Chem 131 Carbohydrates Lab

Good Essays
D_____ J_____ CARBOHYDRATES LAB
May 22, 2013

Pre-lab Questions

1. The water in test tube No. 1 is a negative control. No reaction is expected to occur because water is not a carbohydrate. Reaction by a negative control is evidence of contamination.

2. The color changes expected for positive test results are Benedict’s test: orange to brick red Tollen’s test: metallic silver Starch iodine test: blue-black

3. Identify each of the samples in Part 1 as monosaccharide, disaccharide or polysaccharide.

Water = not a saccharide Glucose = monosaccharide Fructose = monosaccharide Galactose = monosaccharide Sucrose = disaccharide Lactose = disaccharide Starch = polysaccharide Honey = primarily monosaccharides with some disaccharide Saccharine = not a saccharide Nutrasweet = not a saccharide

Part 1: Benedict’s Test
Procedure

Place ten drops of 1% solution of carbohydrate and ten drops of water in individual test tubes. Add 2 mL of Benedict’s reactant and place tubs in hot water bath of 200 mL water in a 400 mL beaker for t0 minutes. Record observations.

Results

BENEDICT’S TEST TUBE | SOLUTION | OBSERVATION | 1 | Water | Clear light blue | 2 | Glucose | Opaque brick red | 3 | Fructose | Opaque orange-red | 4 | Galactose | Opaque brick red | 5 | Sucrose | Clear light blue | 6 | Lactose | Clear dark blue w/ thin red-brown layer on top | 7 | Starch | Cloudy orangish-yellow | 8 | Honey | Opaque brick red | 9 | Saccharin | Clear light blue | 10 | Nutrasweet | Clear light blue |

Discussion

Saccharides that show a positive result in this test do so because there is an anomeric carbon available in the cyclic form of the molecule which allows it to open into a straight-chain form containing an aldehyde group. The aldehyde in the straight-chain reacts with the copper ions in the reagent to produce the color change.

Positive Results. Glucose, galactose and honey all contain aldehyde

You May Also Find These Documents Helpful

  • Good Essays

    Macromolecules of Life

    • 671 Words
    • 4 Pages

    To add Benedict’s reagent to four substances, glucose, starch, onion juice, and distilled water, to test the detection of sugar in each.…

    • 671 Words
    • 4 Pages
    Good Essays
  • Good Essays

    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. 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.…

    • 1028 Words
    • 5 Pages
    Good Essays
  • Powerful Essays

    Testing for Macromolecules

    • 1267 Words
    • 5 Pages

    4. The samples connected by another group with 5 drops of Benedict's solution added were heated all together in hot water bath.…

    • 1267 Words
    • 5 Pages
    Powerful Essays
  • Satisfactory Essays

    In this lab there are I complete two different tests. The procedure was relatively the same for each test. I would first add 3ml of a given substance to a test tube, followed by 5 drops of either Biuret Reagent or Iodine. Once the agent is added, I swirled the two substances and then observed the results. The first was to test proteins, and the second, was to test starches.…

    • 419 Words
    • 3 Pages
    Satisfactory Essays
  • Satisfactory Essays

    The positive test for glucose is be adding Benedict’s solution. In the experiment, the glucose solution had the most dramatic reaction with the Benedict’s solution after it got heated. It turned to an opaque yellowish orange solution with dark-orange precipitate at the bottom while other samples all turned to a colour related to blue, other than the unknown solution.…

    • 466 Words
    • 2 Pages
    Satisfactory Essays
  • Good Essays

    Osmosis

    • 880 Words
    • 4 Pages

    The solution inside the sausage casing containing glucose and starch was transparent (clear) in the beginning of the experiment. After 30 min of incubation time the solution inside sausage casing was still transparent (clear). In IKI test, the content of sausage casing has changed color from yellow to dark purple (cuvette SI), in Benedict’s test the solution from the sausage casing changed color form clear to blue after addition of Benedict’s reagent (cuvette S), after heating solution in water bath (60°C), the content of cuvette S has changed color to yellow/orange.…

    • 880 Words
    • 4 Pages
    Good Essays
  • Good Essays

    Response | |1 |3.86 |-0.0140 |-0.0512 |-0.198 |- |0.0240 |0.00704 |0.0272 |- | |2 |7.72 |0.0210 |0.0768 |0.296 |- |0.0370 |0.0109 |0.0421 |- | |3 |11.6 |0.0610 |0.223 |0.861 |- |0.0300 |0.00880 |0.0340 |- | |4 |15.4 |0.0280 |0.102 |0.394 |- |0.314 |0.0921 |0.356 |+ | |5 |19.3 |-0.0610 |-0.223 |-0.861 |- |0.0800 |0.0235 |0.0907 |- | |6 |23.2 |0.0470 |0.172 |0.664 |+ |0.0480 |0.0141 |0.0544 |- | |7 |27.0 |0.459 |1.68 |6.48 |+ |0.000 |0.000 |0.000 |- | |8 |30.9 |0.727 |2.66 |10.3 |+ |0.0240 |0.00704 |0.0272 |- | |9…

    • 1380 Words
    • 6 Pages
    Good Essays
  • Good Essays

    The water was tested for each initial chemical test because it served as the controlled variable. Since water is pure oxygen and hydrogen unlike Glucose and Starch, one variable may be observed.…

    • 588 Words
    • 3 Pages
    Good Essays
  • Satisfactory Essays

    Physioex 12 Answers

    • 825 Words
    • 4 Pages

    A negative results with a positive control indicates a “false negative” and your results are invalidated.…

    • 825 Words
    • 4 Pages
    Satisfactory Essays
  • Good Essays

    Chemical Changes Lab

    • 730 Words
    • 3 Pages

    Procedure: In this experiment I used a 96-well plate to hold each of the chemical reactions that occurred during this lab. Using a pipet, I added two drops of one chemical with two drops of another chemical and observed the effects of each reaction.…

    • 730 Words
    • 3 Pages
    Good Essays
  • Satisfactory Essays

    1 M Sucrose Lab

    • 561 Words
    • 3 Pages

    We then went to see if the sucrose entered the bag unfortunately the benedict's solution showed negative results. The second test ( Bag: 5% ovalbumin Beaker: 1 M sucrose) we put biuret in a test tube with the beaker solution and the indicator showed negative results. Then for the next test (Bag: 1 M Glucose Beaker: distilled H2O) they put Benedict's solution in a test tube with the beaker liquid. The benedicts showed positive results. The next test (Bag 1 M Sucrose Beaker: 1 M NaCl) they put Benedict's solution in a test tube with the beaker liquid. The indicator showed negative results. For the next test(Bag: 1 M NaCl Beaker: distilled H2O) they put silver nitrate in a test tube with the beaker liquid. The silver nitrate showed positive results. The next test (Bag 1 M sucrose Beaker: 5% ovalbumin) they used mass change to determine if the solute could pass through the bag. They weighed the bag before and after. The mass of the bag decreased showing that the H2O passed through the bag. The next test (Bag: 1 M NaCl Beaker: 1 M glucose) they put silver nitrate in a test tube with the eaker liquid. The indicator tested positive. The next test( Bag 1 M Glucose Beaker 1 M sucrose) they put iodine in a test tube with the beaker liquid. The indicator showed positive results. The next and final test (Bag: 1 M glucose Beaker: 5% ovalbumin)…

    • 561 Words
    • 3 Pages
    Satisfactory Essays
  • Powerful Essays

    The use of positive and negative controls to determine the macromolecules present in an unknown solution…

    • 1307 Words
    • 11 Pages
    Powerful Essays
  • Better Essays

    review sheet 12 a&p

    • 541 Words
    • 3 Pages

    Negative result with a positive control is a false negative so the results are not true.…

    • 541 Words
    • 3 Pages
    Better Essays
  • Good Essays

    By observing the table above, we could see that Benedict's test was for reducing sugars, iodine test was for the presence of starch, filter paper was for the presence of fatty acids, and the Biuret test was for amino groups present in proteins. Benedict's solution was used to test for the presence of simple sugars, such as glucose (monosaccharide). When heated, the solution mixed with monosaccharides produced a reddish-orange colour. This was because Benedict's solution is composed of sodium citrate, sodium carbonate, and cupric sulfate pentahydrate. When solution is heated, an oxidation-reduction reaction occurs: cupric ion (Cu+2) oxidizes into a cuprous ion (C+) and precipitates into cuprous oxide (Cu2O) because Benedict's solution loses an oxygen (Cu+2…

    • 600 Words
    • 3 Pages
    Good Essays
  • Good Essays

    Nutriton lab

    • 851 Words
    • 3 Pages

    2. The purpose of testing the four test tubes was to ensure that the colour change that occurred in the substance was due to a chemical change and not the substance being added to it.…

    • 851 Words
    • 3 Pages
    Good Essays