Properties of Macromolecules - Online Tutor, Practice Problems & Exam Prep

Macromolecules exhibit key properties such as polymerization, where monomers like amino acids and monosaccharides combine through condensation reactions, releasing water. Stereoisomers, which are mirror images of molecules due to asymmetric carbon atoms, play a crucial role in biological functions, as only specific forms are utilized, like L-amino acids in proteins. Non-covalent bonds, though weak individually, become strong collectively, influencing macromolecule conformation and interactions, essential for functions in multi-protein complexes.

Polymerization

Hi. In this video, we're going to be talking about the properties of macromolecules. So the first property that I want to talk about is macromolecule polymerization. What is polymerization? Well, it's just a fancy term that allows for the sequential formation of large structures from individual subunits. Linear polymerization forms the structures of polysaccharides, nucleic acids, and proteins, but it does not allow for the formation of lipids. Lipids occur through a different manner, which we're not going to talk about here. So just realize when we talk about polymerization, we're not talking about lipids.

How does polymerization work? It occurs through a main reaction called a condensation reaction, which forms the bonds between monomers. So what are monomers? They're little subunits. They're either the individual amino acid or the individual monosaccharide that can form these larger structures. How do they form? They form through H⁺ and an OH^- groups on individual subunits, when those react, they release water. And so, repetition of these condensation reactions adds more monomers and forms these really large complex structures.

If we just take a second to look at a condensation reaction really quickly, you can see here we have 2 amino acids. How do we know they're amino acids? Anyone know? Okay. We know they're amino acids because they have the amino group, they have an R group, and they have a carboxyl group. In the condensation reaction, what happens is you have an OH group from one subunit, and we have a hydrogen from another subunit or monomer. Then a condensation reaction occurs, and this connects them together and releases the little baby water over here. So you can think of a condensation reaction, you think of condensation on your cup, water, condensation reactions release water.

Now, we don't always need these big complex polymers; sometimes we need to break them down. So how do we break them down? We do that through hydrolysis reactions. They degrade or break apart long polymer chains through the addition of a water molecule. So this is different; condensation releases water, has water on a cup, you have more of it, whereas the hydrolysis reaction actually uses up water in order to break them apart.

We can think about linear polymerization. It's adding these individual subunits, that's a property, but it's really important to realize that for some macromolecules, including nucleic acids and proteins, the order in which the sequences are added matters a great deal because that determines the sequence of our genes, the sequence of proteins depends on a specific order of these monomers. This can actually really impact biological function depending on when this process occurs, how it occurs, and which unit that's connecting together. So now let's move on.

Stereoisomers

Okay. So, a second property of macromolecules is stereoisomers. And so, what are stereoisomers? Well, they are just mirror images of macromolecules due to an asymmetric carbon atom. You may remember this from chemistry as a chiral center. And so, stereoisomers are 2 molecules that have the same chemical formula, but different physical structures. So they come in two main forms, D and L. And so, let's look at one down here. So, you can see there is, so this is an amino acid. How do we know it's an amino acid? Because it has an amino group, an R group, and a carboxyl group. And these are the two forms. You can see that they're mirror images. If there is a mirror here, then that's what's going to create them. They're mirror images. And so, the asymmetric carbon atom is here because, and it's asymmetric because each, on each side of it, it has different symmetry. It has different things on each side, and so these stereoisomers form with many of the macromolecules. And so there are two forms, the D and the L. So here you have, the D one here and the L one here. And the amino acids, monosaccharides, nucleic acids, and certain lipids, steroid lipids, come in stereoisomer forms. And so, these are important because certain biological functions can only use one form. So, for instance, proteins are only made up of L amino acids, but D amino acids still exist in cells, but they do not have the same function as L. So stereoisomers are a really important property of macromolecules that come into play when looking at specific biological functions. So now let's move on.

Noncovalent Bonds and Macromolecules

Okay. So now, let's talk about the role of non-covalent bonds. Non-covalent bonds are extremely important for macromolecule formation and function. If you remember back, non-covalent bonds are really weak, but they can be strong because they are additive. So, the more non-covalent bonds there are, the forces become stronger as they act together as one non-covalent force. This can affect conformation; macromolecule conformation or structure formation depends on the placement and formation of non-covalent bonds.

This can allow for a really close strong fit between two interacting molecules, for instance, in multiprotein complexes. Different types of functional groups, which, if you remember back to amino acids, would be an R group, allow for different properties and different chemical structures, which then can bond non-covalently in different ways. For instance, we're looking at two amino acids here, lysine and glutamic acid, and you can see that there are actually two types of non-covalent bonds that can form to connect these together. You have the hydrogen bonding, and you have the electrostatic interactions.

Individually, these are really weak bonds, but together they can actually become really strong forces that allow two amino acids to interact or allow two macromolecules to interact and provide different configurations or different functions of the macromolecule itself. So, non-covalent bonds are really important because they're additive. So now, let's move on.

Which of the following is not a property of macromolecules?

• A. They are formed through linear polymerization of individual subunits
• B. They have the ability to form stereoisomers
• C. Noncovalent bonds allow for the formation of complex functions
• D. Covalent interactions allow for stable conformations of macromolecules

Which of the following reactions connects individual monomers together?

• A. Hydrolysis Reactions
• B. Condensation Reactions
• C. Glycolyic Reactions
• D. Monomeric Reactoins

Proteins are most often found in the D form.

• A. True
• B. False

Here’s what students ask on this topic:

What is polymerization in macromolecules?

Polymerization in macromolecules refers to the process where individual subunits, known as monomers, join together to form larger structures called polymers. This process primarily occurs through condensation reactions, where an H⁺ from one monomer and an OH^- from another react to release water (H₂O) and form a covalent bond. This sequential addition of monomers results in the formation of complex structures like polysaccharides, nucleic acids, and proteins. However, it's important to note that lipids do not form through polymerization but through different mechanisms.

What are stereoisomers and why are they important in macromolecules?

Stereoisomers are molecules that have the same chemical formula but differ in their physical structure due to the presence of an asymmetric carbon atom, also known as a chiral center. These molecules come in two main forms: D and L. For example, amino acids can exist as D-amino acids or L-amino acids, which are mirror images of each other. Stereoisomers are crucial in biological functions because only specific forms are utilized by organisms. For instance, proteins are exclusively made up of L-amino acids, while D-amino acids, although present, do not serve the same function.

How do non-covalent bonds influence macromolecule structure and function?

Non-covalent bonds, though individually weak, become strong when they act collectively. These bonds include hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. They play a significant role in determining the conformation and stability of macromolecules. For example, in multi-protein complexes, non-covalent bonds allow for a close and strong fit between interacting molecules. The additive nature of these bonds ensures that the overall structure and function of macromolecules are maintained, which is essential for their biological roles.

What is the difference between condensation and hydrolysis reactions in macromolecules?

Condensation and hydrolysis reactions are two opposing processes involved in the formation and breakdown of macromolecules. Condensation reactions involve the joining of monomers to form polymers, releasing water (H₂O) in the process. This is how complex structures like proteins and nucleic acids are formed. On the other hand, hydrolysis reactions break down polymers into monomers by adding water. This process is essential for degrading macromolecules into their constituent subunits, which can then be utilized or recycled by the cell.

Why is the sequence of monomers important in macromolecules like proteins and nucleic acids?

The sequence of monomers in macromolecules like proteins and nucleic acids is crucial because it determines their specific structure and function. In proteins, the order of amino acids dictates the folding and 3D conformation, which in turn affects the protein's activity and interactions. Similarly, in nucleic acids, the sequence of nucleotides encodes genetic information, guiding the synthesis of proteins and regulating cellular processes. Any alteration in the sequence can lead to changes in function, potentially causing diseases or malfunctions.