaction o Not photochemistry  Reaction in reaction center: Chl+ --> Chl+ + e- o Used for electron transport  Structure of rhodopsin.  Rhodopsin = retinal + opsin: o Retinal = pigment, opsin = protein o Double bond prevents rotation (Cis/Trans)   Effect of photon absorption by 11-cis retinal on retinal structure followed by association with opsin protein followed by interaction of transducin with opsin.  11 cis (dark) changes to all trans retinal when light hits it  This is called photo-isomerization (double bond breaks and then reforms)  This process is spontaneous, very rare to occur without light  Transducin can only gain access to the rodopsin when trans is active, in cis the binding site is not accessible  Reasons why life has evolved to detect the narrow band of energy represented by “visible light”.  Everything in bio that uses light uses visible light  Visible light is the most dominant form of EM radiation  Energy in visible light is perfect for exciting electrons o Enough energy to drive photochemistry Lecture 3: Protein Structure and Function January-21-13 5:06 PM 1. reasons why photosystems have antenna proteins while the eye doesn’t.  2. points of control for regulation of protein abundance.  Transcription  Transc
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