Sample Research Paper On The Ability To Taste Phenylthiocarbamide (Ptc) In Relation To A Common Bitter Substance: Coffee (Cuban Coffee And American Coffee)

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Abstract

Different alleles of gene for sensing bitterness have been found. This gene is evolutionary different in chimpanzees and humans and within human populations. Different alleles of the same gene might sense different type so bitter compounds. Here we investigate whether people who have a susceptibility to sense caffeine can also sense the novel compound for bitterness phenylthiocarbamide (PTC).
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There are five basic tastes in humans sweet, sour, salty, bitterness and umami. The taste is only observed on the taste buds of the tongue which detects interactions of different molecules or ions. The sensation of sweetness, bitterness and umami are triggered by G-protein coupled receptors whereas the sour and salty are from induction of hydrogen or alkali metal entering the taste bud cells (Silverthorn, 2009).
Bitterness is peculiarly interesting in that this receptor is largely to warn humans of dangerous toxins in plants and microorganisms. The genes in humans encoding for the GPCR T2R have been found to be TAS2R. However, many humans have pseudogenes in addition to their functional T2R genes. Interestingly, the number of chemicals that can perceive bitter is much more than the number of T2R genes present so each gene many respond to more than one bitter ligand. It has been suggested that different T2R alleles may have different profiles of ligand specificity. Thus, the repertoire of bitter taste receptors may be not limited by the number of the TAS2R genes but instead may involve as many receptors as there are TAS2R alleles. Specifically one gene called TAS2R38 binds to PTC (phenylthiocarbamide) and was discovered in 2003 (Bufe, 2005; Hussain, 2013). There are two commons forms of this gene; tasting allele (T) and non-tasting allele (t). In order to taste PTC, a person only needs one T dominant allele, so people with (Tt) and (TT) are tasters, and people with (tt) are non-tasters. The intensity of how PTC is tasted is due to shape of the receptor protein coded by each allele (Hussain, 2013). The shape of the receptor determines how well PTC binds, and hence produces a stronger bitter taste.
The PTC gene is found in different populations humans and is likely due to differing diets. Humans likely evolved taste differently than chimpanzees as many humans have the ability to taste PTC whereas most chimpanzees do not (Bufe, 2005). These populations were tested using PTC originally to distinguish the genetics of the TAS2R alleles. It was found in several studies that there are distinct differences in different populations e.g. caucasians the frequency of non-tasters is estimated to be approximately 28% overall (Kim, 2004) whereas Japanese may have only approximately 10% non-tasters (Sato, 1997).
However, to determine whether a person is able to test one or another bitter tastes genes would be of potential interest. This could be determined by comparing the tasters to non-tasters of PTC to another bitter compound, caffeine, which is present in different concentrations depending on the preparation methods viz. regular American drip coffee (7 oz 207 ml, 115-175 mg caffeine) and Cuban type espresso (1.5-2 oz, 100 mg ) (Bunker, 1979). Recently, TAS2R43 gene was found to be responsible for sensing bitterness in coffee (Piratsue, 2014). Caffeine and other bitter flavorants may compete with the same bitter receptors as PTC and it has been suggested that the PTC may correlates with behaviors that have important health implications (Floriano, 2006). This competition between bitter flavorants and PTC shown in previous reports (Hall, 1975; Leach, 1986, & Zamora, 1996) have looked into testing the bitter taste of coffee in humans and comparing to other bitter tastes like quinine and PTC.
We aim to look further into understanding the different types of bitterness genes by testing different compounds. In order to determine the sensitivity of bitterness when tasting caffeine, an experiment will be conducted among undergraduate genetics lab students at University (FIU). The relationship between PTC and caffeine will be determined in this experiment. We conducted the study using ## participants in a randomized trial. It can be hypothesized that it a dominant (Tt) student is able to taste caffeine found in coffee then they will have a high chance of being able to taste Phenylthiocarbamide (PTC).

References

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