Download Name Date Period Identifying Organic Molecules

Name ____________________________ Date _______________ Period _____________________
Identifying Organic Molecules- Makeup
Instructions: Please write on your own notebook paper. First copy the introduction and problem sections
with the headings. Then, read all the scenarios under the lipid, carbohydrate, and protein for each section then
answer all the questions for each. You do not have to write the questions just your answers.
Introduction
The most common organic compounds found in living organisms are lipids, carbohydrates, and proteins.
Substances called indicators can be used to test for the presence of organic compounds. An indicator is a
substance that changes color in the presence of a particular compound. In this investigation, you will study
several indicators to test for the presence of lipids, carbohydrates, and proteins.
Problem
What are the major types of organic compounds in some common foods?
Lipid
A scientist is testing different substances to see if lipids are present. The best way to complete this test is to
touch each of the compounds to see if any are greasy. He touches several substances and notices many are
greasy to the touch, such as ground up lettuce with water, corn oil, peanut butter, and ground up potato with
water. Some of the substances he touches are not lipids but feel greasy anyway.
1) Based on your knowledge of lipids, which of the following compounds, lettuce, potato, corn oil, and butter,
is a lipid. Please explain why you chose this specific compound?
Carbohydrates
Part A
Scientists are able to identify glucose in a carbohydrate by conducting a test using benedict’s solution. The
scientist added benedict’s solution to the each of the solutions below and heated the substances up to cause
the reaction to occur. Benedict’s solution will change to a brown, yellow, orange color when sugar is
present in a compound and remain blue if no change occurs.
Substance
Color Change
Lettuce mixed with water
Egg White
Corn Oil
Apple Juice
Honey
Vegetable Oil
Orange
Yellow
Blue
Yellow-Orange
Orange
Blue
Name ____________________________ Date _______________ Period _____________________
1) What is the indicator used in this experiment? How will you know if a sugar is present?
2) Name which substances indicate they have sugar.
3) Name which substances did not show any reaction. What type of macromolecule are these solutions?
Part B
A class is determining which substances contain starches. The students conduct a test using a reagent called
iodine. The teacher tells the students that if a substance tests a positive for starch it will turn from yellow
brown to a dark bluish black color. The students are working with several substances and receive the
following results:
Substances
Chemical Change
Distilled water
Potatoes with water
Corn oil
Apple Juice
Yellow-orange
Bluish Black
Yellow Orange
Yellowish
1) Explain the purpose of distilled water in this experiment
2) What substance tested contains starch? Explain why you are stating this as your answer?
3) Why would a substance that is carbohydrate not change in the presence of benedict’s solution and change in
the presence of iodine?
4) What is the indicator in this experiment
Proteins
A class is testing substances to see which ones contain proteins. Each member of the class is given egg whites,
gelatin, distilled water, and an unknown. The students add each solution to the test tube and add the reagent,
biuret reagent, to find out which substances are proteins. If a substance is protein, the biuret will turn the
substances to pink or purple color.
The students tested distilled water, corn oil, egg white, and gelatin. The gelatin and egg white turned to a
purple/pink color. Though, the distilled water and corn oil remained blue.
1) What is the indicator in this reaction?
2) Which substances tested contain protiens?
3) State which substances did not react and why?