Question 5 High fructose corn syrup (HFCS) is a sweetening agent used in the foo

Question

Question 5 High fructose corn syrup (HFCS) is a sweetening agent used in the food industry. HFCS is made enzymatically from cornstarch. Starch is first converted to short oligosaccharides and then to glucose monomers. Then an isomerase is used to convert glucose to fructose, and the resulting product is an approximately 50/50 mixture of glucose and fructose. Why bother? Why is glucose converted to fructose, rather than simply being used directly as a sweetener? (a) (b) Why is HFCS a 50/50 mixture? Why is it not possible to convert more of the glucose to fructose? In liver, fructose is metabolized by the pathway shown below. If glyceraldehyde-3 phosphate is converted to pyruvate by the reactions of glycolysis, what is the net ATP yield per molecule of fructose? [For interest: mutations in the gene encoding aldolase B cause hereditary fructose intolerance, which requires dietary exclusion of fructose]. (c)

Explanation / Answer

a)

The relative Sweetness factor of fructose is 110, whereas glucose or dextrose has 74. So, fructose is used as a chief sweetening agent in food sources. If we use glucose as a sweetening agent, then it will steeply increase the blood glucose level and cayuses several disorders, like diabetes but, fructose does not        

b)

Here, the enzyme which converts Glucose to fructose is called Phosphoglucoisomerase, it a reversible enzyme, if the fructose levels increases in the reaction mixture, then it will inhibit the enzyme in a non-competitive of feedback manner. So, this enzyme has Keq is 0.31 for both experimental and Haldane constant.

c)

The net ATP yield per molecule of fructose is: 6 ATP.

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