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Question Video: Matching Each Biological Molecule with the Correct Test or Reagent That Is Used to Detect the Presence of That Molecule in a Sample Biology

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


Video Transcript

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

Key knowledge required to complete this table is knowing the appropriate food test for each type of biological molecule, sometimes also called biological macromolecules. The table contains the names of two biological molecules, starch and protein, and also the names of two food tests, the ethanol/emulsion test and also a test that uses Benedict’s solution as a reagent. Let’s review three biological molecules common in both our food and our bodies, carbohydrates, lipids, and proteins, as we determine how we should fill out this table.

These biological molecules are polymers, which means they’re made out of many repeating similar units. And those units are called monomers. The monomers that bond together to form larger carbohydrates are called sugars, but sugars can be standalone carbohydrates by themselves as well. The monomers of lipids that we’ll consider here are the glycerol and fatty acids found in fats, which are a type of lipid. And the monomer units that bond together to form proteins are called amino acids. Some examples of carbohydrates include glucose and lactose, which are both simple sugars, and also some larger carbohydrates, such as starch or glycogen. And fats can also be divided into whether they’re saturated fats or unsaturated fats. A couple examples of proteins include myosin and actin, which are in our muscle cells and allow us to move.

Next, we’ll list the tests used to identify these biological molecules in food samples. In carbohydrates, there’re two different tests for two different kinds of carbohydrates, both the reducing sugars, which include all the simple sugars, and starches. The test for sugars is a test that requires a solution called Benedict’s solution. And once the Benedict solution is added to the food sample, it has to sit in a warm water bath for a few minutes. The test that’s used for starches, which is again many glucose molecules bonded together, is the iodine test. And an iodine solution is simply applied to the food sample. The food test for lipids uses ethanol, and it looks to see if the food sample will form an emulsion, which is cloudy. And the test used to identify protein in a food sample is called Biuret test.

And we’re ready to start filling in our table. To identify starch in a food sample, we need to use the iodine test. And the reason for adding ethanol to a food sample to see if an emulsion will form is if you’re checking for lipids. And when we wanna look for protein in a sample, we wanna use a Biuret test. If you leave a food sample in a warm water bath with Benedict’s solution, that would be a test for sugars.

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