Pre-lab: Identifying Carbohydrates

5 May 2016

There were many ranges of color changes in the Benedicts test and Iodine stain. For the Benedicts test, this oxidation/reduction response changes the arrangement of the reducing sugar creating a colored precipitate.

Pre-lab: Identifying Carbohydrates Essay Example

The change in color is correlated to the first concentration of the reducing sugar. For the iodine test, the three dimensional structure of various polysaccharides permits them to react with the iodine stain to produce a certain color.

As far as the molecular level, there is an OIL – RIG method. Oxidation occurs when a substance gains oxygen or loses electrons or hydrogen (OIL – oxidation is loss) and reduction occurs when a substance loses oxygen or gains electrons or hydrogen (RIG – reduction is gain).

Also, the distilled water (test tube one) served as a control for the experiment. Since polysaccharides are complex, the 3- dimensional sugars are often known as “complex carbs”. These molecules are composed of many elements of glucose linked together by the dehydration synthesis.

There were methods of determining whether a substance contained reducing sugars or polysaccharides. For the Benedicts test, the color changes of bluish green/greenish blue (trace amount +; honey solution, cornstarch solution, sweet ‘N’ low, sweet potato and egg yolk), green (++), yellow (+++) and orange red/rust (large amount +++: glucose/dextrose and equal) appeared, the concentration of reducing sugar indicated a positive test.

Although, when the appearance did not change and remained the color of the Benedicts’ reagent of blue, indicated no reducing sugars, or a negative (-) test (water, table sugar solution, gelatin, egg white solution, and unknown (A3) solution).

As for the Iodine stain, the color changes of bluish black (indicated plant starch; cornstarch solution and unknown A3), dark reddish brown (indicated glycogen), and violet brown to reddish brown (indicated cellulose; potato solution and sweet potato) presented positive test results for the different types of polysaccharides present.

Although, the color of yellow/amber (water, glucose/dextrose, table sugar solution, honey solution, cornstarch solution, sweet ‘N’ low, equal, gelatin, egg white solution, and egg yolk) specified no polysaccharides present. The hypothesis made for the outcome of the problem was neutrally correct.

The assumption taken was that all form of sugars would have a present amount of reduced sugars while non-sugars did not for the Benedicts test. Such as, table sugar solution and gelatin did not have reduced sugars which has no form of glucose or fructose because it is processed sugars. For the iodine test, most of the educated guesses were wrong. The results turned out to have majority tests as negative or absent presence or polysaccharides.

Analysis: Lab 2 Identifying Proteins and Lipids The Biuret solution is a blue liquid that changes to purple when proteins are present. Proteins are complex, specialized molecules composed of carbon, oxygen, hydrogen and nitrogen.

The different amino acids are similar in structure which are at the center of the molecule that is alpha carbon connected to an amino group, a carboxyl group, and a hydrogen atom with the R group. Water tested pale blue, or negative, due to being the control of the experiment; as well as the unknown A3, buttermilk (all lipids), table sugar (processed sugar) and honey (all sugars).

The following had a color change of pale violet-medium violet of low-medium concentration of protein: gelatin, chicken stock, whole milk, beef stock, egg white, skim milk, 2% milk, and soy milk. The strongest presence of protein appeared in egg yolk which is made up of 45% protein. The Sudan red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and the location of lipids in each tested solution. Lipids consist of glycerol and fatty acids “tails”.

The fatty acid “tails” are long chains of carbon and hydrogen that contribute to the non-polar behavior of fats, meaning, they don’t mix adequately with (polar) water. The fatty acid chains can be carbon saturated with hydrogen atoms forming a straight chain without double bonds.

Therefore, this is where all solutions are extracted in ethyl alcohol or as the control in the experiment. The following tested for low concentration (pale color) of lipids: wheat flour, white flour, soy flour, egg yolk and the unknown A3.

This is because these certain breads with flour have a high content of protein which lowers the content of carbohydrates, therefore has a low lipid value. Soy flour and egg yolk, especially, have the highest protein. Solutions such as cream, honey, margarine, salad oil, skim milk, coconut milk, 2% milk, whole milk, soy milk and butter varied from medium to high (strong) amounts of lipids present. Ethyl alcohol and egg white had none present.

The hypothesis made for the outcome of the problem was mostly correct. The assumption taken was that whole milk would have a strong volume of protein. Instead, there was a low concentration that was resulted for the Biurets test.

For the Sudan III test, the hypothesis was all guessed correctly due to the common sense of variations of how protein holds for each solution. It is more like a general way of finding because most of these substances can be eaten daily and at least seen on nutritional facts which came to understanding of the hypothesis.

Analysis: Lab 3 Identifying Unknown As a result of using the unknown (labeled A3) solution in all of the conducted experiments, it has come to specifically determining the identity of the unknown substance out of the list that was given, which is predicted to be table sugar solution.

This was predicted by comparing the fact that in the Benedicts test it had resulted that it was negative for reduced sugars. For the iodine test, it was resulted positive with a color change of bluish black that indicates it is a plant starch (amylose) type of polysaccharide; consisting of 74.0% carbohydrates. For the Biuret test, it resulted negative for proteins, which table sugar has 0%.

Lastly, the sudan III test resulted a low concentration of lipids which technically, table sugar does not contain. This part of the test became a bit skeptical to figure out exactly what the unknown solution is. Yet after much configuration, it seemed to be that sugar can turn into lipids at some process.

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