Macromolecules – The Building Blocks of Cells
We can begin to understand what we are made of by thinking about what we eat. The food we eat is
directly linked to the requirements of cells for one of three main purposes:
1. As a physical building material for cell parts
2. As a source of cellular energy
3. To maintain homeostasis (a constant internal environment)
The total amount of available
energy stored in this food
Used to make membranes. This
is the main structural
component of cells.
Membraned structures include the cell
membrane, nucleus, mitochondria, ER,
vacuoles and Golgi
All values presented are in reference
to a single serving size. If you eat
more than one serving, the DV
values will increase.
example of a Canadian food label
Fats are also stored in
specialized cells for long-term
energy storage.
A component of the cell
membrane
This tells you if there is a little or a
lot of a nutrient in one serving.
When choosing foods to eat, we
often look for foods with a lower
percent DV of fat, cholesterol,
sodium and carbohydrates and a
higher percent DV of fibre, protein
and essential vitamins / minerals.
Tips for reading food labels:
 Calories are less important than
ingredients.
 Always compare your portion to
the serving size.
 Fibre does not raise blood sugar
and should be subtracted from
the total carbohydrate
(ie. 36 g carbohydrate – 6 g fibre
= 30 g available carbohydrate).
 Choose foods high in fibre. Aim
for 25 g or more of fibre per day.
 Try to avoid foods with 400 mg
of sodium or more per serving.
Involved in some cell functions
and important for your body`s
water balance.
Sugars are used to generate
cellular energy.
Fibre is important for proper
digestion and a healthy gut.
The material used to make
enzymes and the molecular
machines that makes cells
perform specific functions.
Essentially, your cells are made from just 4 main types of molecules:
Main
function(s)
Carbohydrates
(Sugars)
Lipids
(Fats)
Energy
Membranes
Glucose
Examples
Starch
Cellulose (fibre)
Subunits
monosaccharides
Phospholipids (membranes)
Proteins
Enzymes +
Molecular machines
Nucleic Acids
Genetic Code
Limitless variety:
Triglycerides (fat / oil)
Muscle fibres, hair, mucus,
amylase, ion channels
DNA + RNA
glycerol + fatty acids
amino acids
nucleotides
Life is COMPLEX!
How can all living cells be made from just 4 types of molecules?
ANALOGY:
Think about LEGO. From only a few different kinds of pieces, you can assemble them into
almost anything. Polymers can be thought of as the chemical equivalent of LEGO. Three of
the four macromolecules of life are polymers and can therefore be used to construct highly
complex and varied chemical structures. The most varied and complex structures can be
made from proteins.
Polymers:
Polymers are large molecules made from linking subunits called monomers.
Man-made polymers like plastics, nylon, and Kevlar use only one or two simple monomers that are
linked together into massive polymer chains.
Polyethylene (a typical plastic)
Kevlar (monomer in bold)
Living cells make polymers from a wider variety of monomers and can assemble them with more percision at the
molecular level. Proteins are the most complex polymers used by living things. They can arrange their 20
different monomers in any order and in any length. This allows cells to assemble proteins to do just about
anything a cell needs.
The 4 Macromolecules of Life
Carbohydrates
Proteins
Nucleic Acids
Carbohydrates like starch, glycogen,
and cellulose are long polymerized
chains of glucose in different
arrangements. “Simple sugars” like
glucose and fructose are carbohydrate
monomers, while “complex sugars”
are their polymers.
Proteins make a much greater
variety of complex structures
than any other biological
macromolecule. They do this
by linking 20 different types of
amino acids in endless
different combinations.
These long chains of
thousands of amino acids
then fold into complex 3D
shapes. The folding of these
molecules turns them into
microscopic tools and
machines.
Nucleic acids like DNA use 4
different monomers (called
nucleotides) in the same way we
use letters to make words. The 4
nucleotide letters are linked into
long strings of written code.
Each three letter word codes for
one of the 20 amino acids. This
makes DNA like a recipe book for
how to build specific proteins.
Note: They are not on dietary labels
because you can make nucleotides from
available nutrients
Lipids
The fourth macromolecule of life is not a polymer, but it is made of Lego-like subunits that can be
arranged in different ways to change their properties.
Triglycerides
Phospholipids
Triglycerides are fats and oils.
Some cells store these molecules
as backup energy. Since they are
nonpolar, they are stored
without water to remain
lightweight
Phospholipids are the most
important lipids because they
form membranes. This is the
main structural component of all
cells.
Steroids
Steroids are derived from fatty
acids and serve as a membrane
component (cholesterol) and as
chemical signals (hormones).
PRACTICE!
Answer each of the following questions on a separate piece of paper.
1. a) What is a polymer?
b) What is a monomer?
c) Draw a simplified diagram of a polymer that labels both the monomer and polymer.
2. What are the monomers of each of the following?
a) proteins
b) carbohydrates (specifically starch, cellulose and glycogen)
c) DNA
3. What is the main function of phospholipids?
4. a) Compare the following food labels for canned soup. If canned soup was part of your regular diet,
based on the nutritional information, which would you choose more often and why?
Canned Vegetable Soup
Canned Cream of Mushroom Soup.
b) If a can of concentrated mushroom soup makes about 2 cups of soup and you ate it all yourself,
how much of your daily value of sodium would you get?
c) Using the nutrition facts for vegetable soup, state at least one important thing that your cells do
with each item present (more than 0 g) from fat to protein excluding sodium.
5. a) How does DNA code for proteins
b) Why does DNA only code for proteins?
(in other words, why are cells able to do whatever they need just by making the right protein, at
the right place, at the right time?)
6. Write a paragraph explaining why the chemistry of cells can be compared with using Lego.