Running away from a tiny monster

You've become infected by the newly discovered bacterium Diarrhea ultradanger . The mode by which D. ultradanger attacks the body is by producing a harmful type of molecule called enterotoxin.

As a defense, your doctor prescribes you the antibiotic medicine chloramphenicol which reaches a concentration c 0 c_0 in the bloodstream upon administration. However, being a highly successful pathogen, D. ultradanger can destroy molecules of chloramphenicol by producing the enzyme chloramphenicol acetyltransferase (CAT) and exporting it into the bloodstream. If D. ultradanger can manage to keep CAT at the concentration c 0 c_0 in the bloodstream, it will escape the drug treatment and cause awful diarrhea. As a further counteraction, the body can degrade molecules of CAT at a rate β deg \beta_\text{deg} .

If β deg = 5 s 1 \beta_\text{deg} = 5 \text{ s}^{-1} , and c 0 = 17 mM c_0 = 17 \text{ mM} , what is the minimum rate (in mM/s \text{mM/s} ) at which the D. ultradanger cells must produce CAT in order to escape the drug treatment?


The answer is 85.0.

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1 solution

Himanshu Arora
Jun 17, 2014

At equilibrium the concentration of CAT must be c 0 = 17 m M {c}_{0} = 17mM . Thus the rate at which CAT is degraded by the body is r a t e d e g = β d e g × c 0 = 85.0 m M / s {rate}_{deg}={\beta}_{deg}\times {c}_{0} = \boxed{85.0 mM/s} . Thus D. ultradanger must produce chloramphenicol acetyltransferase at the same rate, for the least case.

The unit of degradation does not match with the units used. You say that the degradation is by number of molecular units per second, while the other quantities are in molars (moles/L). Though it wouldn't really make sense if we be really strict about the units used, I suggest you change how the quantities are presented to avoid any similar confusion.

Miguel Yorro - 6 years, 11 months ago

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Sorry, to be clear, it wasn't really said that the unit of degradation is number of molecular unit per second. It was implied. Or at least, ambiguous.

"... degrade MOLECULES of CAT at the rate..." -> this phrase kind of makes theambiguity.

Again, I know that the problem will not make practical sense if we use the units I said. But I suggest you clarify the units anyway to avoid this kind of ambiguity.

Miguel Yorro - 6 years, 11 months ago

exactly... so i thought 5 molecules wrt a mole i.e. 10^23 molecules is irrelevant ... then the answer comes out to be Co

aroop kundu - 6 years, 11 months ago

Does it matter how fast each cell of D. ultradanger makes CAT or just the population?

Josh Silverman Staff - 6 years, 11 months ago

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