Biology 1001A Lecture Notes - Lecture 2: Visual Phototransduction, Carotenoid, Bioluminescence
24 Apr 2016
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Bio 1002b lecture 2 january 9, 2014. Quanta (discrete packages) of light = photon (particle) Energy is inversely proportional to wavelength: blue light (400nm) high energy, red light (700nm) low energy. Molecular characteristic of pigments that make them able to absorb light: pigments absorb light, proteins don"t. Absorption of a photon excites an electron in pigment molecule. Why is chlorophyll green: energy absorbed by photon must match the energy required to get the electron to an excited state, chlorophyll has excited states for blue and red light, but not green. Reflects green light, so we see green. What is the light actually doing: photoisomerization (turning trans isomer into cis) (not photochemistry because only switching isomers, changes conformation of protein. Eyespot structure and directional movement: chr1 and chr2 photoreceptors on plasma membrane, carotenoid (pigment)-filled globules, tells cell where light is coming from, light cannot hit photoreceptors from back side (through globules)
