Worksheet: The Chemistry of Food
In this worksheet, we will practice describing how to carry out chemical tests on food for the presence of sugars, starch, protein and fats.
A sample is tested with iodine. What is the color change that will occur if the sample contains starch?
- ABlue-black to brown
- BPale blue to purple
- CBrown to brick red
- DBrown to blue-black
- EBrown to cloudy white precipitate
Complete the table to show the correct biological molecule being tested for, or the name of the test.
|Molecule Being Tested for||Starch||2||Protein||4|
|Name of Reagent/Test||1||Ethanol/Emulsion test||3||Benedict’s solution|
- A1: Iodine, 2: Sugars, 3: Biuret, 4: Lipids
- B1: Biuret, 2: Sugars, 3: Iodine, 4: Carbohydrates
- C1: Iodine, 2: Lipids, 3: Biuret, 4: Sugars
- D1: Biuret, 2: Lipids, 3: Iodine, 4: Sugars
- E1: Biuret, 2: Sugars, 3: Iodine, 4: Lipids
A sample is tested using the emulsion test with ethanol. What will the result be if the sample contains lipids?
- AA purple solution
- BA layer of cloudy white emulsion
- CA blue-black solution
- DA brick-red precipitate
- EA pale blue solution
A banana was tested for different food groups and the results are shown below.
|Reagent Added/Test Performed||Iodine||Benedict’s||Biuret|
|Result||Blue black||Brick red||Light purple|
Which of the following is the correct conclusion about the biological molecules found in the banana?
- AThe banana contains starch, sugar, and some protein.
- BThe banana contains starch and sugar but no protein.
- CThe banana contains neither starch, sugar, nor protein.
- DThe banana contains starch but neither sugar nor protein.
Proteins are polymers. What monomers are they made from?
- AFatty acids
- DAmino acids
An egg yolk was tested for different food groups and the results are provided.
|Reagent Added/Test Performed||Iodine||Benedict’s||Biuret||Emulsion|
|Result||Orange||Blue||Purple||White emulsion layer|
According to these results, which of the following is the correct conclusion about the biological molecules found in the egg yolk?
- AThe egg yolk contains sugars and starch, but not protein.
- BThe egg yolk contains fats and proteins, but neither starch nor sugars.
- CThe egg yolk contains starch, sugars, protein, and fats.
- DThe egg yolk contains sugars and proteins, but neither starch nor fats.
Two samples of food have been tested with the emulsion test. What are the biological molecules contained in sample Y, according to the demonstrated results?
- AReducing sugars
Complete the statements to correctly describe the composition of the biological molecules.
A protein is made of many monomers called .
- Afatty acids
- Bamino acids
Many sugar molecules, like glucose, join together to form .
A basic lipid molecule is formed of one and three fatty acids.
- Damino acid
When carrying out the test for reducing sugars using Benedict’s reagent, the mixture should be heated in a water bath. Why should a water bath be used, rather than a Bunsen burner?
- AIt is too dangerous to use a Bunsen burner near Benedict’s reagent.
- BA Bunsen burner should only be used to heat up water, not other mixtures.
- CIt is easier to maintain a constant temperature when using a water bath.
- DA Bunsen burner will not reach the required to heat the mixture.
- EThis is incorrect; a Bunsen burner should be used.
Carbohydrates are polymers. What monomers are they made from?
- BAmino acids
- CSimple sugars
- DFatty acids
Benedict’s solution is used to test samples for the presence of sugars. The results from multiple tests are shown in the diagram given.
Which sample has a high proportion of reducing sugars?
- DNone of the samples
Which sample has small traces of reducing sugars?
- DNone of the samples
Two samples of food have been tested with the biuret test. What is the biological molecule contained in sample Y, according to the demonstrated results?
- AReducing sugars
A sample is tested using the biuret test. What color change will occur if protein is present in the sample?
- APale blue to purple
- BPale blue to white emulsion
- CPurple to pale blue
- DPurple to brick red
- EPale blue to brick red
A cookie was tested for different food groups and the results are shown below.
|Reagent Added/Test Performed||Iodine||Ethanol||Biuret|
|Result||Blue black||White emulsion||Blue|
Which of the following is the correct conclusion about the biological molecules found in the cookie?
- AThe cookie does not contain starch, fats, or proteins.
- BThe cookie contains starch and fats, but not protein.
- CThe cookie contains neither starch nor fats, but some protein.
- DThe cookie contains fats, but neither starch nor protein.