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Macromolecules: Identifying Carbohydrates and Proteins
Introduction and Background information:
Atoms are pure substances like Hydrogen, Oxygen, Carbon, Nitrogen, and Phosphorus. Scientists use the
Periodic Table of Elements to organize all pure substances on earth. Elements often join together (or bond)
through donating or sharing energy from electrons. When two or more elements join together we call this
a molecule. All living things are made a handful of the same molecules. The molecules essential for life to
function are called biomolecules and are considered “organic”. Carbon, Hydrogen, Oxygen, Nitrogen, and
Phosphorus are the five essential biomolecules. When big and bulky long chains of essential molecules bond
together they are called MACROMOLECULES. There are 4 categories of macromolecules that are found in
all living things: proteins, carbohydrate, lipids and nucleic acids.
Lab Objective:
To identify what kinds of food sources contain which category of macromolecule such as proteins and
carbohydrates (sugar and starches). Indicators are chemicals that will change color, form a precipitate
(residue) or bubble in the presence of specific molecules
Benedicts: Tests for Sugar carbohydrates. It will turn from blue to green-yellow or
orange the presence of sugars. The more yellow – the more sugar is present.
Lugols (Iodine): Tests for starch. It will turn from yellow-brown to purple-green
to indicate a starch is present.
Biurets: Tests for Proteins. It will turn from Blue –purple to a pink-orange
Background Information:
1. What are Proteins?
There is no life without protein. Next to water, protein is the most plentiful substance in your body.Proteins are
found in every part of your body, the skin, muscles, hair, blood, body organs, eyes, even saliva. Protein is
composed of smaller N-H groups known as amino acids. Food sources for protein include beef, poultry, fish,
and green vegetables. These amino acid chains inside a protein are called a peptide chain. Amino acids are like
the individual Lego bricks that fit together to build a bigger structure. Therefore, amino acids are often called
the “building blocks of protein.” There are more than 20 different amino acids. The suffixes -in, -ine
identify a protein, amino acid or nucleic acid. Examples: vitamin, pepsin, insulin, tyrosine, adenosine,
adenine, cytosine, guanine, thymine.
Proteins are macromolecules containing the element Nitrogen hooked to Carbon molecules. A protein is
composed of several amino acids (N-H) molecule groups that are linked together. Proteins have different
functions; they can provide structure (ligaments, fingernails, hair), help in digestion (stomach enzymes), aid
in movement (muscles), help us fight off infection and disease and play a part in our ability to see (the lens of
our eyes is pure crystalline protein). Protein forms the structural material of bodily tissues. Protein control
critical physiological function. Protein is used in the body to build, maintain, and repair body tissues. Protein
energy will be used only after other energy sources (carbohydrate and fat) are exhausted or unavailable.
2. The Structure of an amino acid building block.
***Look for the Nitrogen functional group attached to the Carbons to identify the
protein molecular structure. Proteins can have different special shapes. Nucleic acid
structures are smaller than the larger, sometimes floppy proteins. Often, proteins
can bend, stretch, fold, spiral or form branches. Think about how hair can be
straight, wavy, bouncy, curly, shiny and different colors. These characteristics are
from the proteins that found inside the hair!
3. ENZYMES- are special protein starters - (we will not be testing for these today)
Enzymes are special biological proteins (found in all living
things). Enzymes start, end and control all the body functions
like digestion, growth and development, and even dying.
Enzymes are known as “biological catalysts.” A catalyst
reduces the time in a chemical reaction in breaking apart or
changing the shape of molecules. Vitamins, like B6, are
catalysts in the body. Many vitamins like A,B,C,D,E, and K are
necessary for a healthy life. Therefore, using an enzyme will
lower the energy to start a reaction (called activation energy) and make the reaction move faster than if a
chemical reaction did not have an enzyme starter. Enzymes are usually identified by the suffix –ASE. For
Example: sucrase enzyme breaks apart sucrose sugar. Lactase enzyme breaks apart lactose sugar and Amylase
enzyme breaks apart amylose sugar.
II. What are Carbohydrate?
A carbohydrate is a compound called a saccharide and is made up of Carbon, Hydrogen, and
Oxygen. For animals, such as humans, carbohydrates are the fuel source to release an energy
molecule called ATP. Instead, carbohydrates are both a fuel and a support structures. Carbohydrates
can be categorized as simple sugars, starches and cellulose.

Simple Sugars are “monosaccharide” food sources that release energy and include honey, jams, jellies,
syrup, table sugar, candies soft drinks, fruits, and fruit juices. The body energy we get from sugar is a
molecule called glucose. Sugars like table sugar (sucrose), sugar in candy (dextrose) and sugar in fruit
(fructose) can readily be broken apart and converted into glucose by enzymes in different parts of the
body.

Starch is the building material for plants and is used for support and structure. Some examples of
starches are wood, potato, potato chips, French fries, flour, grains, rice and bread. Starches are often
sticky like glue, hold things in place, and are edible. It takes a little longer for the body to digest starches
but they can be reduced into glucose.

Cellulose is unique. Cellulose is a sugar but acts like a starch. In other words, cellulose is a sugary
energy source and a building material for plants…it is the chief component in stems, tree trunks, leaves
and plant cell walls. Cotton is a pure form of cellulose and it can be woven into fibers. We eat corn, but
we wear cotton. Unfortunately, human do not have the correct enzymes to break apart cellulose in our
stomachs. Cows and organisms inside a termite stomach can digest cellulose. In our stomachs,
undigested plant materials such as, corn, passes through our stomach and intestines almost untouched.

Monosaccharide =1 sugar ring, disaccharide =2 sugar rings polysaccharide =several sugar rings
1. Structure of Carbohydrates

Notice the CHO…straight chains or branches are starches.

Sugars have a rings forming 5 or 6 carbons
- The suffix -OSE means sugar
Method:
1) Label all your test tubes. Write the food on each test tube in your experimental group. Label one test tube as
water. This is your control group.
2) Add 10 ml of water to every test tube. The water level is a constant variable
3) Place a small quantity of a food item in each of the different experimental test-tube (the amount is about the size
of a pencil eraser.)
4) Add 2 pipettes of the indicator you were assigned into each test tube. Draw your “before heat” test tube
observations. Use color pencils.
5) Place all tubes in a beaker with water and heat for 3 minutes. Draw your “after heat ” test tube observations.
6) Clean your test tubes and rinse out your test tubes.
7) Repeat steps 1-6 with each of the other indicator
Post Macromolecules Lab Questions for your Lab Report
1) What is the objective of this lab? (Topic Sentence)
2) Identify the two macromolecules we tested for in this lab (Introduction Paragraph)
3) Identify the Experimental Group: _______________________________
4) Identify the Independent Variable: ______________________________
5) Identify the Dependent Variable: _______________________________(measured and
responds)
6) Identify the Control Group:
________________________________
7) What is the function of the control group? ______________________________
8) Describe control factors that we kept constant (the same or equal)
9) Complete the background knowledge chart for each of these macromolecules.
(Supporting paragraph in the Introduction with facts)
Macromolecule
List 2
Describe the
2 source where
What
Describe the
examples of
function(s) of
you can find in
essential
indicator and the
this
this
foods this
elements
color change that
macromolecule
macromolecule.
macromolecule
make up the
will occur if this
molecular
molecule is present
structure?
in a food source
Ending with –
ine, in, or ase
Protein
Carbohydrate
Ending with
Sugar
-ose
Carbohydrate
-ide
Starch
10) Your Reflection on this lab: (This will be part of your Conclusion) Yes, you may write
sideways for more room.
Did you like
Describe two
How do you
How were your
How has this lab
this lab? Why
things you
think repeating
results the same
changed your
or why not?
learned from
this experiment
or different
knowledge
observing your
might provide
when you
about
test tubes.
different
compared your
macromolecules
Identify which
results?
results to
test please.
another team?