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Lesson Worksheet: The Chemistry of Food Biology

In this worksheet, we will practice describing how to carry out chemical tests on food to determine the presence of sugars, starch, protein, and fats.

Q1:

A sample is tested with iodine. What is the color change that will occur if the sample contains starch?

  • AFrom blue-black to brown color
  • BFrom pale-blue to purple color
  • CFrom brown to brick red
  • DFrom brown to blue-black color
  • EFrom brown to cloudy white precipitate

Q2:

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

Q3:

Complete the table to show the correct biological molecule being tested for, or the name of the test.

Molecule Being Tested for Starch2Protein4
Name of Reagent/Test1Ethanol/Emulsion test 3Benedict’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

Q4:

Proteins are polymers. What monomers are they made from?

  • AFatty acids
  • BGlycerol
  • CSugars
  • DAmino acids

Q5:

A banana was tested for different food groups and the results are shown below.

Reagent Added/Test PerformedIodineBenedict’sBiuret
ResultBlue blackBrick redLight 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.

Q6:

Complete the statements to correctly describe the composition of the biological molecules.

A protein is made of many monomers called .

  • Afatty acids
  • Bamino acids
  • Cglycerols
  • Dsugars

Many sugar molecules, like glucose, join together to form .

  • Aproteins
  • Bcarbohydrates
  • Clipids

A basic lipid molecule is formed of one and three fatty acids.

  • Aglycogen
  • Bglucose
  • Cglycerol
  • Damino acid

Q7:

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
  • BProtein
  • CLipids
  • DStarch

Q8:

An egg yolk was tested for different food groups and the results are provided.

Reagent Added/Test PerformedIodineBenedict’sBiuretEmulsion
ResultOrangeBluePurpleWhite 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.

Q9:

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 75C to heat the mixture.
  • EThis is incorrect; a Bunsen burner should be used.

Q10:

Carbohydrates are polymers. What monomers are they made from?

  • AGlycerol
  • BAmino acids
  • CSimple sugars
  • DFatty acids

This lesson includes 24 additional questions for subscribers.

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