Monomers & Polymers - Online Tutor, Practice Problems & Exam Prep

Monomers are the individual building blocks that link together to form polymers, with "mono" meaning one and "poly" meaning many. Carbohydrates, proteins, and nucleic acids utilize consistent monomers—monosaccharides, amino acids, and nucleotides, respectively—while lipids do not. To build polymers, cells perform dehydration synthesis, forming covalent bonds and releasing water. Conversely, hydrolysis breaks down polymers into monomers by adding water to cleave 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 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. Therefore, polymers are defined as long chains of many monomers linked together. The monomers, those individual building blocks that are used to build polymers, will vary depending on the type of biomolecule polymer 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 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.

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 these individual separate building blocks. Because these are single individual building blocks that are separate from one another, we refer to these as monomers. If we were to link all of these monomers together into a long chain, then we have ourselves a polymer. This whole thing is a polymer, and the individual pieces we see here are the monomers. As mentioned earlier, monomers will vary depending on the type of biomolecule polymer, and it's only carbohydrates, proteins, and nucleic acids that use consistent monomers, so those are the ones we're going to focus on in this key. Lipids do not use consistent monomers, so we'll discuss lipids later.

If we look at this key on the left-hand side, notice that for carbohydrates, all of these gray monomer building blocks are monosaccharides. Moving forward in our course, we're going to represent those building blocks, those monosaccharides, as bluish hexagons. For proteins, on the other hand, these gray building blocks, these monomers, are amino acids, which we will represent as circles moving forward in our course. For nucleic acids, the monomers, these pieces we see here, are going to be nucleotides, which we will represent with shapes that look like this. The main point here is that these monomers will vary depending on the type of biomolecule polymer they are building, whether they are building carbohydrates, proteins, or nucleic acids.

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. A cell needs to perform a dehydration synthesis reaction if it wants to build a polymer. 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, with the root 'lysis' meaning cleaving and breaking things down, will cleave covalent bonds between the monomers and release the monomers as separate pieces by breaking down the polymer. Once again, dehydration synthesis is all about building a polymer, whereas hydrolysis focuses on cleaving or breaking down the polymer.

Let's take a look at our image 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 this reaction, the hydroxyl group (OH group) of one monomer interacts with a hydrogen on another monomer, causing OH and H to release a water molecule. You can see the blue OH here is coming from this OH, and the yellow H is coming from this hydrogen. When water is released, as we see here, the molecules are being dehydrated. In the process, it's synthesizing something; it is building a polymer and that's how the monomers are joined together covalently, as we can see.

If the cell wanted to perform the opposite and break down this polymer into its separate individual monomers, it would need the backwards reaction to release those 2 monomers. Recall that this is called hydrolysis. The 'lysis' part is about cleaving and breaking things down. This bond here can be cleaved or broken by using water, and that's what the 'hydro' prefix indicates in hydrolysis. Notice that a water molecule is needed in the process, which will 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, it will 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.

• 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.

_________ bonds are formed between monomers to form a polymer. 

a) Ionic bonds.

b) Covalent bonds.

c) Hydrogen bonds.

d) Hydrophobic bonds.

e).  Nuclear bonds.

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

Here’s what students ask on this topic:

What are monomers and polymers, and how do they differ?

Monomers are individual building blocks that can be repetitively linked together to form polymers. The term 'monomer' comes from 'mono,' meaning one or singular. Polymers, on the other hand, are long chains of many monomers linked together, with 'poly' meaning many. For example, in carbohydrates, the monomers are monosaccharides, in proteins, they are amino acids, and in nucleic acids, they are nucleotides. Lipids are an exception as they do not use consistent monomers to form polymers. Understanding the distinction between monomers and polymers is crucial for grasping the structure and function of various biomolecules.

What is dehydration synthesis, and how does it build polymers?

Dehydration synthesis is a chemical reaction that forms covalent bonds between monomers to build polymers. During this process, a hydroxyl group (OH) from one monomer interacts with a hydrogen (H) from another monomer, releasing a water molecule (H₂O). This reaction is called 'dehydration' because it involves the loss of water, and 'synthesis' because it builds a larger molecule. For example, when two glucose molecules undergo dehydration synthesis, they form a disaccharide and release water. This process is essential for forming complex biomolecules like carbohydrates, proteins, and nucleic acids.

What is hydrolysis, and how does it break down polymers?

Hydrolysis is a chemical reaction that breaks down polymers into their monomer components by adding water. The term 'hydrolysis' comes from 'hydro,' meaning water, and 'lysis,' meaning to break. During hydrolysis, a water molecule is added to the polymer, cleaving the covalent bonds between monomers. For example, when a disaccharide undergoes hydrolysis, it splits into two monosaccharides with the addition of water. This reaction is crucial for cellular processes that require the breakdown of complex molecules into simpler ones for energy and other functions.

What are the consistent monomers used to form carbohydrates, proteins, and nucleic acids?

Carbohydrates, proteins, and nucleic acids each use specific monomers to form their polymers. Carbohydrates are made up of monosaccharides, such as glucose. Proteins are composed of amino acids, which are linked together by peptide bonds. Nucleic acids, like DNA and RNA, are formed from nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. These consistent monomers are essential for the structure and function of their respective biomolecules, enabling them to perform various biological roles.

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 carbohydrates, proteins, and nucleic acids. Lipids are primarily composed of fatty acids and glycerol, but they do not form long chains of repeating units like other biomolecules. Instead, they form complex structures such as triglycerides, phospholipids, and steroids. These structures are essential for functions like energy storage, cell membrane formation, and signaling, but they do not rely on a repetitive monomer-polymer relationship.