Name: ______Date: ______
Organic Molecules Virtual Lab
http://www.okc.cc.ok.us/biologylabs/Documents/Organic%20Compounds/Organic%20Compounds.htm
In this lab you will study carbohydrates, proteins and fats. You will learn how to test for each of these organic molecules by performing these experiments. Complete each of the tests for carbohydrates, proteins and fats. When you have finished, continue to the ‘foods’ section to test for the presence of organic compounds in various common foods.
Carbohydrates-Monosaccharides are single sugars that react with a mixture called Benedict’s reagent or Benedict’s solution. The reaction changes the color of the reagent to green, red, or orange depending on how much sugar is present. Benedict’s reagent can be used to test for the presence of many of the simple sugars.
Pre-lab:
What is a reagent?
What simple sugars does Benedict’s reagent test for?
How can Benedict’s reagent be used to determine if a person potentially has diabetes?
Lab:
1. Draw the monosaccharide molecules shown on the carbohydrates page.
2. Complete the experiment that follows with Benedict’s reagent.
a. What reacts with simple sugars?
b. What happens to the reagent when it is heated and sugars are present?
c. Record the color of the liquid in the tube with Benedict’s after it has been heated.
d. Record the results after glucose has been added.
e. Which test tube is positive for simple sugars and which is negative?
f. What are the main elements in a carbohydrate and what is the general formula for them?
Pre-lab:
1. What is starch?
2. Where is starch found?
3. What happens to starch in our bodies after we eat it?
4. What in the starch is responsible for the coloring when it comes into contact with Iodine – KI reagent?
Lab:
1. Complete the experiment that follows with Iodine-KI reagent.
a. What is the color of the test tube with 2mL of Iodine-KI reagent?
b. What color is it after corn starch is added to it?
c. Which test tube is a positive test for starch and which is a negative?
Proteins-Proteins react with Biuret reagent. The reaction turns the color of Biuret from a light blue to violet.
Pre-Lab:
1. What Biuret’s reagent made from?
2. What is the principle of the Biuret Test?
3. What is it used to test for in the medical field?
Lab:
1. Draw the protein molecules shown on the proteins page.
2. Complete the experiment that follows with Biuret reagent.
a. What happens to the Biuret reagent when in the presence of protein?
b. Record the color of the liquid in the tube with the biuret reagent.
c. What color is it after 2 mL of protein solution has been added?
d. Which tube is positive for protein and which is negative?
e. What are the main elements of a protein?
Lipids- Sudan IV is a dye that will dissolve in fats. It will not dissolve in carbohydrates or proteins. Sudan IV will change the color of a fat.
Pre-Lab:
1. What color will Sudan IV change in the presence of fat?
2. Predict what will happen if Sudan IV is dropped into a test tube of water mixed with whole peanuts? Explain.
Lab:
1. Draw the fat shown on the fats page.
2. Complete the experiment that follows with Sudan IV.
a. What will happen to the Sudan IV when there are fats present?
b. Record the color of the liquid in the tube with the Sudan IV.
c. What color is it after 2 mL of oil has been added?
d. Which tube is positive for fat and which is negative?
e. What are the mail elements in fats?
Foods: Investigate each of the following food items to test for simple sugars, starch, protein and fat. Mark + for a positive test and a – for a negative test.
Food / Simple Sugar / Starch / Protein / FatPotatoes
Orange Juice
Nuts
Eggs
Salmon
Milk