What subunits (small molecules) make up: a. Carbohydrates b. Proteins What is th

Question

What subunits (small molecules) make up: a. Carbohydrates b. Proteins What is the purpose of using a positive and a negative control for each test? Why might a substance taste sweet, yet produce a negative reaction using the Benedict's test? What procedure could you use to check your answer to the previous question? You have tested a sample with Biuret and Benedict's reagents. The solution mixed with biuret blue. The solution boiled with Benedict's reagent is also blue. What does this tell you about the Since potatoes have starch in them, why don't they taste sweet after they are boiled?

Explanation / Answer

1 a. Carbohydrates are made up of smaller units called monosaccharides. Monosaccharides consist of carbon, hydrogen and oxygen in the ration 1:2:1. Examples of monosaccharides include glucose,galactose and fructose.

1b. Proteins are made up of amino acids.Amino acids have two functional groups; a carboxyl group and an amino group.

2. A positive control is one in which a known response is expected. A negative control is one in which there is no response expected.Positive and negative controls are used to compare the test results.The purpose of positive control is to bring about a positive result.It brings about a change in the value of dependent variable.The negative control is supposed to not show any change in the dependent variable.

3. Benedicts test is used to detect the presence of reducing sugars.But a substance can taste sweet due to the presence of artificial sweetners or sucrose, both of which are not reducing sugars, therefeore benedicts test is negative .

4. Iodine reagent can be used .

5. Biuret test is test for the detection of proteins .Blue colur indicates absence of proteins.In case of Benedicts test, blue colour indicates the absence of reducing sugars. It means the solution does not contain reducing sugars and proteins.

6. boiling does not hydrolyse starch so that it can release glucose.The glucose units in starch are linked up in chains and boiling potatoes does not break these chains.

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