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Unformatted text preview: Solutions to the Midterm (BENG 351 Fall 2007): Problem 1: a) Because the displacment of the organism is constant with time, whereas the cloud moves at a speed which is inversely proportional to sqrt(time). b) For organism: u o =x/t; for cloud u = 2 D t 1/ 2 . Equating both: gives t = 2 D u 2 c) Let u =10L. The longer the organism the quicker it gets (easier for it to win the race). d) Virus: 0.2 sec, Bacteria: 0.0005 sec. Crustacean: 2E-9 sec. (100 nm=100E-9 m = 1E-5 cm). e) BONUS: Does not need it.. Diffusion is an enough means for it to get its nutrition. Motility involves energy expenditure which is not warranted. Problem 2: a) D 1 r 2 d dr r 2 dC dr = ∂ C ∂ t = b) r=r d---C=0 r infinity----C=C C) Solving using the B.Cs: C ( r )= C o (1-r d /r) D) Flux= -D(dC/dr)= D(C o r d /r 2 ) E) Larger the cell the slower the flux. The flux is moles/unit area per time....
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This note was uploaded on 09/24/2009 for the course BENG 351 taught by Professor Ericstern during the Fall '08 term at Yale.
- Fall '08