Notes: Macromolecules

Assortment of macromolecules

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There are 4 classes of large molecules that make up the majority of living things. They are called Macromolecules.  Since macromolecules are generally made up of many smaller molecules and atoms, they are referred to as polymers.  Polymers are made up of smaller units known as monomers.

The macromolecules of life are:

We will look at each to determine the make-up, functions and examples as found in living things.

Ever wonder where life's molecular building blocks come from? If so, take a look at the Molecular Logic Project's nifty concept map. The Molecular Logic Project's mission is to improve the ability of all students to understand fundamental biological phenomena in terms of the interactions of atoms and molecules.

Image of and link to a graphic organizer from the Molecular Logic Project.

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In order to gain a better understanding of macromolecules and the molecular building blocks that comprise them, you may want to visit and use MolviZ.Orgwhich contains a number of molecular visualization resources initiated and authored or managed by Eric Martz (University of Massachusetts, Amherst).

Screenshot and link to

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Carbon compounds are found in all living things and are called organic compounds. Several properties of carbon contribute to its versatility:


Inorganic compounds are those that do not contain carbon; many are also essential to life.  Water, nitrate and phosphate compounds are required, but are not organic. Exceptions to the 'carbon' rule are Carbon Dioxide and Carbon monoxide. They contain carbon, but are not considered organic.


Just to make sure you get the idea: Carbon (solid), Hydrogen (gas), Oxygen (gas), and Nitrogen (gas) are among the four most common elements found in living organisms (just remember CHON). These four elements are also notable for being the least massive (and having the lowest atomic number) in their group in the periodic table.


Carbohydrates - macromolecules composed of carbon, hydrogen and oxygen in a ratio of 1:2:1.     

Ex:  glucose, C6H12O6

Carbohydrates are sugars; sugars can be simple monomers, such as glucose or fructose, or complex polymers, such as starch.


Polysaccharides are large sugar molecules composed of many smaller units, linked together in complex arrangements.  Starch and cellulose (as depicted in the 3D model below), made by plants and glycogen found in animals are types of polysaccharides.  Starches and glycogen are used to store energy; cellulose is the structural component of cell walls.

Image and link to model of polysaccharide known as cellulose
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Disaccharides are sugar molecules with only two monomers; table sugar is an example of a disaccharide.  These types of sugars are generally used as a source of energy.


This is sucrose, a common disaccharide.

image of sucrose or Saccharose  

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Here's another representation of sucrose as well.

Image and link to a 3D model of sucrose.

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Monosaccharides are the monomer units of carbohydrates; they are glucose, fructose and galactose.

Representation of glucose and fructose

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Lipids are macromolecules composed of mostly carbon and hydrogen chains; primarily fats, waxes oils and steroids

Monomers (single) units of lipids are made of fatty acids attached to a glycerol molecule.  They usually combine in a ratio of 1 glycerol to 3 fatty acids. What you see below is ball and stick model of glycerol. Glycerol is a type of alcohol with a hydroxyl group on each of its three carbons.


Image of glycerol molecule

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Glycerol along with 3 fatty acids make a monomer of lipid.


Add a few things to glycerol (like fatty acids) and you have the ingredients for substances that are extremely useful to living things. For example, triglyceride is glyceride in which the glycerol is esterified with three fatty acids. You'll find it in stuff like vegetable oil and animal fats.


Image of and link to informationa about triglyceride

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Examples of lipids are fats, oils, waxes and steroids. Lipids are not soluble in water. The fatty acids can be saturated or unsaturated.

Lipids have a lot of important jobs in living things. Some of these are:

They form waterproofing (waxes) act as

To learn more about lipids, click here to visit J. Stein Carter's webpage devoted to the topic.

Screenshot of and link to a webpage about lipids


Nucleic acids - macromolecules containing hydrogen, oxygen, nitrogen, carbon and phosphorus and are associated with organism's genetic code.

Monomer (single) units of nucleic acids are called nucleotides.  One nucleotide consists of a 5-carbon sugar, a phosphate group and a nitrogen base.


Two examples of nucleic acids are deoxyribonucleic acid (DNA), and ribonucleic acid (RNA).  

Image depicting how the process of transcription is carried out by RNA polymerase, using DNA as a template to produce RNA

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The function of nucleic acids is to store and transmit genetic information (chemical instructions about how living things should form and operate).  You will learn much more about nucleic acids in a future unit of study.


Proteins - macromolecules containing carbon, hydrogen, oxygen and nitrogen; proteins are considered the building blocks of tissue

Monomer units of proteins are called amino acids.
Amino acids can link together and form molecules called proteins.

Proteins perform several critical jobs in cells. Functions of proteins include:

 One of the most important types of proteins is called an enzyme:

Enzymes can be synthetic (they can build up) or hydrolytic (they can breakdown or digest). They are very specific for their substrates. Most end in -ase .



Enzymes must have the best environmental conditions to operate most efficiently. This is called their optimum enzyme activity.

The three (3) conditions that limit enzyme activity are:

Click here to visit Chem4Kids and read more about enzymes.