Student Exploration: Identifying Nutrients Answers

1. Test: Under the Benedict test, click Test. Does sample A contain monosaccharides?

Yes

Does Sample A contain monosaccharides?

Yes

3. Test: The Biuret test uses a solution of potassium hydroxide (KOH) and copper sulfate (CuSO4) to test for protein. The Biuret solution turns purple when proteins are present. Under Biuret test, click Test. Does sample A contain proteins?

No

4. Test: The Sudan Red test uses a fat-soluble dye, Sudan Red, to indicate the presence of lipids. When lipids are present, the dye will be absorbed into the lipids, and will appear as concentrated spots of color in the test tube. (No spots indicates that lipids are not present.) Under Sudan Red test, click Test. Does sample A contain lipids?

No

5. Think and discuss: If possible, discuss these food samples with your classmates and teacher. Try to come up with a type of food that corresponds to each sample.

In general, meats are rich in proteins and lipids. Fruits and products flavored with corn syrup contain monosaccharides. Grain and potato products contain starch. Samples that are negative for every test are likely to contain disaccharides such as table sugar.

C. Is sample M most likely to be chicken, rice, a mango, or butter? Justify your answer.

Rice. Sample M has starch, which is found in rice. Chicken is rich in protein, mangoes in monosaccharides, and butter in lipids.

5. Summarize: What nutrients does sample A contain?

Sample A contains monosaccharides.

1. Below the Food samples label, drag tube A into the Food sample holder. Below the Benedict test, click the Test button. What is done in the Benedict test?

The food sample and Benedict solution are added to a test tube. The tube is heated in a water bath for five minutes.

6. Analyze: What kind of food is sample A most likely to be?

A. Apple juice

6. Extend your thinking: In general, a balanced diet contains relatively even amounts of carbohydrates, proteins, and lipids. Too much sugar (monosaccharides and other simple sugars) is unhealthy. Fruits and vegetables are important sources of vitamins and minerals. Do you consider your diet balanced and healthy? Why or why not?

Answers will vary. Sample answer: My diet is healthy because it contains a balance of starch, proteins, and lipids. I also eat a lot of fruits and vegetables. [Unhealthy diets may be high in sugar, fats, carbohydrates, and processed foods.]

3. Draw conclusions: Why is it important to understand the nutritional content of food?

Answers will vary. Sample answer: What we eat is important to our health. A healthy diet is low in sugar and contains a balance of carbohydrates, proteins, and fat. To have a healthy diet, it is important to learn about the nutritional contents of different types of food.

1. What are the major types of nutrients you can get from food?

Answers will vary. [Major nutrients include proteins, fats, carbohydrates, vitamins, and minerals.]

2. How are these nutrients used by your body?

Answers will vary. [Proteins are used to build body structures such as muscle. Fats are used for cells, insulation, and energy. Carbohydrates are used for energy. Vitamins and minerals have a variety of functions.]

4. Practice: Determine the nutritional content of the remaining food samples.

B, -, -, +, +, No, No, Yes, Yes C, -, +, -, -, No, Yes, No, No D, -, -, +, +, No, No, Yes, Yes F, -, -, -, -, No, No, No, No H, -, -, +, +, No, No, Yes, Yes I, +, -, -, -, Yes, No, No, No J, -, -, +, +, No, No, Yes, Yes K, +, -, -, -, Yes, No, No, No L, -, -, +, +, No, No, Yes, Yes N, -, +, -, -, No, Yes, No, No O, -, -, -, -, No, No, No, No P, +, -, -, -, Yes, No, No, No Q, -, -, +, +, No, No, Yes, Yes R, -, +, -, -, No, Yes, No, No S, -, -, +, +, No, No, Yes, Yes,

1. Collect data: Use the four available tests to find the nutritional content of samples E, G, and M. (Sample A has been done for you as an example.) Record results on the table below.

E, -, -, +, +, no, no, yes, yes G, -, -, -, -, no, no, no, no M, -, +, -, -, no, yes, no, no

2. Test: The Lugol test uses iodine to test for starch, a polysaccharide (complex sugar). Iodine turns dark purple in the presence of starch. Under Lugol test, click Test. Does sample A contain starch?

No

A. Is sample E most likely to be steak, bread, or butter? Justify your answer.

Steak. Sample E has protein and fat. Of the choices, only steak has protein and fat

B. Is sample G most likely to be table sugar, pasta, or olive oil? Justify your answer.

Table sugar. Sample G has no monosaccharides, but it may have disaccharides like sucrose. Pasta would be positive for starch, and olive oil contains lipids.