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Monomers and Polymers

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Monomers and Polymers

Ever wondered how your body is able to digest, store information, or manipulate everything? Macromolecules in your body carry out vital functions needed by cells and are essential to these processes. Macromolecules consist of joined monomers that form polymers.

Definition of a monomer

Monomers are small molecules that form larger molecules called polymers.

  • Mono- means 'one' or 'single', so monomers are single, individual units.

  • These can be one single molecule or a combination of units.

  • It is helpful to remember that monomers are simple molecules and the smallest repeating units in polymers.

Definition of a polymer

Polymers are molecules made from monomers that join together.

  • Polymers are very large molecules made of single, similar repeating units (monomers).

  • Poly- means 'many' or 'multi-', meaning that a polymer consists of many monomers.

Differences between monomers and polymers

These are the differences that set apart the smaller molecules - monomers, and larger molecules - polymers:
Differences

Monomers

Polymers

SIZE

Small, simple molecules

Large, complex molecules

BUILDING BLOCKS

Can have a combination of units.

Monomers are small units that are the building blocks of polymers.

Contain monomers, single repeating units, as their building blocks.

What are the three categories of monomers?

There are three categories of monomers: monosaccharides, amino acids, and nucleotides.

1. Monosaccharides

When monosaccharides join together, they form polymers that are polysaccharides (complex carbohydrates). For this reason, monosaccharides are monomers of complex carbohydrates, such as starch and cellulose.

Monosaccharides are organic molecules. They contain carbon, hydrogen, and oxygen atoms. Examples include glucose, fructose, galactose, ribose (found in RNA), and deoxyribose (found in DNA).

Figure 1 shows the ring structures of each of synthesis important monosaccharide.

Figure 1

2. Amino acids

Amino acids are the building blocks of polypeptides (proteins). For this reason, amino acids are monomers of proteins, such as haemoglobin and insulin.

Amino acids are also organic molecules. They contain carbon and hydrogen, but oxygen and nitrogen as well.

Amino acids consist of:

  • a central carbon atom

  • to amino group

  • a carboxyl group and

  • one organic R group that is unique to each amino acid.

Examples of amino acids include alanine and valine.

Figure 2

3. Nucleotides

Nucleotides join together to form polynucleotides (nucleic acids). Therefore, nucleotides are monomers of nucleic acids (DNA and RNA).

Nucleotides are also organic molecules, as they contain carbon and hydrogen. They also contain oxygen, hydrogen, and one to three phosphates.

Nucleotides have a pentose (a five-carbon sugar) as a base, which is attached to a nitrogenous base and a phosphate group.

Nucleotides in DNA have deoxyribose as a base, while the ones in RNA have ribose.

Figure 3 illustrates a simplified structure of a nucleotide. Note the phosphodiester bond on the third carbon atom, linking it to the next nucleotide in the chain.

Figure 3

Figure 3. Simplified structure of a nucleotide with a phosphodiester bond linking it to the next nucleotide.

Source: commons.wikimedia.org

What are the three categories of polymers?

Polymers are divided into three groups: polysaccharides, polypeptides, and polynucleotides.

They all have one clear property in common: Their long chains consist of repeating similar units - monomer.

1. Polysaccharides (Complex carbohydrates)

Polysaccharides are polymers composed of multiple monosaccharides. Complex carbohydrates are polysaccharides: starch, glycogen, and cellulose. All three are composed of repeating units of glucose . Figure 4 shows the complex branched structure of polysaccharide glycogen. Individual repeating circles are glucose molecules.Figure 4

2. Polypeptides (proteins)

Polypeptides are composed of monomers that are amino acids. Proteins are polypeptides. Examples of polypeptides include hemoglobin , insulin and keratin . Take a look at Figure 5, which illustrates the primary structure of a protein, a polypeptide. Similar to the image above, individual circles represent amino acids.

Figure 5

3. Polynucleotides (Nucleic Acids)

Polynucleotides are composed of monomers that are nucleotides. Nucleic acids are polynucleotides. Biologically, the most essential polynucleotides are DNA and RNA .

Let's study the image below. It shows one part of the DNA structure. Can you spot individual nucleotides?

Figure 6
MonomersPolymers
Monosaccharides Polysaccharides (complex carbohydrates)
Amino acidsPolypeptides (proteins)
NucleotidesPolynucleotides (nucleic acids)

There are four major biological macromolecules: carbohydrates, proteins, nucleic acids, and lipids.

So what about lipids? Why are lipids not mentioned here? Lipids are not polymers, and fatty acids and glycerols are not monomers. Yes, lipids are composed of smaller units (a combination of fatty acids and glycerol), but these units do not form repetitive chains. As a result, unlike polymers, lipids contain a chain of non-similar units.

How do monomers join together to form polymers?

Monomers bond together with chemical bonds to form polymers. This process is called polymerization.

Two different reactions form and break polymers: condensation reaction and hydrolysis reaction.

Let's have a look at what these two reactions look like on a diagram. Figure 7 illustrates a simplified diagram of how condensation and hydrolysis reactions make and break polymers. Note the addition and removal of water molecules.

Figure 7

1. Condensation reaction

'Dehydration synthesis' is a synonym for condensation reaction. 'Dehydration' literally means the removal of water (or loss of water - think what happens when you say you are dehydrated). 'Synthesis' in biology refers to the creation of compounds (biological molecules).

As seen in the diagram above (a), monomers need to join together for a polymer to form. Monomers join with chemical bonds called covalent bonds. These bonds form with the help of water, which is removed during the reaction (it is "lost").

Three covalent bonds form between various monomers: glycosidic, peptide, and phosphodiester bonds.

As a result, we can conclude that:

  • Condensation of monosaccharides results in the formation of polysaccharides. The bond that forms between monosaccharides is a glycosidic bond.

  • Condensation of amino acids results in the formation of polypeptides. The bond that forms between amino acids is a peptide bond.

  • Condensation of nucleotides results in the formation of polynucleotides. The bond that forms between nucleotides is a phosphodiester bond.

2. Hydrolysis reaction

Above, in Figure 7 (b), you can see that polymers are broken down during the reaction of hydrolysis.

Hydrolysis is the opposite of condensation. Here, the covalent bonds between monomers are broken, not created, with the help of water. That is why we say that water is added to this reaction.

Similar to condensation, we can conclude that:

  • Hydrolysis of polysaccharides results in the breaking down of the molecule into its monomers: monosaccharides. The covalent glycosidic bonds between monosaccharides break down.

  • Hydrolysis of polypeptides results in the breaking down of the molecule into its monomers: amino acids. The covalent peptide bonds between amino acids break down.

  • Hydrolysis of polynucleotides results in the breaking down of the molecule into its monomers: nucleotides. The covalent phosphodiester bonds between nucleotides break down.

As already mentioned, lipids are not polymers. However, they are formed during condensation and broken down during hydrolysis. Therefore, condensation of fatty acids and glycerol results in the formation of lipids. Equally, hydrolysis of lipids results in the breaking down of lipids into fatty acids and glycerol.

Monomers and Polymers - Key takeaways

  • Monomers are simple molecules and the smallest repeating units in polymers.

  • Polymers are very large molecules (macromolecules) that are made from single repeating units (monomers).
  • There are three categories of monomers: monosaccharides, amino acids, and nucleotides.
  • There are three categories of polymers: polysaccharides, polypeptides, and polynucleotides.
  • Condensation is a reaction during which covalent bonds form between monomers that join to form polymers. Covalent bonds that form between various monomers during condensation are glycosidic, peptide, and phosphodiester bonds.
  • Hydrolysis is a reaction during which covalent bonds between monomers break down, which results in the breaking down of polymers into monomers.

Frequently Asked Questions about Monomers and Polymers

Differences between monomers and polymers: 

  • Size: Monomers are small, simple molecules, while polymers are large, complex molecules. 
  • Building blocks: Monomers can have a combination of units. Monomers are small units that are the building blocks of polymers. Polymers have monomers, single repeating units, as their building blocks.

Polymers are built of monomers. Monomers are the building blocks of all polymers.

The examples of the relationship between monomers and polymers: 

  • Polysaccharides are polymers and their monomers are called monosaccharides. Complex carbohydrates are polysaccharides.
  • Polypeptides are polymers and their monomers are amino acids. Proteins are polypeptides.
  • Polynucleotides are polymers and their monomers are nucleotides. Nucleic acids are polynucleotides. 

Monomers of carbohydrates are monosaccharides.

Monomers of proteins are amino acids.

Monomers of nucleic acids are nucleotides.

Final Monomers and Polymers Quiz

Question

What is the definition of a monomer?

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Answer

Monomers are small molecules, single repeating units, in polymers. 

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Question

What is the definition of a polymer?

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Answer

Polymers are very large molecules made of monomers that are joined together with chemical bonds.

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Question

What is the relationship between monomers and polymers?

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Answer

Monomers are the building blocks of polymers. They are joined together with chemical bonds to form polymers. Polymers consist of monomers.

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Question

What are the three categories of monomers? They are m_______, a_____ a_____, and n_______.

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Answer

monosaccharides, amino acids, and nucleotides.

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Question

What are monosaccharides monomers of?

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Answer

Polysaccharides (carbohydrates). 

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Question

What are amino acids monomers of?

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Answer

Polypeptides (proteins). 

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Question

What are nucleotides monomers of?

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Answer

Polynucleotides (nucleic acids).

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Question

What are the three categories of polymer?

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Answer

Polysaccharides, polypeptides, and polynucleotides.

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Question

What are the biologically most important polynucleotides?

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Answer

DNA and RNA

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Question

What is the process of monomers joining together to form polymers called?

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Answer

Polymerisation. 

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Question

What are the two different reactions in charge of making and breaking polymers?

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Answer

Condensation and hydrolysis reactions

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Question

What happens during condensation? Fill in the gaps: 

During condensation, c_______ form between m________, which then join together to form p__________. Water is r________.

Show answer

Answer

During condensation, covalent bonds form between monomers, which then join together to form polymers. Water is removed.


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Question

What are the different covalent bonds between monomers called?

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Answer

Glycosidic, peptide, and phosphodiester bonds.

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Question

What is the covalent bond in lipids called?

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Answer

Ester bond. 

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Question

Which monomers bond together with a peptide bond?

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Answer

Amino acids

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Question

What happens during hydrolysis? Fill in the gaps:

During hydrolysis, c_________ bonds between monomers b______, and a polymer is b_____ d_____ into m________. Water is a_______.

Show answer

Answer

During hydrolysis, covalent bonds between monomers break, and a polymer is broken down into monomers. Water is added.


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Question

It is said that hydrolysis is the opposite of condensation. Why is that?

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Answer

Hydrolysis is the opposite reaction to condensation because, during hydrolysis, polymers are broken down into monomers, while during condensation monomers are joined together to form polymers. Covalent bonds are broken during hydrolysis and created during condensation. 


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Question

What is the definition of condensation in biology?

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Answer

Condensation is a chemical reaction during which monomers (small molecules) covalently bond to form polymers (large molecules or macromolecules).


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Question

What happens with water during condensation?

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Answer

Water is released (lost) during condensation.

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Question

What happens during the condensation of galactose and glucose?

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Answer

Lactose forms and water is lost.

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Question

What polymers form during a condensation reaction of monosaccharides?

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Answer

Polysaccharides

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Question

What is the name of the covalent bond that forms between monosaccharides during condensation?

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Answer

A glycosidic bond

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Question

In one condensation reaction, the result is a polymer called a polypeptide. What are its monomers called?


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Answer

Amino acids

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Question

What is the name of the covalent bond that forms between amino acids during condensation? 


Show answer

Answer

A peptide bond

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Question

What polymers form during a condensation reaction of nucleotides?

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Answer

Polynucleotides

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Question

What is the name of the covalent bond that forms between nucleotides during condensation?

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Answer

A phosphodiester bond

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Question

Even though they are not polymers, and their building blocks fatty acids and glycerol are not monomers, lipids form in a condensation reaction.

True or False


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Answer

True. Lipids still form during a condensation reaction of fatty acids and glycerol. 

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Question

What is the purpose of condensation?

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Answer

The purpose of a condensation reaction is the creation of polymers that are large, essential biological molecules.

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Question

Why is the condensation of nucleotides significant?

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Answer

During condensation of nucleotides, the nucleic acids DNA and RNA form. They are crucial for all living matter as they carry genetic material. Without condensation, this vital function would not be possible. 


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Question

Why is the condensation of fatty acids and glycerol significant? Fill in the gaps.

The condensation of fatty acids and glycerol is significant because _____ form as a result. ______ are essential energy________ molecules, building blocks of _____ _________ and providers of insulation and _________. Without condensation, these vital functions would not be possible.

Show answer

Answer

The condensation of fatty acids and glycerol is significant because lipids form as a result. Lipids are essential energy storage molecules, building blocks of cell membranes and providers of insulation and protection. Without condensation, these vital functions would not be possible.

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Question

What is the definition of hydrolysis?

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Answer

Hydrolysis is a chemical reaction during which polymers (large molecules) are broken down into monomers (small molecules).


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Question

What happens with water during hydrolysis?

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Answer

Water is added during hydrolysis.

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Question

What happens during hydrolysis of lactose?

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Answer

The hydrolysis reaction breaks lactose down by breaking glycosidic bonds between galactose and glucose. Water is added to the reaction.

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Question

What is the name of the covalent bond that breaks between monosaccharides during hydrolysis?

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Answer

A glycosidic bond

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Question

What polymers are broken down during the hydrolysis in which the result is amino acids?

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Answer

Polypeptides

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Question

What happens during hydrolysis of polynucleotides? Fill in the gaps.
During the hydrolysis reaction of polynucleotides, they are _____  ______ into monomers ___________. Water is added, and covalent bonds called ____________ ________ between nucleotides are _______.

Show answer

Answer

During the hydrolysis reaction of polynucleotides, they are broken down into monomer nucleotides. Water is added, and covalent bonds called phosphodiester bonds between nucleotides are broken.


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Question

Lipids do not go through hydrolysis reactions as they are not polymers. 

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Answer

False. 


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Question

What is the purpose of hydrolysis?

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Answer

The purpose of hydrolysis reaction is the breaking down of polymers into monomers or small molecules. This is important for the normal functioning of cells, as they absorb small molecules, which give them energy.

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Question

What happens in the digestive tract after we eat?

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Answer

The food is broken down into smaller molecules during hydrolysis in the digestive tract. Proteins that help catalyse hydrolysis are enzymes.

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Question

Why are living organisms dependent on both condensation and hydrolysis?

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Answer

Because the much-needed energy is stored in macromolecules that are formed during condensation, and it is released during hydrolysis.


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Question

What are the proteins that help hydrolysis called?

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Answer

Enzymes.

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