BIOL 2021 Lecture Notes - Lecture 13: Transducin, Phosphodiesterase, Rhodopsin
13 May 2018
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• Signalling cascade (848)
o Enzymatic cascade > amplification.
• Fig 15-41 amplification in light transduction:
o Rhodopsin molecule absorbs one photon.
o 500 G proteins (transducin) molecules are activated.
o 500 cyclic GMP phosphodiesterase molecules are activated.
o 10^5 cGMP molecules are hydrolyzed.
o 250 cation channels close.
o 10^6-10^7 Na+ ions per second are prevented from entering the cell for a
period of around 1 second.
o Membrane potential is altered by 1 mV.
o Signal relayed to brain.
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