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Why do they put mint in toothpaste? Would garlic be better?

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Why do they put mint in toothpaste? Would garlic be better? Hypothesis I already know from reading the passage titled "Antibacterial Chemicals" on activity 4.7 that both mint and garlic contain antibacterial properties. After reading through the procedure I expect to see a larger zone of inhibition caused by mint than by garlic - this is because mint is used in toothpaste and other treatments such as "Bonjela" and contains menthol which can act like a local anaesthetic. Method We used the procedure outlined on activity 4.7 but with a few changes: * We used 1.5g of plant material between 4 people and only 5cm3 of methylated spirit instead of what is outlined in step 2. * We dipped the sterilised paper discs into the plant extract using tweezers instead of pipetting it as outlined in step 3 * We did not use other plants as outlined in step 5 Also: * We decided that the control should be the methylated spirit * We used sterilised discs cut from filter paper instead of the Whatman antibiotic assay paper discs * The agar jelly had already been poured into sterile Petri dishes for us Safety * We followed normal laboratory rules e.g. ...read more.


that both of the plants had antibacterial properties and that the substance killing the bacteria is active in the plants and is not the methylated spirit used. My results also show that mint has slightly better antibacterial properties than garlic which supports my hypothesis; although since writing my hypothesis my biological knowledge has grown and I have done some further research using information from textbooks and my teacher and my knowledge now contradicts this. Garlic has an active ingredient called allicin which is produced when the garlic plant is cut or damaged (as we have in the experiment by using the pestle and mortar) and the enzyme allinase converts alliin to allicin. This allicin destroys bacteria such as Campylobacter and Heliobacter and interferes with lipid synthesis and RNA production. Mint produces menthol and carvone which although are toxic to microbes and insects are also used in flavourings by humans. Although mint numbs the human mouth and does kill some bacteria, if garlic was used it would destroy more. But for obvious reasons such as bad breath mint is used instead of garlic. ...read more.


* My results are not very precise either as my repeats are far away from each other e.g. 15mm and 20mm for Garlic. How to make more reliable If I repeated this experiment I could prevent these errors by using more accurate scales with a smaller percentage error and to a higher decimal place. I would also leave the discs in the solution for a set amount of time to allow them to all become saturated in solution before being placed on the agar jelly. I would not use any discs that had any matter on them. I would also use more sets of data to prove/disprove my conclusion. To measure the zone of clearance more accurately I would agree to use the largest/smallest part or use a piece of string placed on the Petri dish and marked where the zone reached to compare all three against each other. I would also leave the experiment for longer for the active ingredient to diffuse. But I would have to do some preliminary work to see for how long I could leave the bacteria and low long I could leave it before different zones of different substances meet as then the experiment would be invalid. ...read more.

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