CALTECH BI 1 - Lecture notes (36 pages)

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Lecture notes

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Lecture Notes


Pages:
36
School:
California Institute of Technology
Course:
Bi 1 - Principles of Biology

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Dt C Bi 1 Lecture 10 Monday April 17 2005 Diffusion and Molecular Motion in Biology Microscopes 1 Optical microscopy with unstained cells Some microscopes detect the photons that have interacted with biological molecules Some have been absorbed Others have changed phase or velocity and can therefore interfere with photons of unchanged characteristics bright field phase contrast 50 m differential interference contrast Little Alberts Panel 1 1 2 How molecules move in the body m 10 7 10 6 10 5 10 4 10 3 1 m 10 2 10 1 1 1 mm Intracellular capillary spacing Extracellular Diffusion Mechanical Pumps blood brain barrier Lecture 2 3 Diffusion from a Point Source Math 2a will treat probability and statistics Here s a note from a previous core math course Distributions that should be your good buddies Dt C Bionomial see Bi 1 lecture 9 Normal Gaussian see below Poisson C M 8 Dt 3 2 2 r exp 4 Dt C concentration of molecule M initial moles of molecule D diffusion coefficient t time r distance or radius 4 Dt Some diffusion constants and distances C 2 xrms x 2 Dt time to spread t molecular weight MW Diffusion coefficient D m 2 ms x 0 1 m synaptic cleft s x 10 m single cell ms x 1 mm brain region s O2 or Na 32 or 23 1 5 s 50 500 Neurotransmitter or low MW drug 200 0 3 17 s 170 1700 protein 50 000 0 1 50 s 500 5000 5 All I really need to know about life I learned in Bi 1 1 If you want a job done right get a protein 2 Electrical circuits explain many processes 3 Most processes follow an exponential time course 4 Most processes end with a Gaussian distribution 6 Diffusion across the synaptic cleft takes a negligible time at synapses cytosol synaptic cleft cytosol receptor presynaptic terminal postsynaptic dendrite 50 nm transmitter molecules 500 0 05 m receptor receptor Diffusion time a few s direction of information flow 7 from Lecture 5 3 classes of proteins that transport ions across membranes Little Alberts 12 4 Garland Ion channels that flux many ions per event Ion coupled



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