The kidneys are the main organs of the urinary system. They function chiefly to filter blood in order to remove wastes and excess water. The waste and water are excreted as urine. The kidneys also reabsorb and return to the blood needed substances, including amino acids, sugar, sodium, potassium, and other nutrients.
But many popular brands actually contain considerably less than an old-fashioned cup of black coffee. An 8.4-ounce serving of Red Bull, for instance, has a relatively modest 76 to 80 mg of caffeine, compared to the 95 to 200 mg in a typical cup of coffee, the Mayo Clinic reports.
How much caffeine is in a cup of coffee? Pop Quiz. How much caffeine is in a cup of coffee? a) 2 to 12 mg per cup. b) 140 mg per cup. c) 330 mg per cup. d) It depends. If you answered âAââyou are drinking decaf. Answer âBâ is the average caffeine content for an average size cup of brewed coffee.