Scientific Method and Organic Molecules LAB
Name:
_________________
We’ve learned that there are 4 types of organic compounds: (1) carbohydrates, (2) lipids, (3)
proteins and (4) nucleic acids. All organic compounds are made from these 4 basic
macromolecules, including all the foods we humans eat… and we eat a great variety of foods.
In fact, we eat foods that come from plants, fungi, animals, protists, among others. That is why
humans are considered heterotrophic omnivores our foods are quite varied and they come
from both plants and animals.
Research
Plants produce starch to store energy, and sugars to provide energy and attract animals.
Animal tissues contain protein; and, may also contain lipids. Some plants produce lipids to
store energy in seeds. All cells contain nucleic acids, but we will not test for them today.
Organic Molecule Tests: Iodine turns from copper/amber to bluepurpleblack in the
presence of starch. Benedict’s Solution turns from aqua blue to yellow orangerustyorange when mixed with simple sugars (monosaccharide) and heated. Biuret’s Solution turns
from royal blue to violetdark purpleblack when reacting with proteins. When absorbed by
a brown paper bag, lipids will turn the paper shiny and translucent (light shines through).
Hypotheses
For each food sample state a hypothesis as to what will happen
Instant Potatoes will test positive for _____________________using ______________________
Peanut Butter will test positive for _______________________ using _____________________
Apples (or Any Juice) will test positive for _________________ using ______________________
Turkey or chicken meat will test positive for _______________ using _____________________
Table Sugar will test positive for _________________________ using _____________________
Gelatin or Whey Powder will test positive for ______________ using ______________________
Butter will test positive for _____________________________ using _____________________
Meat Broth will test positive for _________________________ using _____________________
Oil will test positive for ________________________________ using _____________________
Gatorade will test positive for __________________________ using ______________________
Splenda™ will test positive for __________________________ using ______________________
Powdered Corn (or Popcorn) will test positive for___________ using ______________________
Cheese will test positive for ____________________________ using ______________________
Mayonnaise will test positive for ________________________ using ______________________
Egg White will test positive for__________________________ using ______________________
Control(s)
Use water as a control (as in the videos)
Experiment
Test only 8 food samples; 2 from each group (Starch / Simple Sugars / Protein / Lipids). Follow
Dr. Snyder’s instructions.
Data
Enter your data in the chart on the reverse side of this sheet.
+ for Positive Test; the color changes should also be noted in the data chart.
- for Negative Test
© 2012 Dr. Snyder / LCHS
EXPERIMENT:
1. Each table group collects 8 Food Samples; 2 from each group that we are testing for.
2. Put ALL the foods on a brown paper towel and label them (you only need a small pinch
of each sample).
3. Test each food sample for the Organic Molecule you had predicted that it contained;
remember… you completed this on side 1 of this lab sheet.
4. Place a Positive Symbol (+) on the chart below, IF it tested positive (e.g., color change)
5. If it tested negative, then place a Negative Symbol (-) on the chart, and choose another
test for that sample.
6. Continue for each sample until you have a positive reaction for each.
7. Everyone needs to fill out this Lab/Activity Sheet and turn it in… even though you are
working in groups.
NOTES for SIMPLE SUGARS TEST with BENEDICTS SOLUTION
A. Put a pinch of your food sample in a test tube
B. Add ½ inch of water, put your thumb over the top of test tube and shake
C. Add 5-8 drops of Benedict’s Solution and shake again
D. Place it in the water bath for 5-10 minutes.
E. Record the color change
DATA TABLE
Food Item
Biuret’s
Solution
Iodine
Benedict’s
Solution
Brown
Paper Bag
1.
2.
3.
4.
5.
6.
7.
8.
ANALYSIS
Did your Hypotheses (predictions) you made on side 1 hold true? If NOT, then what new test
did you perform and why did you choose it?
What Chromatic Indicator changes did you spy during the 2 tests for simple sugars?
Why are there different Chromatic Indicators for these tests? What do they tell you about the
organic molecules in your food sample?
What errors might have occurred?
Would you do anything different if you reran the experiment?
© 2012 Dr. Snyder / LCHS