PART 2 Geometry of Carbohydrates
- Instuctions
- Carbohydrate Material to Include:
- Pictures from the geometry exercise with explanations as to what is displayed in the picture.
- Carbohydrate Lab:
- Summary of Results - what did you see for the unknown samples and the food samples?
- Were any of the results for the food sample surprising?
Geometry of Carbohydrates
Above, a water molecule is gown. It is made up of 2 Hydrogen molecules and 1 oxygen molecule. Water, interestingly, is formed, along with carbon dioxide (CO2), during the creation of disaccharides such as lactose.
Above is a glucose molecule. Glucose is the carbohydrate that is most essential for the body to function. It is composed of 6 carbon atoms, 6 oxygen atoms and 12 hydrogen molecules. It has the formula C6O6H12.
Above is a galactose molecule. Galactose is made up of 5 carbon atoms, 5 oxygen atoms and 10 hydrogen atoms. It has the formula C5O5H10.
Above is a fructose molecule. Fructose has a different structure than glucose but has the exact same formula. This means that fructose and glucose are isomers. Fructose has 6 carbon atoms, 6 oxygen atoms and 12 hydrogen atoms. It has the formula C6O6H12.
Above is a picture of glucose and fructose combined.
Above is a picture of starch. Starch is made up of 4 glucose molecules.
Carbohydrates Lab
(Introduction to Carbohydrates)
Summary of Results
(below) Data Table 1- Unknown substance Identity tests
(below) Data Table 1- Unknown substance Identity tests
(below) Data Table 2- Food Identity tests
Post Lab Questions and Answers
- Maltose and Lactose are both disaccharides made up of 2 glucose molecules. Because their structures are so similar, both molecules have the exact same numbers of each type of element and both molecules are disaccharides, it would be impossible to distinguish the two.
- Sucrose is made up of fructose and glucose. Because Seliwanoff’s reagent break up the sucrose into its two parts, the glucose portion of it could react with the reagent and give a false positive test result.
- Benedict’s test is not a good method to determine if somebody is a diabetic because the test only checks if glucose is present in the sample, not how much glucose is present in the sample. If it was assumed that everyone with glucose in their blood was a diabetic then everyone would appear to be a diabetic because everyone has to have glucose in their bloodstream in order to survive. Benedict’s test is a very ineffective test to determine who is a diabetic.
- Fructose is sweeter than sucrose, aka table sugar. Fructose has a more concentrated sweetness and is easier to obtain, making it a cheaper, more effective sweetener.
What did you see for the unknown samples and the food samples?
We were able to identify all of the unknown samples by conducting all 4 tests. We found that the blank test tube was filled with water because it reacted negatively to each test. We discovered that test tube A contained Lactose because it gave negative results for each test. We found that test tube B was filled with Fructose. We found that test tube C was filled with sucrose because it gave negative results on Benedict's test. We discovered that test tube D was filled with Starch because it gee positive results for the iodine test. Finally, we found that test tube E was filled with glucose because it gave negative results on Seliwanoff's test.
We were also able to identify some of the carbohydrates in each of the 4 foods that we were given. We found that chocolate contained sucrose as well as monosaccharides. We were unable to determine whether the monosaccharides present were glucose or fructose molecules because the class ran out of Seliwanoff's reagent before we started our tests. We found that honey contains disaccharides. Because honey passed Benedict's test and failed Barfoed's test we must conclude that honey contains Lactose. We found that breadcrumbs contain starch and monosaccharides. We predict that it contains glucose and not fructose because breadcrumbs are not fruits. Finally, we found that milk contains Lactose and monosaccharides. Once again we predict that it contains glucose and not fructose because milk is not a fruit.
Were any of the results for the food sample surprising?
All the results expected except for the result for Honey. It was strange to find that honey contained Lactose. We reasoned that the most probable reason for this is that Honey is made by bees, the same way that milk is made by cows. The process by which bees turn pollen into honey must create lactose along the way. It is possible that many animal as well as bug products contain lactose.