Analytical Biochemistry BCHM 22100
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This 18 page Class Notes was uploaded by Braden Runolfsson on Saturday September 19, 2015. The Class Notes belongs to BCHM 22100 at Purdue University taught by Steven Broyles in Fall. Since its upload, it has received 87 views. For similar materials see /class/207994/bchm-22100-purdue-university in Biochemistry at Purdue University.
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Date Created: 09/19/15
Nicole Coleman BCHM 221 Experiment 3 Qualitative Analysis of Sugars Introduction In the experiment Qualitative Analysis of Sugars we did three tests Benedict s tests Seliqanoff s test and Bial s test on all 12 samples Dglucose Dfructose Larabinose D galactose maltose sucrose Dxylose Dsorbitol Corn starch Sawdust Carrott root and Gum Arabic The Benedict s test is used to indicate if the sugar is reducing the Seliwanoff s test indicates a ketose and the Bial s test indicated a pentose From the experiment we will be able to analyze if each sample is apentose or hexose an aldose or ketose and ifthe sugar is reducing or not Methods In the experiment Qualitative Analysis of Sugars we used 36 test tubes We put 5 drops of each of the 12 samples D glucose Dfructose Larabinose Dgalactose maltose sucrose D xylose Dsorbitol Corn starch Sawdust Carrott root and Gum Arabic in 3 different test tubes and labeled the tube 112 depending on the sample that was in the test tube For the Benedict s test we mixed 1 mL Benedict s reagents into each of the 12 samples and waited 5 minutes The color change from green redbrick will depends on the amount of reducing sugar For the Seliwanoff s test we mixed 1 mL of Seliwanoff s reagent to each of the 12 samples and then heated each mixture in 100 C for 5 minutes Ifthe mixture turned to an orange to red color then the sample tested positive for ketose For the Bial s test we mixed 1 mL of Bial s reagent to each of the 12 samples and heated each mixture in 100 C for 5 minutes If the sample tested positive for pentose then the mixture would turn a green to blue color Results Table 1 Each of the 12 samples and the results for each of the three tests Sample Benedict s Seliwanofl s Bial s arabinose galactose 5 6 Sucrose 7 9 Corn Starch precip l 0 11 Carrot Root yes orange green Discussion Dglucose Dfructose Larabinose HoHI3 0 on HC H no Curt H OH Maltose Sucrose Dxylose OH OH OH L CH CH CH CH V O 2 1 HO OH 1 f H H 0H 0 H I OH H HMOw 0 H O H 0 0 H0 CHZOH HO 0H OH H 0H OH H Dsorbitol DH QH HO TAM DH pentose Sucrose Disaccharide Nonreducing Pentose Ketose DXylose Monosaccharide Nonreducing Pentose Aldose Dsorbitol Monosaccharide Nonreducing Hexose Sugar alcohol Nicole Coleman BCHM 221 Experiment 1 Environmental Effects on pH Introduction In the experiment Environmental Effects on pH we measured the pH on three different concentrations of Tris 1 M 01 M and 001 M to see how dilutions effect the pH ofa solution Also we measured the pH of the 01 M Tris 1 10 dilution at three different temperatures 4 C 22 C and 37 C to see how temperature can affect the pH of a solution The goal of the experiments was to see how pH can be affected by multiple factors Methods In the experiment Environmental Effects on pH four 100mL beakers and four stir bars were used for the dilutions of 1 M Tris and one beaker contained 1 M Tris Three of the four beakers were prepared with a 110 dilution of Tris 5mL of Tris and 45mL of H20 and one beaker with a 1100 dilution of Tris 05mL of Tris and 495mL of H20 The 110 dilutions were separated one was put in an ice bath 4 C one was put in a steam bath 37 C and the last was kept at room temperature 22 C and we allowed 30 minutes for the temperatures to equilibrate The pH meter was standardized prior to lab We first measured the pH of the 1M Tris solution and after 30 minutes we measured the pH of the three 1 10 diluted solutions 4 C 22 C and 37 C by checking the temperature with a thermometer prior to measuring the pH and gently stirring the solutions during pH measurements We also read the pH of the 1 100 dilution by stirring while measuring the pH Results Table 1 Dilutution vs pH Dilution pH 11 78 110 795 1100 77 Table 2 Temperature vs pH of the 110 dilution Temperature pH 40 8 Table 3 Classmates Concentration vs pH Concentraion 1 M Tris 01 M Tris 001 M Tris pH 78 80 77 pH 82 77 76 pH 79 785 78 Graph 1 pH vs Tris pH vs Tris l M 01 M 001 M Tris M Graph 2 pH vs Temperature pH vs Temperature in 110 Dilution pH 4 22 37 Temperature C Discussion Our pH vs dilution did not come out as predicted We predicted the pH would decrease as the solution became more diluted but our 110 dilution had a higher pH then the 1 M Tris The majority of our classmates were able to get our prediction This couls have been caused by a difference in standardization of pH meters of ours compared to the TA s whom prepared the l M Tris solution for the class We should have seen a decrease in pH as the Molarity decreased and we can predicted this by the formula pKa PIsz which concentration shifts pKa so the higher the concentration of Tris the higher the pH Our pH vs temperature accurately worked we were able to get a stead decrease of pH as the temperature increased Temperatures effect ionization so with a decreased in temperature there is less ionization of the solution Also the pH meter measures in volts and from the 23RTpH F we can see that when temperature decreases pH must increase to keep equation V E the voltage the same Nicole Coleman BCHM 221 Experiment 2 AcidBase Chemistry in Water Introduction In the AcidBase Chemistry in Water experiment We made 3 titrations of pure water 04 M glycine and 24pentanedione with KOH to test the effects of polarization of a carbonoxygen bond and the effects of hydroxyl ions on the pH of a solution We tested pure water to show the increase in pH with no impediment of a buffer Then we titrated 04 M glycine to illustrate the difference in pH effect when a significant amount of buffer is present in a solution Finally we titrated 24pentanedione to illustrate the effect of polarization of a keto group We Methods We started with 40 mL of water H20 ofa pH of 15 in a 100 mL beaker and a stir bar then we place the beaker on a stirring plate by a pH meter We rinsed the pH meter s electrode with water dot dried it and then inserts it into the beaker that neither the stir bar or side of the beaker is touching it The solution was slowly stirred and then the pH was recorded Then 02 mL of KOH was added the solution was waited on until the pH stabilized and finally the pH was recorded KOH was added to the water until the pH ended up being over 12 After water was titrated to over a pH of 12 we titrated 04 M of glycine and 24pentanedione with KOH the same way but with 05 mL of KOH was added each time until both of the solutions reached over a pH of 12 Results Table 1 pH Titration of Water H20 KOH added mL pH 0 15 02 16 40 119 42 12 Table 2 pH Titration of Glycine KOH added mL pH 0 15 05 165 Table 3 pH Titration of 24 pentanedi0ne KOH added pH Graph 1 Titration of H20 pH of Water Titration OpH 0 002 004 006 008 01 KOH M Graph 2 Titration of Glycine pH of Glycine Titration pKa 235 K0H1M Graph 3 Titration of 24 pentanedione pH of 24Pentanedione KOH M Discussion We can account for the signi cantly different responses of titration of water and glycine because water is a strong polar molecule due to the Hbonding Glycine does not have the same polarity but has two different resonance structures that can account for it s two different pKa s Also water does not contain a carbonoxygen bond so polarization will take place later on resulting in a spike of pH The pKa of 24pentanedione is about 9 The only error that could have been made is adding too much KOH or accidently not adding enough One extra drop located on the pipette tip could cause the pH to change dramatically without that drop being accurately accounted for Ionic forms of glycine a le b pH6 c pH 11 Glycine with no charges will ever exist in water pH of 6 Equation Resonance structure of 24 pentanedione