Biology 1002B Lecture Notes - Photochemistry, Chlamydomonas, Transducin
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Lecture 1: Intro and Chlamydomonas
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
Center of carbon fixation Co2 --> organic
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
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
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.
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
1. Relationship between excited states of a pigment and its absorption, fluorescence
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
Decay, Heat, Fluorescence, Photochemistry and Energy Transfer
Reason(s) why relative fluorescence is different in isolated chlorophyll vs. intact
cells when exposed to light.
What accounts for the fact that chlorophyll is green in colour
Chlorophyll is green because there is no excited state that absorbs green