Chapter 2 – Orientation for the Bio-Curious 57
nine separate fresh uninfected bacterial cultures; all of these subsequently developed
viral infections. The 10th volume was then added to fresh culture medium to make
up to the same 100 μL volume as the original virus culture and mixed. This diluted
virus culture was divided into 10 equal volumes as before, and the previous procedure
repeated up to a total of 12 such dilutions. In the first nine dilutions, all nine fresh
bacterial cultures subsequently developed virus infections. In the 10th dilution, only
six of the nine fresh bacterial cultures developed viral infections; in the 11th dilution,
only two of the nine bacterial cultures developed viral infections; and in the 12th dilu
tion, none of the nine bacterial cultures developed viral infection.
a
Estimate the molarity of the original virus culture.
b
If this culture consisted of virus particles tightly packed, such that the outer coat
of each virus was in contact with that of its nearest neighbors, estimate the diam
eter of the virus. (Hint: a virus culture is likely to cause a subsequent infection of
a bacteria culture if there is at least one virus in the culture.)
2.17 A key feature of biology is that components of living matter appear to have specific
functions. However, the laws of physics are traditionally viewed as being objective and
devoid of “purpose.” Discuss this apparent contradiction.
2.18 Liquid–liquid phase-separated biomolecular condensates appear to have a preferred
length scale in cells, whereas “abiotic” classical nucleation theory for the phase tran
sition process predicts that a transition would, given sufficient time, go to completion
until all the relevant molecules are demixed. What reasons can you think of that could
account for this difference?
2.19 Video-rate fluorescence microscopy with a sampling time of 40 ms per image frame
could track a membrane-integrated protein reasonably well, however, images of a
similar sized fluorescently labeled protein in the cytoplasm using similar microscopy
looked blurry and couldn’t be tracked. Why is this?
REFERENCES
KEY REFERENCE
Alberts, B. et al. (2008). Molecular Biology of the Cell, 5th ed. Garland Science, New York.
MORE NICHE REFERENCES
Banani, S.F. et al. (2017). Biomolecular condensates: organizers of cellular biochemistry. Nat Rev. Mol.
Cell Biol. 18:285–298.
Dawkins, R. (1978). The Selfish Gene, 30th Anniversary ed. (May 16, 2006). Oxford University Press,
Oxford, U.K.
Gibson, D.G. et al. (2010). Creation of a bacterial cell controlled by a chemically synthesized genome.
Science 329:52–56.
Mitchell, P. (1961). Coupling of phosphorylation to electron and hydrogen transfer by a chemi-
osmotic type of mechanism. Nature 191:144–148.
Okuno, D., Iino, R., and Noji, H. (2011). Rotation and structure of FoF1-ATP synthase. J. Biochem.
149:655–664.
Pross, A. (2014). What Is Life?: How Chemistry Becomes Biology. Oxford University Press, Oxford, U.K.
Schrödinger, E. (1944). What Is Life—The Physical Aspect of the Living Cell. Cambridge University
Press, Cambridge, U.K. Available at http://whatislife.stanford.edu/LoCo_files/What-is-Life.
pdf. Accessed on 1967.
Sterelny, K. (2007). Dawkins vs. Gould: Survival of the Fittest (Revolutions in Science), 2nd revised ed.
Icon Books Ltd., Cambridge, U.K.
Wang, J. et al. (2014) Mechanomics: An emerging field between biology and biomechanics. Protein
Cell 5:518–531.