Data Table:

Substance / Monosaccharide / Polysaccharide
Benedicts
Color / Monosaccharide
Present? / Iodine Color / Polysaccharide
Present?
Peanut Butter / Slight green / A little
Apple / Red/orange / yes
Potato / Blue-1st
Green-2nd / A little, after cooked / black / yes
Marshmallow / Yellow/orange / yes / black / yes
Tortilla Chips / Slight green / A little / black / yes
Substance / Lipids / Protein
Sudan
Color / Lipids
Present? / Biuret
Color / Protein
Present?
Peanut Butter / Yellow,
bubbles / yes / Purple / yes
Apple
Potato
Marshmallow
Tortilla Chips / Yellow,
bubbles / yes

Questions

Why is a monosaccharide called a monomer?

A monosaccharide is called a monomer because monomers are the single parts, smaller parts that make up the macromolecules of life and monosaccharides, single sugar molecules, are the monomers that make up the macromolecule carbohydrates. Many monomers make up polymers, just like many monosaccharides make up the polymer, polysaccharide.

What is the test for a monosaccharide?

To notice if the Benedicts solution changed color. If it did, monosaccharides are present.

Why is a polysaccharide called a polymer?

Polymers are large macromolecules made up of smaller parts called monomers. A polysaccharide is a carbohydrate polymer made of smaller parts called monosaccharides. A polysaccharide is a specific example of a polymer.

What is the test for a polysaccharide?

To notice if the Lugols solution caused the food to change to black. If so, a polysaccharide like starch is present.

A lipid refers to three different types of substances, waxes, fats, and oils.

Why is distilled water a good substance for a control in this lab activity?

Distilled water is a good negative control because it tests negative in all the indicators because it does not contain lipids, carbohydrates, or proteins, the items we were testing for.

What conclusion could you make if a positive test for any of the organic compounds occurred in the distilled water?

I would conclude that water was contaminated in some way with one of the organic compounds we were testing for. For example, maybe someone was eating peanuts during the lab and they accidentally dropped some crumbs into the test tube. Another possibility is that perhaps the test tube used for a test was not properly cleaned and still had some residual food items from the group before.

Why can’t Biuret’s reagent be used to test for amino acids?

Biuret’s reagent is an indicator that detects peptide bonds which are the bonds between amino acids in a polypeptide or a protein. Therefore, Biuret’s detects if a protein is present. It cannot be used to test for amino acids because amino acids are not joined together by a peptide bond unless they are found in a protein.

The leaves of many plants are coated with a waxy substance that causes them to shed water. How would you expect this substance to react in the Sudan IV test?

Since waxes are made of lipids, I would expect the wax to form bubbles when it came in contact with the Sudan IV, like it did in the lab.

People with diabetes are instructed to avoid foods that are rich in carbohydrates. How could your observations in this investigation help you decide whether a food should be served to a person with diabetes?(explain the relationship between diabetes and monosaccharides and there connection to this lab activity... include citations to references)

People with diabetes do not produce enough insulin which is a protein in your body which delivers glucose from your blood into your cells. Glucose is the cells energy source. Diabetics should avoid food high in sugars because they need to watch their blood sugar levels. They are prone to high blood sugar levels because of insulin issues. High blood sugar can lead to sugars changing to fats and clogging the arteries in the body possibly leading to heart failure. We could use Benedicts solution to help us determine if a food has carbohydrates in it and if so advise the diabetic to limit their intake of that food.

In winter, plants exchange the saturated lipids in their cell membranes for unsaturated lipids. Unsaturated lipids are “bent” and keep the membranes more fluid, or pliable, because they cannot be stacked closely together. Of what advantage would this be for green stemmed (herbaceous) plants that live through the winter?

In winter the water inside plants’ cells may freeze in low temperatures. If their membranes were more flexible and pliable, then they would be able to withstand the pressure of the water expanded in their cells without rupturing a membrane. If membranes rupture, the cell dies. Also, if the plant were more flexible it could also bend more instead of break under the weight of snow and ice on its branches.

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