Data Table:
Substance
Monosaccharide
Polysaccharide
Peanut Butter
Benedicts
Color
Slight green
Monosaccharide
Present?
A little
Apple
Red/orange
yes
Potato
Marshmallow
Blue-1st
Green-2nd
Yellow/orange
Tortilla Chips
Slight green
Substance
Peanut Butter
Iodine Color
Polysaccharide
Present?
A little, after
cooked
yes
black
yes
black
yes
A little
black
yes
Lipids
Protein
Sudan
Color
Yellow,
bubbles
Lipids
Present?
yes
Yellow,
bubbles
yes
Biuret
Color
Purple
Protein
Present?
yes
Apple
Potato
Marshmallow
Tortilla Chips
PB—left grease spot, translucent
Apple
Marshmallow
Tortilla Chip-- left grease spot, translucent
Potato
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.
www.diabetes.org
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.
.
http://www.occc.edu/biologylabs/index.htm Go to this website for the Virtual Lab.