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Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry Essay Example

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Griffith University (GC Campus)

Chemistry of Biological Systems 1015MSC


Angelina Ho

Determination of Glucose in Coke and Gatorade

Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry  1


This experiment was carried out to determine the levels of glucose present in both coke and Gatorade by use of spectrophotometry and compare the results to find which sample had the highest concentration of glucose. The results were consistent with previous researches which show that the concentration of glucose in Coke is higher than that of Gatorade; an outcome that opposed the hypothesis. The concentration of glucose in Coke from the calculation was found to be 4.912g/100mL while the concentration in Gatorade was found to be 0.759g/100mL. The difference between the two samples was 4.153g/100mL, this difference is large as compared to previous experiments, and the difference might be as a result of errors incurred while carrying out the experiment such as varying concentration of glucose in the sample used. The experiment can be improved to provide data that is more accurate.


In human metabolism, glucose is considered a very important monosaccharide and it is the primary source of energy in human body, providing energy of approximately 2870kJ/mole. In the body, the cells gain energy from oxidation of nutrients like glucose and others (Schulze, Manson, Ludwig, Colditz, Stampfer, Willett, & Hu, 2004). Glucose in the body is oxidized through the process of aerobic and anaerobic metabolism (Pearson, 2016). The transfer of H+ electron ions by use of glyceraldehyde phosphate dehydrogenase (GPDH) to co-enzyme nicotinamide adenine dinucleotide phosphate (NADP+) during oxidation produces nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP) (Pearson, 2016).

Glucose in the blood is referred to as ‘blood sugar’; its concentration is 0.1 percent but it can change due to different condition. For example, a person suffering from diabetes has a high concentration of sugar in the body. Studies shows that the prevalence of obesity and type 2 diabetes have increased in today’s society because of increased consumption of affordable sugary drinks (Schulze et al., 2004). The consumption of beverages with high concentration of sugar, such as Coke and Gatorade, in today’s society and the increase in health problems, such as obesity and type 2 diabetes, makes it a topic interesting to study to ascertain which drinks have higher concentrations of glucose.

Enzymes are catalysts that speed up the rate of chemical reactions. They achieve this by reducing the activation energy needed for the reaction to proceed. They react with one or more substrates to produce one or more products. Some enzymes may need the presence of either co-factors or co-enzymes such as Mg2+ or NAD+/NADH, respectively, to support the reaction (Pearson, 2016). Enzymes do not have any effect on free-energy changes that are associated with the reactions they act upon. The company producing Gatorade indicates that it contains glucose and sucrose while company producing Coke indicates that it contains only sucrose. Based on this information, it can be hypothesised that Gatorade has higher concentration of sugar than Coke because Coke contains only sucrose.

It has been noted that several enzyme-catalysed reactions, followed by the use of spectrophotometry, mainly rely on the differing absorbance characteristics of oxidized and reduced NAD+/NADH or NADP+/NADPH. For example, at a wavelength of 340nm NADPH absorbs better than NADP+(Pearson, 2016). Therefore, reactions that involve the appearance and disappearance of NADPH can be monitored using a spectrophotometer. In this experiment, glucose concentration in Coke and Gatorade is determined through a reaction sequence that involves the appearance and disappearance of NADPH.

Reaction sequence:

Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry  2Source: Pearson, 2016

As indicated in the laboratory manual, samples for Coke and Gatorade, 5 glucose standards and 1 blank were prepared using the 20mM stock solution and distilled water, at dilutions of 2mM, 3mM, 4mM, 5mM and 6mM. The spectrophotometer wavelength was set at 340 nm and the initial absorbance of each sample was measured. Then, the TEA buffer was added to each sample and mixed by pipetting. After a period of 15 minutes, the absorbance was measured and the difference in absorbance was calculated.

Results and Calculations

Table 1: Table of recorded and calculated results.

A1 (0 min)

A2 (+15 min)

Absorbance difference (A2-A1)

0mM (Blank)


The results showed an increase in NADPH as glucose concentration increased. When the graph was drawn, a trend line was used to show the increasing gradient in NADPH in comparison to increasing glucose concentrations in the samples. The trend line was used to determine the glucose concentration in both Coke and Gatorade. The results showed that the concentration of glucose was higher in Coke than in Gatorade.

Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry  3

Figure 1: The concentration of Coke is 2.75mM and the concentration of Gatorade is 0.35mM.

Figure2:Calculationsfor glucose in Coke and Gatorade.

Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry  4

Lab Report: Determination of Glucose in Coke and Gatorade using Spectrophotometry  5

Discussion and conclusion

Analysis of the table and graphs showed that there was a proportional relationship between absorbance and concentration. A study by the American Journal of Undergraduate Research (2008) showed a direct proportional relationship of absorbance and concentration of glucose in a sample that was used; this confirmed the results of the experiment (Miloski, Wallace, Fenger, & Schneider, 2008).

The results from the graph did not show the linear relationship that was expected, therefore, it was deduced that the results showed inaccurate concentrations of glucose in Coke and Gatorade. This suggested that errors had occurred during the experiment, most likely from the improper zeroing of the spectrophotometer. Another source of error was seen in the blank sample. This sample had an absorbance of 0.005mM which was incorrect as absorbance should be 0mM. This suggested that the blank sample was contaminated with glucose, which may have affected the data. To improve this experiment, it is important to ensure no contamination occurs and that correct zeroing of the spectrophotometer is made. Furthermore, the pH of the beverages should be known before the experiment is conducted so that the hypothesis can be modified in accordance to provide for expected sucrose hydrolysis.

When the excel graph was used to plot and analyse the results, it was found that the glucose concentration is 2.75mM for Coke and 0.35mM for Gatorade. This was not consistent with the calculated results. The results disproved the hypothesis which stated that the concentration of glucose in Gatorade should be higher than that of Coke because Coke contains only sucrose. This can be explained by the hydrolysis of sucrose in Coke. In a pH that is higher than 7, sucrose is more stable. This indicates that as the pH of a solution becomes more acidic, the inversion of sucrose increases. This involves the hydrolysis of sucrose into fructose and glucose (Miloski, Wallace, Fenger, & Schneider, 2008). Since the pH of Coke is 2.5 and the pH of Gatorade is 2.95, this suggested that the acidic environment in both beverages promoted hydrolysis (Miloski, Wallace, Fenger, & Schneider, 2008). Therefore, it has been deduced that the acidic conditions and sucrose content of Coke cause the hydrolysis of sucrose to take place faster and in higher quantities than in Gatorade. From the experimental results,it was established that the glucose concentration ofCoke is higher than in Gatorade. This places Coke as the unhealthier beverage because high sugar content increases the chances of a person developing diabetes (Schulze et al., 2004).


Miloski, K., Wallace, K., Fenger, A & Schneider, E.(2008). Comparison of Biochemical and Chemical Digestion and Detection Methods for CarbohydratesAmerican Journal Of Undergraduate Research, 7(2), 7-18

Pearson, A. (2016). 1015MSC Chemistry of Biological Systems Laboratory Manual. Gold Coast, Griffith University.

Schulze, M., Manson, J., Ludwig, D., Colditz, G., Stampfer, M., Willett, W., & Hu, F. (2004). Sugar-Sweetened Beverages, Weight Gain, and Incidence of Type 2 Diabetes in Young and Middle-Aged Women. The Journal of The American Medical Association (JAMA), 292(8), 927

Coca-Cola. (2015). Coca-Cola; Nutritional Information. Retrieved on 10/18/16 from