Dimer: Definition & Formation

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  • 0:00 What Are Dimers?
  • 1:30 Dimer Formation
  • 3:51 Types of Dimers
  • 5:00 Lesson Summary
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Lesson Transcript
Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

In this lesson, we'll cover the formation of different types of dimers. You'll learn how to recognize a variety of dimers and the useful functions they perform for us. Test your knowledge afterward with a short quiz.

What Are Dimers?

Did you know that dimers are found in many substances from sugars to chemicals and proteins? How about we learn about these compounds to understand why they're so popular?

Dimers are oligomers composed of two monomers that are similar in structure and joined by a chemical bond. A great analogy is to think of dimers as a city that has a bridge connecting two small towns together. I know, you may be wondering, olio-who? Oligomers are molecular complexes made of little units called monomers. Just think of a molecular complex as a big chemical glob that has a bunch of parts to it. A great example of a type of oligomer is hemoglobin which is found in red blood cells in our blood. As you can see, hemoglobin has four monomers linked to make one huge glob, or oligomer.

Diagram 1: Oligomer Structure of Hemoglobin
hemoglobin

Depending on how many monomers you have in one oligomer, the name of the structure will change. So three monomers linked would be an oligomer named trimer. Four monomers linked together would be an oligomer named tetramer. But wait, what is a monomer? A monomer is a molecule that loves to bind chemically with other molecules. Think of a monomer as a small tough guy that loves to network and build a web of friends. If we put all of this together, a dimer is a type of oligomer. But monomers are the building blocks for dimers and all oligomers.

Dimer Formation

Think back to our first example. Would hemoglobin be called a dimer? Let's explore the structure of dimers and then go back to answering that question. As we learned earlier, dimers contain monomers linked together. To break this down further, take a look at the word dimer. The prefix 'di-' means two. The suffix '-mer' means parts. Thus a dimer would be two parts. In this case those parts are monomers. Here you see black blocks symbolizing the link to be formed between both monomer units.

Diagram 3: Simple Mechanism of How a Dimer Is Formed
dimer

This link is called a bond. For dimers, this bond can be strong or weak. It can also be classified into two categories: non-covalent or covalent. Non-covalent dimers, as the name suggests, use non-covalent bonds to link monomers together. A non-covalent bond is any chemical bond that does not involve sharing of electrons. These bonds form when molecules want to link up but don't want to share their electrons to do so. For dimers, a great example of a non-covalent dimer is a hydrogen bond. Here's an example of a non-covalent dimer using hydrogen bonding. The individual monomer subunits linked together are circled.

Diagram 4: Chemical Structure of Acetic Acid Cyclic Dimer
cyclic dimer

Covalent dimers are the exact opposite. These are dimers that use covalent bonds to link monomers together. A covalent bond involves the sharing of electrons. These molecules are happy to share electrons with one another in order to link up. A great example of a covalent dimer is a diatomic gas. Think of hydrogen gas, nitrogen gas, and oxygen gas. Hydrogen, nitrogen, and oxygen atoms love sharing electrons to form a covalent bond and make a diatomic molecule.

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