Biology 1107 Lab 4 Write Up

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Chelsea Ferrer TA: Durning Concentrations of Starch in Protein Solutions Many health supplement companies promote a “pure protein” supplement, with only small amounts of starches used as a homogenization agent and as a method to improve taste. How much is a “small amount” though? Investigating exactly how much of a supplement is starches can give the consumer a better idea at what kind of product they are buying – one higher in protein, or one higher in not so healthy taste. To discover the concentration of starch, absorbance values for each unknown protein solution were compared to a standard curve of a 0.1 g/L stock solution of starch. The (C1)(V1)=(C2)(V2) formula was used to determine how much to dilute the 0.1 g/L stock starch solution. These values produced a standard curve between concentration and their observed absorbance levels in the spectrophotometer. (0.1g/L)(x)=(0g/L)(4mL) X=0mL stock starch *(blank control) 4mL H20 1mL Lugol’s reagent *(must be added for spectrophotometer to read absorbency, not counted in final volume) (0.1g/L)(x)=(0.025g/L)(4mL) X=1mL stock starch 3mL H2O 1mL Lugol’s reagent (0.1g/L)(x)=(0.050g/L)(4mL) X=2mL stock starch 2mL H2O 1mL Lugol’s reagent (0.1g/L)(x)=(0.075g/L)(4mL) X=3mL stock starch 1mL H2O 1mL Lugol’s reagent (0.1g/L)(x)=(0.10g/L)(4mL) X=4mL stock starch 0mL H2O 1mL Lugol’s reagent After creating the known solutions from the concentrations found, the spectrophotometer was zeroed out (see TA for specific instructions on zeroing out spectrophotometer). Each known sample was then placed within the spectrophotometer and the corresponding absorbance levels were recorded and graphed, making a standard curve (see attached graph “Concentration vs. Absorbance”). For each unknown solution, 4mL of each solution was mixed with 1mL of

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