Question

Answer all the questions

Define each of the following terms as they relate to this experiment and give an example of each term: carbohydrate Benedict's test lipid Iodine test protein Biuret test nucleic acid Sudan IV test positive control negative control Answer the following questions in complete sentences, based on your experimental results: 1. Which is a reducing sugar, sucrose or glucose? How do you know? 2. Which contains more reducing sugars, potato juice or onion juice? How do you know? 3. Which colors more intensely in the iodine test, onion juice or potato juice? Why? 4. Which solution is a positive control in the Biuret protein test? 5. Which solution is the negative control in the Biuret protein test? 6. Which contains more protein (C-N bonds), egg albumin or honey? How can you tell? 7. Do free amino acids have peptide bonds? 8. What observation indicates a positive test for lipid? 9. Does honey contain much lipid? Explain how you know? 10. Lipids supply more than twice as many calories per gram as do carbohydrates. Based on your results, which contains more calories, oil or honey? Explain your answer.

Answer 1

Definitions:

Carbohydrate-- Organic compounds formed of C,H,O where for every C atom has one H2O molecule is present and they are important for energy.

Lipid--Organic compounds formed of C,H,O and concentrate sources of energy and hydrophobic in nature.

Proteins--Organic compounds with C,H,O and N, which are very important for various metabolic activities and polymers of amino acids.

Nucleic acids--Nitrogenous , organic compounds and polymers of nucleotides which store genetic information and express it in the cells.

Positive control--In a scientific experiment, positive control is a group that receives a treatment with known results and is expected to show a change in the experiment.

Negative control--In a scientific experiment, a negative control is a group which does not receive the experimental treatment and is not expected to show the result.

Benedict's test--A test to detect the presence of reducing sugars in the given sample by producing an organge to red precipitate.

Iodine test--A test to detect the presence of starch where blue black color is obtained with Iodine if starch is present in the substance.

Biuret test--A chemical test used to detect the presence of peptide bonds.

Sudan IV test-- Sudan IV is a fat soluble dye, which stains lipids present in the substance.

Answers :

1. Glucose is a reducing sugar. This is because glucose gives orange precipitate with Benedict's solution.

A reducing sugar is the one which has an aldehyde group or ketone group.

2. Onion juice contains more reducing sugars because it gives a positive test with Benedict's reagent.

3. Potato juice gives more intense color with starch because , potato has starch. Starch gives blue black color with Iodine.

4. Any protein extract is a positive control in a Biuret test.

5. The substance is not added with reagent in negative control. Which ever tube does not have the reagent is negative control.

6. Egg albumin contains more C-N bonds as it is rich in proteins. Honey is a carbohydrate. Proteins give post to Biuret test.

7. Free amino acids do not have peptide bonds. The bonds are formed only when the amino acids are linked to form proteins.

8. A positive test for lipids is with Sudan IV. Sudan IV will stain the lipid reddish orange.

9. Honey is rich in sugars. It does not contain much lipid. This we can know by testing it with Sudan IV.

10. Oil contains more calories. This is because, oil is lipid and it produces more than double the amount of energy when we compare with carbohydrate , which is honey in this case.