What is a Macromolecule?

When you were younger, you probably enjoyed building things with blocks or stringing beads into a necklace. You were using small units to make a larger object using these small units over and over until you got the bigger item you wanted to construct.

A macromolecule is constructed in exactly the same way. The term macromolecule means very big molecule. As you know, a molecule is a substance that is made up of more than one atom. The prefix macro- means 'large,' and it is an antonym of the prefix micro- which means 'very small.' Macromolecules are huge! They are made up of 10,000 or more atoms!

Another term for a macromolecule is a polymer. You probably know from math classes that the prefix poly- means 'many,' as in a polygon, or a figure with many sides. Because macromolecules are made of many building blocks, called monomers, you can see why these terms are synonymous. Think of a monomer as being a brick, and a polymer, or macromolecule, as being the whole brick wall composed of the building blocks. The brick wall is composed of smaller units (the bricks) just as a macromolecule is composed of monomer 'building blocks.'

Types of Macromolecules

You may be wondering if you've ever encountered a macromolecule. Well, wonder no longer! All around you right now, you are surrounded by them! You may be sitting on a chair that is upholstered with a man-made fabric. Your laptop is mostly composed of plastics. Plastics are polymers made from petroleum products. The sandwich you had for lunch was made up of macromolecules - the starch in the bread is one, the ham, which is mostly protein, is another, and the lettuce and tomatoes contain complex carbohydrates called cellulose. Let's not forget the mayo—yes, another one! Mayonnaise contains fats, which are macromolecules. These macromolecules are made by organisms.

All of the trillions of cells that make up your body contain biological polymers, or macromolecules. Your cells are made up of proteins, lipids, carbohydrates, and nucleic acids.

Macromolecules Used in Industry

In addition to the very important biologic macromolecules (proteins, lipids, polysaccharides, and nucleic acids), there are three major groups of macromolecules that are important in industry. These are elastomers, fibers, and plastics.

Elastomers are macromolecules that are stretchy and very flexible. This elastic property allows these materials to be used in products like elastic waistbands and hair bands. These products can be stretched, but they return to their original structure. A natural, non-manmade, elastomer is rubber.

You probably wear fiber macromolecules. Polyester, nylon, and acrylic fibers are used in everything from shoes to belts to shirts and blouses. Fiber macromolecules are string-like, which when woven together are very durable. Natural fibers include silk, cotton, wool, and wood.

What did we do before plastics were invented? So many of the materials we use every day are made of these macromolecules. There are many types of plastics, but all of them are made through a process called polymerization, the joining of monomer units to form the plastic polymers. Until recently, all plastics were made from petroleum products.

There is a new group of plastics, called bioplastics, which have the advantage of using renewable resources for their manufacturing. Bioplastics, unlike traditional plastics, can break down, or degrade, which make them safer for the environment. Environmentally conscious individuals take care to recycle plastic materials. There are no naturally occurring plastics.

Examples

The biologic macromolecules are essential to life. All living things are made up of just four macromolecules: proteins, lipids, polysaccharides, and nucleic acids.

Proteins are macromolecules made up of amino acid building blocks. There are thousands of proteins in organisms, and many are made up of several hundred amino acid monomers. Check out the following table for some examples of proteins in your body (see video).

Lipids are macromolecules that are made up of long chains of fatty acids, or carbon rings. Important lipids in your body include cholesterol, steroid hormones, triglycerides, and phospholipids. These lipids range in function from hormones to cell membrane components to fat storage units.