BIOL130L Final: Final Exam Review 11 pages of notes including results from each experiment, expected results, an overview of the procedure and theory as well as charts, diagrams and pictures

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cerisemole687

16 Oct 2011

School

University of Waterloo

Department

Biology

Course

BIOL130L

Professor

Dragana Miskovic

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Document Summary

Iodine test turns blue-black in the presence of starch and reddish brown in the presence of glycogen. Starch and glycogen only differ in their overall shape and degree of branching, Starch is a mixture of amylose and amylopectin its the reaction of amylose and iodine that gives the blue colour. The reaction of iodine and the highly branched components of glycogen gives it a reddish brown colour. Aldehyde group that reacts with benedicts solution to indicate the presence of a reducing sugar. A positive test ranges from yellow, green, red or brown. Benedicts solution contains blue cupric ions (cu++ dissolved in naoh) The aldehyde groups will reduce it to cuprous ions (cu+) and combine with oxygen to form a precipitate of cu2o. 4 cu+ + 2oh- +2e 2cu2o + 2h+ + 2e. The amount of cuprous oxide formed is proportional to the concentration of free aldehyde groups in the solution.

Related Questions

Benedicts Test for Reducing Sugars:

Tube Solution/food Color reaction to Benedicts solution Presence ofreducing sugar (green/reddish orange color)
1 1ml distilled water
2 good pinch glucose powder
3 good pinch table sugar (sucrose)
4 2 drops honey
5 finely chopped onion
6 finely chopped fruit
7 1ml milk
8
9
10

Which of the above solutions was included as your negative control?[1 pt]

Which of the above solutions was included as your positive control?[1 pt]

Which of the above foods/solutions tested positive for sugars? [4pts]

Explain why sucrose (table sugar) yielded the result above. [2pts]

What does this tell you about the way sugars are stored, forexample in onions? [2 pts]

Sugar is actually a common name for glucose. Glucose is stored asstarch in onions as it is a bulb present in plants.

Would you use the Benedicts test to investigate if a cake mix weresugar free? Explain your answer [2 pts]

The benedicts test cannot be used to determine if a cake mix issugar free or not. This is because benedicts test is used todetermine the presence of reducing sugars like maltose and lactose.Fructose also gives a positive test. We use sucrose in food so wecannot detect the presence or absence of sucrose in the cakemix

Iodine Test for Starch:

Depression Number Solution/food Color reaction to iodine solutionPresence of starch (bluish-black color)
1 Â½ ml distilled water
2 pinch glucose powder
3 pinch cornstarch
4 Â½ ml egg white
5 finely chopped onion
6 Finely chopped potato
7 1 drop honey
8
9
10

Which of the above solutions was included as your negative control?[1 pt]

Which of the above solutions was included as your positive control?[1 pt]

Which of the above foods/solutions tested positive for starch? [4pts]

Did any of the animal sources contain starch? Explain your answer.[2 pts]

Did any of the same foods test positive for both reducing sugars(Benedicts Test) and starch (Iodine Test)? Explain your answer. [4pts]

Proteins:
Tube Solution/food Color reaction to Biuret Reagent Presence ofprotein (violet color)
1 2ml distilled water
2 2ml milk
3 2ml egg white
4 2ml egg yolk
5 2ml honey
6
7
8
9
10

Which of the above foods/solutions tested positive for protein? [4pts]

Did any of the foods/solutions that tested positive for proteinalso test positive for reducing sugars (Benedicts Test) or starch(Iodine test)? Explain your answer. [2 pts]

How is the structure of proteins in plants and animals similar? [3pts]

How are proteins in plants and animals different? [3 pts]

Lipids:

Test Solution/food Grease spot indicating the presence oflipid
1 1ml distilled water
2 Oil-vinegar salad dressing
3 walnut
4 Egg white (wipe away excess)
5 Egg yolk (wipe away excess)
6
7
8
9
10

Which of the foods tested were positive for the presence of lipid?[4 pts]

Part 2 â Tracking Macromolecules in Your Diet

Include a copy of your ânutrient intakeâ and record the followingnutrient intakes in the space below. NOTE: Nutrient Intake is thename of the report generated at www.MyPyramid.gov [10 pts]

Kilocalories Percent Total Recommended
Energy Intake Intake

Carbohydrate ___________ ______________ 45-65%

Protein ________________ ______________ 10-35%

Total Fat _______________ _______________ 20-35%

Show your calculations in the space below

How did your consumption of macronutrients compare to therecommended intake?

orangehippopotamus244

You will use two tests in your experiment:

1. I 2 KI test for presence of starch. When I 2 KI is added to the unknown solution, the solution turns purple or black if starch is present. If no starch is present, the solution remains a pale yellow-amber color.

2 . Benedictâs test for reducing sugar. When Benedictâs reagent is added to the unknown solution and the solution is heated, the solution turns green, orange, or orange-red if a reducing sugar is present (the color indicates the sugar concentration). If no reducing sugar is present, the solution remains the color of Benedictâs reagent (blue).

---

Hypothesis Hypothesize about the selective permeability of dialysis tubing to the substances being tested.

... ?

Prediction Predict the results of the I 2 KI and Benedictâs tests based on your hypothesis (if/then).

....?

Experiment 1: Testing for Proteins

Data Tables

Table 1: Testing for Proteins Results

Sample	Initial Color	Final Color	Is Protein Present?
1. Albumin Solution
2. Gelatin Solution
3. Glucose
4. Water
5. Unknown

Post-Lab Questions

Record your hypothesis about what will happen when Biuret solution is mixed with the solutions from test tubes 1, 2, 3, and 4 here. Be sure to use scientific reasoning to support your hypothesis.

Write a statement to explain the molecular composition of the unknown solution based on the results obtained during testing with the Biuret solution and each sample solution.

Diet and nutrition are closely linked to the study of biomolecules. How should you monitor your food intake to ensure the cells in your body have the materials necessary to function?

There are other types of reagents used to determine what type of biomolecule a substance is. For example, copper ions present in Benedictâs reagent reacts with the free end of any reducing sugars, such as glucose, when heated. Originally blue in color, these copper ions are reduced by the sugar, and produce an orange-red colored precipitate. Alternatively, iodine-potassium iodide (IKI) may also be used when working with starch. IKI contains special tri-iodine ions which interact with the coiled structure of a starch polymer. Prior to a reaction, the IKI displays a yellow-brown color; however, after reacting with starch, a dark purple or black color is presented.

The molecule pictured below produced a blue color when tested with Benedictâs reagent, a yellow color when tested with IKI, and a violet color when tested with Biuret reagent. Based on the structure shown below and these chemical results, what kind of biomolecule is this?

BIOL130L Final: Final Exam Review 11 pages of notes including results from each experiment, expected results, an overview of the procedure and theory as well as charts, diagrams and pictures

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