BCH 2333 Lab 1: Carbohydrates Study Guide with Complete Solution |
2026 Update
LAB 1: Carbohydrates
TA: Andrew Hainer
January 16, 2026
100/100 total (great job!)
Purpose:
The purpose of this lab was to explore the different properties that carbohydrates display. Specifically, in
this lab, the molecular weight of monosaccharides and polysaccharides were examined. This was done
through a variety of techniques. The first being dialysis which was used to separate glucose from starch
by selective diffusion. Gel-filtration chromatography was also used as a separation technique as larger
molecules such as starch can pass through the column containing hydrated beads faster than smaller
molecules. Colorimetric assays can then be utilized to measure the concentration of the respective
carbohydrates present. The glucose oxidase assay was used to observe the presence of glucose. The iodine
reaction assay was used to observe the presence of starch. Thus, the knowledge of the difference between
the molecular weight of glucose and starch can be used to isolate them from an initial mixture containing
both.
Results and discussion:
, R1.
Table 3. Initial and final concentrations of glucose and starch present in the internal and external
solution before and after the completion of dialysis. 10 mL of the initial glucose/starch mixture was added
to a dialysis bag and placed in 200 mL of water. The dialysis system was left for a total of 47 minutes. The
glucose standard and starch standard solutions have concentrations of 1.5 mg/mL and 0.20 mg/mL,
respectively. The complete glucose oxidase-peroxidase assay consists of 0.004 mg/mL glucose oxidase,
0.02 mg/mL peroxidase, and 0.01 % tolidine in 0.15 M acetate buffer at pH 5.0. For starch an iodine assay
was used composed of 5mM I2 and 10 mM KI. 1.2 mL of the glucose oxidase-peroxidase reagent and 75
µL of the iodine solution were added separately to different test tubes containing samples of the glucose
standard, starch standard, initial mixture, final internal solution, and final external solution. After the
glucose oxidase reaction was left to incubate for 10 minutes at room temperature 0.1 mL of 2N H2SO4 was
added to stop the reaction. Absorbance was measured at a wavelength of 420 nm (A420) for solutions
containing the glucose oxidase-peroxidase reagent and 600 nm (A600) for solutions containing the iodine
solution.
Analysis:
The dialysis of the initial starch/glucose mixture was conducted in a closed system. Thus, after dialysis is
complete the mass of the solutes at the end should remain the same. Glucose should diffuse into the
external environment out of the dialysis bag until equilibrium is reached. The total mass of glucose present
at time 0 was 466 mg and the total mass at the end was 484 mg. The end mass is similar to the original
mass of glucose, however; it is slightly larger, approximately a 4% increase. This could be due to
inaccuracies with absorbance measurements. Ideally, starch should not be able to leave the membrane
due to its high MW (molecular weight). However, the mass of starch at the start and end of dialysis does
differ by 0.25 mg. This indicates that some mass diffused to the external solution, however; the corrected
absorbance value for the external solution of starch was 0. This indicates that very little starch diffused
out of the dialysis bag. The initial and final values for the mass of starch are also quite similar.
Sample Calculations :
Concentration of glucose:
Ab/Cb = Ad/Cd Variables:
(Ab)(0.025/0.6)( Cd) = (Ad) (Cb) Correction of absorbance: Cd = (0.386*1.5 g/L)/(0.298
*(0.025/0.6)) Ab = 0.308 – 0.010 = 0.298
2026 Update
LAB 1: Carbohydrates
TA: Andrew Hainer
January 16, 2026
100/100 total (great job!)
Purpose:
The purpose of this lab was to explore the different properties that carbohydrates display. Specifically, in
this lab, the molecular weight of monosaccharides and polysaccharides were examined. This was done
through a variety of techniques. The first being dialysis which was used to separate glucose from starch
by selective diffusion. Gel-filtration chromatography was also used as a separation technique as larger
molecules such as starch can pass through the column containing hydrated beads faster than smaller
molecules. Colorimetric assays can then be utilized to measure the concentration of the respective
carbohydrates present. The glucose oxidase assay was used to observe the presence of glucose. The iodine
reaction assay was used to observe the presence of starch. Thus, the knowledge of the difference between
the molecular weight of glucose and starch can be used to isolate them from an initial mixture containing
both.
Results and discussion:
, R1.
Table 3. Initial and final concentrations of glucose and starch present in the internal and external
solution before and after the completion of dialysis. 10 mL of the initial glucose/starch mixture was added
to a dialysis bag and placed in 200 mL of water. The dialysis system was left for a total of 47 minutes. The
glucose standard and starch standard solutions have concentrations of 1.5 mg/mL and 0.20 mg/mL,
respectively. The complete glucose oxidase-peroxidase assay consists of 0.004 mg/mL glucose oxidase,
0.02 mg/mL peroxidase, and 0.01 % tolidine in 0.15 M acetate buffer at pH 5.0. For starch an iodine assay
was used composed of 5mM I2 and 10 mM KI. 1.2 mL of the glucose oxidase-peroxidase reagent and 75
µL of the iodine solution were added separately to different test tubes containing samples of the glucose
standard, starch standard, initial mixture, final internal solution, and final external solution. After the
glucose oxidase reaction was left to incubate for 10 minutes at room temperature 0.1 mL of 2N H2SO4 was
added to stop the reaction. Absorbance was measured at a wavelength of 420 nm (A420) for solutions
containing the glucose oxidase-peroxidase reagent and 600 nm (A600) for solutions containing the iodine
solution.
Analysis:
The dialysis of the initial starch/glucose mixture was conducted in a closed system. Thus, after dialysis is
complete the mass of the solutes at the end should remain the same. Glucose should diffuse into the
external environment out of the dialysis bag until equilibrium is reached. The total mass of glucose present
at time 0 was 466 mg and the total mass at the end was 484 mg. The end mass is similar to the original
mass of glucose, however; it is slightly larger, approximately a 4% increase. This could be due to
inaccuracies with absorbance measurements. Ideally, starch should not be able to leave the membrane
due to its high MW (molecular weight). However, the mass of starch at the start and end of dialysis does
differ by 0.25 mg. This indicates that some mass diffused to the external solution, however; the corrected
absorbance value for the external solution of starch was 0. This indicates that very little starch diffused
out of the dialysis bag. The initial and final values for the mass of starch are also quite similar.
Sample Calculations :
Concentration of glucose:
Ab/Cb = Ad/Cd Variables:
(Ab)(0.025/0.6)( Cd) = (Ad) (Cb) Correction of absorbance: Cd = (0.386*1.5 g/L)/(0.298
*(0.025/0.6)) Ab = 0.308 – 0.010 = 0.298
