Organic Molecule Identification Lab
Please do not write on this sheet of paper - To Be Retuned at the End of the Lab
Please read the entire lab and then answer the following questions IN YOUR LAB NOTEBOOK before you begin:
Pre-LAB Questions
1. Read through this entire lab and then describe the purpose of this lab.
2. What are your two unknown samples (that you will be bringing from home)?
3. What is your hypothesis about the composition of these items?
.
Part A: Protein Identification (Add these procedures in your lab notebook)
Background: The test used to identify protein is technically called the xanthoproteic test. A substance containing protein will turn
yellow when nitric acid is added to it. No color change to yellow indicates that the substance being tested has no protein.
1.
2.
Put on goggles, tie your hair back if needed and put on your lab apron BEFORE you begin!
Using a spot plate, add each of the following substances to one of the depressions:
fingernail clipping
egg white, hard boiled
absorbent cotton
cheese
cream cheese
dog hair (white/cream colored only)
your sample #1
your sample #2
Take your spot plate to the fume hood on the LEFT side of the room.
Add 3-5 drops of concentrated nitric acid to each depression (YOUR TEACHER WILL DO THIS!)
CAUTION: Nitric Acid is harmful to skin and clothing
Wait two minutes, then record the color of each of the items on the Data Table You have created in your Lab Notebook
(See Sample Below). On the basis of the xanthoproteic test, indicate in the last column of the table if the substances
tested do or do not contain protein.
After you record your data, sprinkle baking soda over the spot plate under the fume hood and empty the contents into the
garbage and then rise with water. Clean and dry the spot plates thoroughly within the classroom and return them to the
place you got them.
3.
4.
5.
6.
Data Table 1: Protein Identification (draw this data table in your lab notebook)
SUBSTANCE
COLOR CHANGE (describe all
qualitative data here)
PROTEINS (Yes or No)
Finger Nail
Egg White
Cotton
Dog Hair
Cream Cheese
Your Sample #1:
Your Sample #2:
Part B:
1.
2.
3.
Lipid Identification (add these procedures in your lab notebook)
On separate pieces of brown paper bags, dampen and rub some of your sample #1, sample #2.
Allow the paper bags to dry for a few minutes.
Place the paper bags on the light table. If light passes through, a translucent (semitransparent) spot will form. If
translucent areas appear than lipids are present. Record if lipids (fats) are present in Table 1.2.
Data Table 2: Lipid Identification
SAMPLE
Cheese
Potato Chip
Your Sample #1
Your Sample #2
TRANSLUCENT (yes/no)
LIPID PRESENT (yes/no)
Part C: Carbohydrates Identification
Benedict's Test
•
Number six clean test tubes 1-6. Fill each test tube about a little finger's with full by adding the following:
Test tube 1 - honey Test tube 2 - table sugar solution Test tube 3 - apple juice
Test tube 4 - powdered sugar solution Test tube 5 - your sample #1 (add water) T est tube 6 - your sample #2 (add water)
•
Add 30 drops of Benedict's solution to each test tube (figure 8).
•
Place all 6 test tubes into a hot water bath for 5 minutes.
•
Remove the test tubes from the bath with a test tube clamp and note any color changes. Record the color of the solutions in
Table 3 (at the bottom of the page) in your Data Sheet.
NOTE:
A color change may or may not occur when Benedict's solution is added to a carbohydrate and then heated. A
change from blue to green, yellow, orange or red occurs is monosaccharide is present. If this test shows
monosaccharides present, place a "M" in the "Type" column of the Data Sheet Table 1.3. The original blue color will
remain after heating if monosaccharide are not present.
Iodine Test
•
Prepare 6 more test tubes containing the same substances just used (honey, table sugar solution, and so on). Do not add
Benedict's solution.
•
Add 4 drops of iodine solution to each tube (see figure 6 above).
NOTE:
A color change may or may not occur when iodine solution is added to a carbohydrate. A change
from its original
rust color to deep blue-black occurs if a polysaccharide is present. If this test shows polysaccharides present, place a
"P" in the "Type" column of the Data Sheet Table 1.3. If no color change occurs, polysaccharides are not present.
Data Table 3: Carbohydrate Identification
SUBSTANCE
Honey
Table Sugar Solution
Apple Juice
Powdered Sugar Solution
Sample #1:
Sample #2:
BENEDICT'S
COLOR CHANGE
IODINE
COLOR CHANGE
TYPE
In your lab notebook after your data tables please include the following:
Analysis Questions
Use your results from the previous lab to answer the following questions.
Part A
1. Name four amino acids.
2.
a) How many amino acids are there?
b) How are amino acids used by living things?
3.
List several body parts made of proteins.
4.
Name the four chemical elements that are present in all amino acids (consider the ones we have studied).
5.
Name the two special end groups present in amino acids.
6.
What element is present in proteins (amino acids) that was not present in carbohydrates (think back to the macromolecule lab)
7.
Explain how a protein molecule is formed by living things.
8.
Explain how one protein differs from another protein.
9.
Describe how to tell if a substance is a protein by using the xanthoproteic test.
10. List those substances tested that contain protein.
11. List those substances tested that were not protein.
12. Using what you have learned about proteins, decide which of the following substances contain protein.
a) hamburger b) chicken c) peanut oil d) maple syrup e) liver f) human hair
g) a stomach
h) 207 joined amino acids
13. In Latin, the word "xantho" means yellow, and "proteic" means protein. Why is " xanthoproteic" a meaningful word to use
when describing a chemical test used for identifying a protein?
Part B
1. What is a lipid and what are examples of different types of lipids.
2.
Why are lipids important in the human body?
3.
What chemical elements are present in lipids.
4.
What are the main monomers that make up lipids?
5.
What substances did you test that had lipids in them?
6.
What are the molecular differences between saturated and unsaturated fats? In what types of food would you expect to find
them?
Part C
1. Name the three types of carbohydrates.
2.
What three elements are present in all carbohydrates?
3.
Give to examples of sugars that are:
a) monosaccharides
b) disaccharides c)polysaccharides
4.
How can you tell by using Benedict’s and iodine solutions if a sugar is a disaccharide?
5.
A certain sugar has no change in color when tested with Benedict’s solution. Can you tell what type of saccharide it is?
Explain your answer.
6.
A certain sugar has a color change in Benedict’s solution. Can you tell what type of saccharide it is? Explain your answer.
Give an example of a food that is a a) monosaccharide
b) disaccharide c)polysaccharide