Monomers & Polymers: Videos & Practice Problems

Monomers are the individual building blocks that link together to form polymers, which are long chains of these monomers. Carbohydrates, proteins, and nucleic acids utilize specific monomers—monosaccharides, amino acids, and nucleotides, respectively—while lipids do not have a consistent monomer. To build polymers, cells perform dehydration synthesis, forming covalent bonds and releasing water. Conversely, hydrolysis reactions break down polymers into monomers by adding water to cleave the bonds. Understanding these processes is crucial for grasping biomolecular structures and functions.

Monomers & Polymers

In this video we're going to introduce the two terms, monomers and polymers. Monomers, with the mono prefix, are going to be single individual building blocks that can be repetitively linked together to form polymers. The root mono actually means 1 or singular, whereas the root poly in polymers means many. Thus, polymers are defined as long chains of many monomers that are linked together. The monomers, those individual building blocks that are used to build polymers, will actually vary depending on the type of biomolecule polymer that they're building. It's important to also note that carbohydrates, proteins, and nucleic acids all use consistent monomers to form their polymers. However, lipids are a little bit different because they do not use a consistent monomer to build polymers, and we'll get to talk more about these lipids later in our course. But for now, let's focus on the monomers and the polymers.

So if we take a look at our example image down below, we can focus on the monomers and the polymers. I'm going to direct you to this image on the right-hand side, which shows you these individual separate building blocks. Because these are single individual building blocks that are separate from one another, we refer to these as monomers. And then, of course, if we were to link all of these monomers together into a long chain of many monomers linked, then we have ourselves a polymer. This whole thing is a polymer, and these individual pieces that we see over here are the monomers.

As we mentioned above, monomers are going to vary depending on the type of biomolecule polymer, and really it's only the carbohydrates, proteins, and nucleic acids that use consistent monomers, so those are the ones that we're going to focus on over here in this key. The lipids, they don't use consistent monomers, so we'll talk about the lipids later. But if we take a look at this key over here on the left-hand side, notice that for carbohydrates all of these little gray monomer building blocks that we see over here are really going to be monosaccharides. Moving forward in our course, we're going to represent those building blocks, those monosaccharides as these bluish hexagons. For proteins, on the other hand, these gray building blocks that we see over here, these monomers would actually be amino acids, and those amino acids moving forward in our course, we're going to represent them as these circles. For nucleic acids, the monomers, these pieces that we see here are really going to be nucleotides, which moving forward in our course we're going to represent with shapes that look like this.

The real main point here is that these monomers are going to vary. What these building blocks are, they'll vary depending on the type of biomolecule polymer that they're building, whether they're building carbohydrates, proteins, or nucleic acids. Once again, we'll get to talk more about monomers and polymers moving forward in our course and this is just the introduction. So I'll see you all in our next video.

Building & Breaking-Down Polymers

In this video, we're going to talk about building and breaking down polymers. If a cell wants to build a polymer, it needs to perform a dehydration synthesis reaction. As its name implies with the synthesis part here, dehydration synthesis reactions form covalent bonds to link individual separate monomers together and begin to build a polymer. You can see that the synthesis here is all about forming and building a polymer. On the other hand, if a cell wants to break down a polymer into its small individual pieces, it needs to perform a hydrolysis reaction. Dehydration synthesis and hydrolysis reactions are opposites of one another. Hydrolysis has the root lysis in it, which is all about cleaving and breaking things down. Hydrolysis cleaves covalent bonds between the monomers and releases the monomers as separate pieces by breaking down the polymer. Once again, dehydration synthesis is all about building a polymer, whereas hydrolysis is all about cleaving or breaking down the polymer.

Let's take a look at our image down below to get a better understanding of the formation and breakdown of polymers. It's important to note that on the left-hand side of our image, we have 2 separate monomers, and on the right-hand side of our image, those monomers are now joined together covalently, starting to build a polymer. Of course, if we want to join together 2 separate monomers and begin to build a polymer, we're going to need a dehydration synthesis reaction. In the dehydration synthesis reaction, the hydroxyl group (OH) of one monomer interacts with a hydrogen (H) on another monomer, and OH and H release a water molecule. You can see the blue O here is coming from this OH and the yellow H is coming from this hydrogen. When water is released, as we see here, it dehydrates the molecule. The molecules are losing a water molecule, so the water molecules are being dehydrated, and in the process, it's synthesizing something. It is building a polymer, and that's how the monomers are joined together covalently here, as we can see.

If the cell wanted to do the opposite and break down this polymer into its separate individual monomers, it would need the backward reaction to release those 2 monomers, and recall that this is called hydrolysis. Once again, the lysis part is all about cleaving and breaking things down. This bond here can be cleaved or broken by using water, which is what the hydro prefix is for in front of hydrolysis. It's saying water is needed to cleave or break it down. A water molecule is going to be added to the process, and it's going to split the molecule in half. The biggest takeaway here is that if a cell needs to build a polymer, it will perform a dehydration synthesis reaction. If the cell needs to break down a polymer, then it's going to perform a hydrolysis reaction.

That concludes our introduction to this concept, and we'll be able to get practice applying this throughout our course as we move forward. So, I'll see you all in our next video.

Which of the following statements concerning dehydration reactions and hydrolysis is correct?

• A. Dehydration reactions allow solutions to evaporate; hydrolysis reactions dissolve solutes.
• B. Dehydration reactions and hydrolysis reactions assemble polymers from monomers.
• C. Hydrolysis reactions create polymers from monomers; and dehydration reactions create monomers from polymers.
• D. Dehydration reactions create polymers from monomers; hydrolysis reactions break down polymers.

Answer: (D)

_________ bonds are formed between monomers to form a polymer.

• A. Ionic bonds.
• B. Covalent bonds.
• C. Hydrogen bonds.
• D. Hydrophobic bonds.
• E. Nuclear bonds.

Answer: (B)

Here’s what students ask on this topic:

What are monomers and polymers in biology?

Monomers are single, individual building blocks that can repetitively link together to form polymers. The term 'monomer' comes from the root 'mono,' meaning one or singular. Polymers, on the other hand, are long chains of many monomers linked together. The term 'polymer' comes from the root 'poly,' meaning many. In biological systems, carbohydrates, proteins, and nucleic acids use consistent monomers—monosaccharides, amino acids, and nucleotides, respectively—to form their polymers. Lipids are an exception as they do not use consistent monomers to build polymers. Understanding the relationship between monomers and polymers is crucial for grasping the structure and function of biomolecules.

How are polymers formed and broken down in cells?

Polymers are formed in cells through a process called dehydration synthesis. During this reaction, covalent bonds are formed between individual monomers, and a water molecule is released. The term 'dehydration' refers to the loss of water, and 'synthesis' refers to the creation of a new bond. Conversely, polymers are broken down into monomers through hydrolysis. In this process, water is added to cleave the covalent bonds between monomers. The term 'hydrolysis' combines 'hydro,' meaning water, and 'lysis,' meaning to break down. These processes are essential for the dynamic regulation of biomolecular structures and functions in living organisms.

What are the monomers of carbohydrates, proteins, and nucleic acids?

The monomers of carbohydrates are monosaccharides, which are simple sugars like glucose. For proteins, the monomers are amino acids, which are organic compounds containing both an amino group and a carboxyl group. Nucleic acids, such as DNA and RNA, are composed of nucleotide monomers. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. These specific monomers link together to form the respective polymers: polysaccharides for carbohydrates, polypeptides for proteins, and polynucleotides for nucleic acids.

What is the difference between dehydration synthesis and hydrolysis?

Dehydration synthesis and hydrolysis are opposite biochemical reactions. Dehydration synthesis involves the formation of covalent bonds between monomers, resulting in the release of a water molecule. This process builds polymers from monomers. In contrast, hydrolysis involves the addition of a water molecule to break covalent bonds within a polymer, resulting in the release of individual monomers. Dehydration synthesis is essential for constructing complex biomolecules, while hydrolysis is crucial for breaking them down into simpler units for various cellular functions.

Why don't lipids use consistent monomers to form polymers?

Lipids do not use consistent monomers to form polymers because their structure and function differ significantly from other biomolecules like carbohydrates, proteins, and nucleic acids. Lipids are primarily composed of fatty acids and glycerol, but these components do not form long, repetitive chains like the monomers of other biomolecules. Instead, lipids are assembled into complex structures such as triglycerides, phospholipids, and steroids, which serve various roles in energy storage, membrane structure, and signaling. This structural diversity allows lipids to perform a wide range of biological functions.