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The water flea Daphnia performs a reasonably constant number of heartbeats and t

ID: 617058 • Letter: T

Question

The water flea Daphnia performs a reasonably constant number of heartbeats and then dies. These fleas live twice as long at 15oC as at 25oC. A)Estimate the activation energy for the reaction that controls the rate of the heartbeat. k = A EXP(-Ea /RT) k(25oC) / k(15oC) = EXP [-Ea/R (1/298 - 1/288)] = 2 -Ea/R (1/298 - 1/288) = ln 2 Ea = 4.9x104 J/mol (or 49 kJ/mol) B) If a related species had a catalyst in its system that lowered the activation energy for the reaction that controls the heartbeat, would it have a longer or shorter lifespan at 25C than the Daphnia flea (relative to the lifespan at 15C)?

Explanation / Answer

The water flea Daphnia performs a reasonably constant number of heartbeats and then dies. These fleas live twice as long at 15oC as at 25oC. Estimate the activation energy for the reaction that controls the rate of the heartbeat.
    k = A EXP(-Ea /RT)
    k(25oC) / k(15oC) = EXP [-Ea/R (1/298 - 1/288)] = 2
    -Ea/R (1/298 - 1/288) = ln 2
    Ea = 4.9x104J/mol   (or 49 kJ/mol)