High doses of caffeine interfere with the dna replication checkpoint mechanism in mammalian cells. why then do you suppose the surgeon general has not yet issued an appropriate warning to heavy coffee and cola drinkers? a typical cup of coffee (150 ml) contains 100 mg of caffeine (196 g/mole). how many cups of coffee would you have to drink to reach the dose (10 mm) required to interfere with the dna replication checkpoint mechanism? (a typical adult contains about 40 liters of water.)

Molarity = 

Moles of Caffeine = Mass of Caffeine/Molar Mass
Mass = 100 mg = 0.1 g
Molar Mass = 196 g/mole

Moles of Caffeine in one cup = 0.1/196 moles
= 5.102 * 10^-4 moles

If one cup of coffee is ingested (A typical adult contains about 40 liters of water),

Molarity of caffeine = [(5.1 * 10^-4)/ 40] M
= 0.012755 mM

The toxic molarity of caffeine in the body 10mM

How many cups will be toxic?
= Toxic Molarity/ Molarity of 1 cup
= 10/ 0.012755
= 784

In other words, you would have to drink 784 cups of coffee to reach the dose required to interfere with the DNA replication checkpoint mechanism.