The bacterium Brucella abortus imports and uses the unusual sugar erythritol. The concentration of erythritol within the B. abortus cell is 10 mM, but the external erythritol concentration is much lower at 0.20 mM

What is the energy requirement (?G inward in kcal/mol) for the inward transport of erythritol at 37°C under these conditions?
What will be an ideal response?


Answer: Use the equation ΔG inward = RT ln[S] inside/[S] outside.

With the gas constant R = 1.987 cal/mol-K, the absolute temperature T in Kelvin = (°C + 273), [S] inside = 10 mM and [S] outside = 0.2 mM, the above equation becomes:

ΔG inward = (1.987 cal/mol-K) (37 + 273 K) ln(10 mM/0.2 mM)
= 615.97 ln 50 = 2409.69 cal/mol
= +2.41 kcal/mol

Biology & Microbiology

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