SBI4U1/3/6
Biochemistry
Identifying Macromolecules in Food Substances
Introduction
All living organisms are composed of various types of organic molecules such as carbohydrates, proteins,
lipid and nucleic acids. These substances can be detected by simple chemical indicator tests that show a
colour change in the presence of the macromolecule.
Part A: Using various food substances, identify the macromolecule
that is detected by each of the 3 chemical indicators.
The infamous Claw has struck! It has broken
into the biology lab and mixed up the chemical
indicators. It is your job to sort out this mess
and identify what each indicator tests for.
The 3 chemical indicators have now been
labelled reagent 1, 2 and 3. Each indicator
detects only one of the following classes of
macromolecules:
 Monosaccharides
 Reducing disaccharides
 Non-reducing disaccharides
 Polysaccharides
 Amino acids
 Proteins
You will use the food substances listed below
to determine what each reagent tests for.
 Arginine
 Dextrose
 Gelatin powder
 Saltine crackers
 Table sugar
 Malted sugar
Instructions (work in groups of 2-3)
1.
2.
3.
4.
5.
6.
7.
8.
Discuss in your group which of the food substances listed
can be used to identify each class of macromolecule.
In the space on the next page create an observation table
to record the results.
Show your chart to your instructor for approval. Make
changes as needed.
Perform the chemical indicator tests by following the
procedures provided at each station recording your
observations on the chart you created.
Form conclusions based on the results. Record your
conclusions in the chart below.
Bring your observations and conclusions to your
instructor. Your instructor will confirm your conclusions
when he/she decides that you have thoroughly
investigated the problem.
Perform any additional tests as needed as suggested by
your instructor. Once you have the correct findings and
instructor approval then proceed to part B.
Complete the post-lab reflection as homework. It is due
with the lab write-up.
Part B: Using chemical indicators to test for the presence of
carbohydrates and proteins in unknown white powders.
The Claw has struck yet again! This time it ransacked Bulk Barn and mixed up the labels to all the white powdered
products. Your job is to determine what the unknown substance is by using the chemical indicators from the lab.
Instructions
9. Obtain an unknown powder from your instructor. Record label on the container here:
10. Perform the 3 reagent tests on the powder to determine the macromolecule(s) present in the powder. Record
your findings. If you are unsure about your results and there is time, you may repeat any of the tests.
11. Make conclusions about the macromolecules present in your unknown.
Part C: Two-Page Lab Report


Individually hand in the lab write-up following the outline below.
As a group hand in a completed lab sheet. Do NOT retype it.
Lab
[A:10]
Language &
layout [C:5]
Observation
Table [C:5]
Report (Body) [A:20]
Description
 Suggest the macromolecules identified by each reagent. Explain how you came to these conclusions supporting your
answer with appropriate observations from the table of observations. Your explanation should NOT restate everything
on the observation table.
 Justify the type of macromolecule tested by each reagent by identifying all the food substance that is of the same class
(family) of macromolecule (e.g. fatty acids and triglycerides are from the same class). Discuss why certain members of
the class tested negative and how that impacts your conclusion. (e.g. it triglycerides test positive but fatty acids test
negative, what would that imply?)
 Do NOT attempt to identify the reagents. That is NOT the purpose of the lab.
 When referring to the observation table, you need to refer to the table numerically text (i.e. Refer to figure 1). The table
should follow after the text that refers to it. It should NOT precede the text. See textbook for examples of how figures
are incorporated into text.
 If there are results that fall outside the pattern (anomalies) for each reagent’s identification, they should be identified
and explained (i.e. why was a there a colour in reagent X with food substance Y but it wasn’t considered a positive
reaction?).
o Sample paragraph: Reagent 5 tests for oxygen because both water and carbon dioxide changed to a
yellow colour whereas methane stayed the original blue colour. However, ethanol, which also contains
oxygen, didn’t turn yellow, but rather turned orange. One reason could be that the original ethanol
colour was red, which when mixed with yellow, would result in an orange colour.
 Suggest what macromolecule(s) is/are present in the unknown powder and which macromolecule it can’t be.
Support your answers with your observations but without rewriting the observation section.
 Suggest which substance your unknown could be. The list of possibilities is limited to: infant formula, protein powder,
tapioca powder, whole milk powder.
o Provide reasons for your choice.
o Explain why the other possibilities were eliminated.
 Embedded citations are needed if you are quoting data from a particular source.
 Appropriate choice of references (APA format) should also be appended to the end of the report. The references do not
count in your 2 page limit.
 Your observation table should incorporate data from both part A and B. Merge the observations from part A and B
onto ONE table.
 Table must be accurately and thoroughly completed.
 Tables must be properly titled with a figure number.
 Table must have an appropriate title. “Observation Chart” is NOT an appropriate title. Your title should be a sentence
rather than a headline. See any figure in your textbook for an example of what proper titling is like.
 Table should not break across two pages.
Even though this is not a complete lab report, all aspects should be treated as a formal report.
 Proper sentence and paragraph structure.
 No irrelevant or redundant information.
 No grammar or spelling errors. Proper capitalization and punctuation.
 Written in a past, passive voice; therefore no personal pronouns.
 Ideas should flow logically. Content is organized. Writing should be clear and concise.
 Font size minimum 11 point. Margin minimum 0.5”.
 Completion of all the tables in this lab sheet (One per group)
 Included notes of teacher comments / suggestions (One per group)
 Accurate answer of post-lab questions (One per group)
 Punctual. Prepared. Proper lab attire & behaviour. Thorough cleanup. Safe environment.
Limits
Three
paragraphs.
One
paragraph
about each
reagent.
No more
than 500
words.
Should take
up no more
than 1 page
Total of 2
pages.
Whole write
up should
not exceed
1000 words.
Sample Report Layout
Lab Title, Your Name, Date, Class code
Text suggesting the macromolecules identified by reagent 1 supporting
answer with data. Identify and explain any anomalies with reagent 1.
Text suggesting the macromolecules identified by reagent 2 supporting
answer with data. Identify and explain any anomalies with reagent 2.
Text suggesting the macromolecules identified by reagent 3 supporting
answer with data. Identify and explain any anomalies with reagent 3.
The figure. In this case is an observation table containing all the
data collected in both part A and B with an appropriate title and
figure number.
Text suggesting the macromolecules present in the unknown with
reasons.
Text suggesting which substance the unknown could be within the
given list of choices (see lab) with reasons and why not the other
choices.
APA References
SBI4U1/3/6
Biochemistry
Identifying Macromolecules in Food Substances
Group:
Create an observation table in the space below.



The chart should list each of food substances and the class of macromolecule it would help to identify along with the results
from each of the indicator tests.
Make sure that your chart has a place to record the original colour of the indicator.
Approval:
Provide an appropriate title for your chart. The title should be descriptive (a sentence fragment rather than
a headline) that provides details needed to understand the chart without having read the experiment.
Approval:
Conclusions formed from Observations in Part A
Reagent
Which
macromolecule
is detected?
How do you
know?
1
2
3
Post-lab reflection
a.
Define negative control.
b.
What did you use as the negative control in this experiment?
c.
If a negative control has a positive result, what could be the cause (i.e. what problem does this indicate)?
d.
Define positive control.
e.
If a positive control shows a negative result, what problem does this suggest?
f.
This experiment did not have any positive controls. What implications could this have?