Name(s)____________________________________
Date_____________________
MOD____________
Writing a Lab Report (you can use this paper for a rough draft) Turn in with
your final report
Must be typed in YOUR words
(2pts) TITLE: The title should clearly describe the topic of the report. Place your full name and MOD below the title.
(4pts) Background: Research about the topic(s). This should be at least 4 sentences for each topic. Include your source.
(6pts) Question/ Purpose/ Objectives: what problems are you trying to solve and why?
(4pts) HYPOTHESIS: Write a statements (if-then)to express your expectations of the results and as an answer to the problem
statement.
(3 pts) MATERIALS: List all laboratory equipment and other materials needed to perform the experiment.
(8pts) PROCEDURE: Describe each step of the procedure (in your own words) so that someone else could perform the experiment following your directions.
1
(12 pts)RESULTS/ conclusions: Any Data?
Record your conclusions in a paragraph at the end of your report. Your conclusions should be an analysis of your collected data. Did
you answer your questions?
Can you accept or reject your hypothesis?
LAB: Tests for Organic Compounds (pick one experiment only to do your lab
report on)
READ: Understanding the chemistry of living organisms is an important part of biology. The structures of cells
are made up of many different chemical molecules. Cell metabolism involves the production and destruction of
many types of molecules. Most of the common molecules found in living things belong to four classes of
carbon-containing molecules: carbohydrates, lipids (demo only in class), proteins, and nucleic acids. You
must type a formal lab report and submit it with all your results. This paper is a guide to help you complete
your lab report.
Objectives
 Determine the presence of starch by a chemical test.
 Analyze a glucose solution for the presence of simple reducing sugars.
 Analyze a sample of gelatin for the presence of protein.
Materials:
(may
not
use
laboratory apron
safety goggles
gloves
hot plate
water bath
test tubes (3)
test-tube rack
test-tube holder
test-tube brush
all
depending
on
which
lab
you
choose)
wax marking pencil (or masking tape and
marker)
soluble starch solution
95% ethanol
biuret reagent
benedicts solution
2% gelatin (or egg whites mix 1 egg with 20 mL
water) solution
glucose solution
2
Procedure:
Tests for Carbohydrates
Test for Starch Day 1
1.
Put on goggles and an apron. Label three test tubes 1, 2, and 3. Place them in a test-tube rack.
2. Using a separate dropper for each solution (DO NOT cross contaminate), add 20 drops of soluble
starch solution to test tube 1, 20 drops of glucose solution to test tube 2, and 20 drops of water to test
tube 3. Record the color of each tube’s contents in Table 1.
3. Add 1 drop of iodine solution to each test tube. CAUTION: If iodine is spilled, rinse with water and call
your teacher immediately. (Gloves)
4. Record in Table 1 the color of each tube’s contents after addition of the iodine. A blue-black color
indicates the presence of starch.
5. Discard the contents of the test tubes according to your teacher’s directions. Gently use a test-tube
brush and soapy water to clean the three test tubes and rinse with clean water.
Test for Simple Reducing Sugars Day 2
1. Heat the water bath to boiling on the hot plate.
2. Label three test tubes 1, 2, and 3.
3. Using separate droppers for each solution, add 10 drops of soluble starch solution to test tube 1, 10
drops of glucose solution to test tube 2, and 10 drops of water to test tube 3. Record the color of each
tube’s contents in Table 2.
4. Add 10 drops of Benedict’s solution to each of these three test tubes and place in a boiling water bath
for 3 minutes.
Benedict’s solution tests for the presence of simple reducing sugars (monosaccharides and some
disaccharides, but not polysaccharides). Thus, a color change might or might not occur when
Benedict’s solution is added to a carbohydrate and heated. A change from blue to green, yellow,
orange, or red occurs if a monosaccharide or some disaccharides are present. The original blue
color will remain after heating if a polysaccharide or some disaccharides are present.
5. Remove the three test tubes from the water bath using a test-tube holder and place them in a test-tube
rack to cool. CAUTION: Be careful not to burn yourself. If Benedict’s solution is spilled, rinse with
water and call your teacher immediately.
6. Record the color of each tube’s contents in Table 2.
7. Discard the contents of the test tubes according to your teacher’s directions. Gently use a test-tube
brush and soapy water to clean the three test tubes and rinse with clean water.
3
Part C: Tests for Proteins Day 2
1. Label three test tubes 1, 2, and 3.
2. Using separate droppers, add 30 drops of egg whites to test tube 1, 30 drops of glucose solution to test
tube 2, and 30 drops of water to test tube 3. Record the color of each tube’s contents in Table 5.
3. Add 10 drops of biuret regent to each test tube. CAUTION: Biuret reagent is extremely caustic to the
skin and clothing. If biuret reagent is spilled, rinse with water and call your teacher immediately.
When biuret reagent is mixed with a protein, it will produce a lavender to violet color.
4. Record in Table 5 the color of each tube’s contents after adding biuret regent.
5. Discard the contents of the test tubes according to your teacher’s directions. Gently use a test-tube
brush and soapy water to clean the test tubes and rinse with clean water.
6. Fill in the column of all five tables with the correct interpretation of the test results.
DATA and OBSERVATIONS (these are sample charts and suggested questions to help you organize
your thoughts. MAKE YOUR OWN tables/charts and YOUR OWN conclusions.
Table 1:
Corn starch
Test for Starch Day 1
Test tube
Substance
1
Starch
2
Glucose
3
Water
Color at start
Color after
adding iodine
Starch present
(+/-)
Table 2:
Test tube
Substance
1
*Starch
2
Glucose
3
Water
Test for Simple Reducing Sugars Day 2
*Benedicts won’t change for a polysaccharide (starch)
Color after
Color after
adding
heating
Color at start
Benedict’s
solution
Reducing
sugars present
(+/-)
4
Table 3:
Test for Proteins
Test tube
Substance
1
Egg Whites
2
Glucose
3
Water
Color at start
Day 2
Color after adding
biuret regent
Protein present
(+/-)
ANALYSIS (use this and the data for your conclusions)
1.
What is used to test for the presence of starch? ___________________________________________
__________________________________________________________________________________
2. How can you tell by using this test that a substance contains starch? ___________________________
__________________________________________________________________________________
3. What is used to test for the presence of simple reducing sugars such as monosaccharides? ________
__________________________________________________________________________________
4. How can you tell by using this test that a substance contains a simple reducing sugar? ____________
_________________________________________________________________________________
5. Why was water tested for each chemical? ________________________________________________
__________________________________________________________________________________
6. What is used to test for the presence of protein? ___________________________________________
7. How can you tell by using this test that a substance contains protein? __________________________
__________________________________________________________________________________
8. Biuret regent will turn the skin brownish-purple. Explain why this occurs. ________________________
__________________________________________________________________________________
5