Investigation - Detection of Proteins by Felix Dyrek

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Felix Dyrek Biological Investigation: Detection of Proteins Introduction: The experiment was performed in order to observe the methods which can be used to demonstrate that proteins are present in different types of food. Research Question: In what kind of foods are proteins present and what kind of techniques are used to prove the presence of proteins ? Hypothesis: If four samples of food, * two of which are known to be rich in protein * and two that lack in protein come into contact with thre
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  Felix Dyrek    Biological Investigation: Detection of Proteins   Introduction:  The experiment was performed in order to observe the methods which can be used to   demonstrate that proteins are present in different types of food. Research Question: In what kind of foods are proteins present and what kind of techniques are used to prove thepresence of proteins ? Hypothesis:  If four samples of food,* two of which are known to be rich in protein* and two that lack in proteincome into contact with three different substances, being:* concentrated nitric acid (xanthoproteic reaction),* potassium hydroxide and copper (II) sulfate, together with potassium sodium tartrate, alsoknown as Biuret reagent , and* ethanol, 89% alcohol by volume (process of denaturation),then, the samples of ham and cheese will react to these substances, while lettuce and applesamples will not. Hypothesis Explanation:  Ham and cheese are rich in protein,lettuce and apple are not.A xanthoproteic reaction will be   produced when the samples which are rich in protein being combined with nitric acid.Its alsocalled ''the xanthoproteic test'' in which a yellow acid substance is formed by the action of hotnitric acid on albuminous or proteid matter. It is changed to a deep orange-yellow color by theaddition of ammonia.In combination with biuret reagent,the blue reagent will turn into violet in case proteins arepresent.  Denaturation will appear when ethanol is added.Denatured proteins exhibit loss of solubility to   communal aggregation.No change will occur if this substances are being combined with the lowprotein food apple or lettuce. Compounds:  * apple* swiss cheese* iceberg lettuce* plain ham* concentrated nitric acid* Biuret reagent* ethanol (89%) Variables:  * three reactant substances* the reaction of the combined protein foods and the substances Apparatus:  * lab apron* gloves* knife* cutting board*12 test tubes* test tube rack  Method:  1.Put on the apron2.Cut the cheese,apple,lettuce and ham small enough that it fits into the test tube  3.Put the test tubes on a test table4.Put the gloves on,take a test tube and fill a small amount of nitric acid into the tube5.Observe what happens and write down your observations6.Do the same with the other test tubes7.Do the same again but this time use the biuret reagent and then the ethanol instead of nitricacid8.Write down your final observations  Data Collection & Processing: Substance   Sample of Food   Observations   Concentrated Nitric Acid   (xanthoproteic reaction)   ham   Sample turned yellow, transparencyincreased   cheese   Turned almost orange, acid turned a bitcloudy   lettuce   No visible reaction   apple   No reaction, except apple turned a bitbrown due to oxidizing with air   Biuret reagent   ham   No visible reaction   cheese   No visible reaction   lettuce   No significant reaction  –  lettuce had atinge of blue   apple   No visible reaction   Ethanol   ham   No visible reaction   cheese   No visible reaction   lettuce   No visible reaction   apple   No visible reaction   Table 1: Reactions observed in the experiment.   Analysis & Conclusion:  In conclusion the results of this experiment dont fit 100% with the suggestions but at least thexanthoproteic reaction prooved the presence of proteins and was therefore succesfull.runninganother experiment with more efficient samples might hopefully let me observe the actually   expactable outcomes.  Bibliography     “ Biuret reagent.” Wikipedia. February 18, 2008. March 2, 2008.<http://en.wikipedia.org/wiki/Biuret_reagent>     “ Denaturation (biochemistry)” Wikipedia. February 9, 2008. March 2, 2008.<http://en.wikipedia.org/wiki/Denaturation>     “ Denature” The Free Dictionary by Farlex. 2003. March 2, 2008. <http://www.thefreedictionary.com/denature>     Dolson, Laura. “List of High - Protein Foods and Amount of Protein in Each.”  About.com: Low-Carb Diets. January21, 2008. March 2, 2008.<http://lowcarbdiets.about.com/od/whattoeat/a/highproteinfood.htm>     “ Low Protein Diets.”  Every Diet. March 2, 2008. <http://www.everydiet.org/low_protein_diets.htm>  
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