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The Effect Of Caffeine On The Growth Of Bacteria Of The Digestive System

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Extended Essay
Subject: Biology HL
How Does the Presence of Caffeine Affect the Growth of Bacteria of the Digestive System?
Student Name: Bixiang (Sean) Cheng
Session Number: 000537-0010
Supervisor: Ms Julie Cavell

Word Count: 4000 Abstract
Caffeine is the most widely consumed legal psychoactive drug across the world. It is widely used to ward off fatigue and increase focus. Although it is considered to be a harmless substance, and sometimes beneficial, it has been shown that caffeine has antibiotic properties against both beneficial and pathogenic bacteria. This means that regular caffeine consumers could be putting their health at risk by exposing their intestinal bacteria, which provide us with important nutrients, to the antibiotic properties of caffeine. As a result, caffeine consumers may be unknowingly depriving themselves of certain crucial nutrients such as vitamin K2, a substance important in the process of calcium absorption into the bones.
This investigation aimed to determine the effect of caffeine on the growth of bacteria. The research question developed is: How Does the Presence of Caffeine Affect the Growth of Bacteria of the Digestive System? Using agar diffusion test, the effect of caffeine on the growth of bacteria is measured by the zones of inhibition established around the caffeine impregnated filter paper discs. Different concentrations of caffeine were tested, from 0.2 mg/mL to 1.0 mg/mL. The sizes of zones of inhibition was
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