What are macromolecules?
Cells are built primarily from the largest organic molecules-- the organic macromolecules.
Most of these organic macromolecules are themselves built by assembling smaller organic
molecules (like sugars for example) into long chains. There are four types of organic
macromolecules:
Carbohydrates
Lipids
Proteins
Nucleic Acids
You should learn this list so well that you don't even hesitate to say what the four types of
organic macromolecules are. This list is really important to understanding cells, so really
memorize it well. It will pop up again and again throughout the semester.
Carbohydrates are the "sugars." Both the simple sugars (like glucose and table sugar) and
complex sugars (like starch). The complex sugars are the macromolecules.
Lipids include the fats and oils. This is the only group that contains molecules that cannot
interact/mix with water. You know already that oil and water don't mix, right? Well, the fact
that lipids cannot interact well with water gives them many special properties. This group is also
the only group that is not built simply by combining smaller chemical subunits into long chains.
Lipids also include steroids and another type of molecule that you probably haven't heard about
before-- phospholipids. This last type of lipid is important in building cell membranes.
Proteins are an extremely diverse group of macromolecules. These molecules provide us with
pigment. They also enable cells to move, to have a specific shape, and to recognize material
around them. There are not many popular proteins that you would have heard about... the only
ones I am pretty sure you know something about are insulin, hemoglobin, and melanin (skin
pigment). Another protein is dystrophin, a protein in muscle that is affected in muscular
dystrophy. If you look over these examples, you might notice that they are items that can be
affected by genetic disorders (like sickle cell anemia, albinism, and MD). That is because all
that genes do is tell our cells what proteins to make. When we display the right set of proteins,
we are our unique selves. No two people display the same exact sets of proteins.
Nucleic acids are the macromolecules that make up our genetic code. You have heard of
DNA, well it stands for deoxyribonucleic acid. There is also another type of nucleic acid called
RNA... we'll get to that next week. But your genes are all made up of DNA, and the DNA
molecules are wound up within your chromosomes.
Cells are built as some of each macromolecule lies down in specific places. Membranes get
phospholipids and proteins. DNA is stuck in the nucleus of the cell. And so on. You will get
this information next week.
What do I mean by a "big" molecule versus a small molecule? Well, you saw an image of a
water molecule above. That's a small molecule. Another small (and very important in my dayto-day life!) molecule is caffeine. Here's what caffeine looks like:
Every ball in the diagram, whether it is a gray, blue, red, or white ball,
represents one atom. This molecule is a lot larger than a water molecule.
Water only had three atoms, while this one has 24 atoms. But this is still
considered a small molecule.
So what do I mean when I talk about a large molecule (a
macromolecule)? Well,
here's a protein. This is a
protein that you have in your saliva and that we
will study later this semester. It is called
amylase. This is a macromolecule, but certainly
not the largest macromolecule that we could
study. Many proteins are even larger than this
one!
There are certainly too many atoms to count in
this molecule. In order to fit it on the page, I had
to have every atom be a lot smaller than in the
original caffeine diagram above. Therefore, I
have included a miniature image of
caffeine here, so that you can compare its
size to the protein.
The 20 types of Amino Acids found in the
Human body
Essential – Must be provided by our food
Nonessential – Our cells can produce these
amino acids