A soil bacterium similar to Bacillus subtilis divides every when grown in a rich medium
PHYSICS · Subjective · Fermi University Physics · Biophysics & Medical Physics · Physical foundations of the living cell · Physical foundations of the living cell
Life at Thermal Energy, Ch The scales of life and the thermal energy
Problem
A soil bacterium similar to Bacillus subtilis divides every 45min when grown in a rich medium. To complete one division it must synthesise a full new set of about 4×106 protein molecules, each on average 320 amino-acid residues long. A single ribosome adds residues to a growing chain at a rate of 12s−1. (a) List the assumptions this estimate needs. (b) Estimate, to one significant figure, how many ribosomes the cell must run at once to finish this protein synthesis within one division cycle. (c) Compare your estimate with the measured ribosome counts the chapter quotes for actively growing E. coli, and say whether the agreement is what an order-of-magnitude estimate should give. (d) In one sentence, connect your answer to part (b) to why a bacterium needs a high surface-to-volume ratio.