BIO - Introduction to Biomolecules [LESSON]

Introduction to Biomolecules

Biomolecules (often called macromolecules) are the carbohydrates, fats, proteins, and nucleic acids that make up all living things. We will spend quite a bit of time exploring each one, but first, we will learn general vocabulary and the types of reactions that bind or break biomolecules.

Most large biological molecules are polymers, long chains made up of repeating molecular subunits, or building blocks, called monomers. If you think of a monomer as being like a bead, then you can think of a polymer as being like a necklace which is a series of beads strung together. All biomolecules except lipids (fats) have the ability to join monomers together indefinitely and form long chains or even more complex polymers.

Dehydration synthesis:

Large biological molecules often assemble via dehydration synthesis reactions, in which one monomer forms a covalent bond with another monomer (or a growing chain). This releases a water molecule in the process and is what gives the reaction its name. These are also called condensation reactions.

The image shows two glucose molecules next to each other.

In the dehydration synthesis reaction above, two monomers of glucose combine to form a single molecule of the sugar maltose. One of the glucose molecules loses an H and the other loses an OH group.  This creates a water molecule which is released as a new covalent bond forms between the two glucose molecules. As additional monomers join, the chain can get longer and longer to eventually form a polymer.

Hydrolysis:

Polymers are broken down into monomers via hydrolysis reactions, in which a bond is broken by the addition of a water molecule. During a hydrolysis reaction, a molecule composed of multiple subunits is split in two: one of the new molecules gains a hydrogen atom, while the other gains a hydroxyl (-OH) group, both of which are donated by water. This is the reverse of a dehydration synthesis reaction, and it releases a monomer that can be used in building a new polymer. For example, in the hydrolysis reaction below, a water molecule splits maltose to release two glucose monomers.

The image shows maltose, which is two glucose molecules linked to each other.

Interactive: Polymerization

Challenge: Build a polymer

  • Select one of the monomer types and add about 15 monomers by clicking anywhere in the Polymerization reaction chamber.

  • Click the play button to start the reaction.

  • Notice how the monomers of each type interact with each other. What type of creation forms these bonds? Dehydration synthesis

You can test your knowledge of this lesson with the Dehydration Synthesis/Hydrolysis Sorting practice below.

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