Chitin - Online Tutor, Practice Problems & Exam Prep

Chitin is a homopolysaccharide composed of repeating units of N-acetylglucosamine (NAG), linked by β-1,4 glycosidic bonds, which provide structural support. Found in the exoskeletons of insects and crustaceans, chitin is a non-branched polysaccharide. Its structural function is emphasized by the beta configuration of its linkages. Understanding chitin's role in these organisms highlights its importance in biological structures and the diversity of polysaccharides in nature.

Chitin

In this video, we're going to begin our lesson on chitin. So the polysaccharide chitin is a homopolysaccharide, which of course we know from our previous lesson videos just means that chitin is made up of only one single type of repeating sugar unit. And that repeating sugar unit is going to be a NAG molecule. Now NAG is just an abbreviation, and so it's an abbreviation for N-acetylglucosamine. And so you can see the NAG in here. And, of course, this is the NAG sugar molecule. Now if you take a look at our image right here, notice that all the NAG molecule really is is just taking a beta-D-glucose molecule that we're already familiar with and replacing the hydroxyl on the C2 carbon with this N-acetyl group that we see over here and so, really, NAG is just a sugar derivative. It's an amino sugar since it has this nitrogen atom right here. And so all of these NAG repeating molecules in the chitin structure are going to be covalently linked to each other via beta-1,4-glycosidic linkages. And recall that the beta configuration of these linkages reminds us that its function is going to be structural. And so as we'll see, beta configurations in the glycosidic linkages of polysaccharides tend to be structural in their function.

Now in terms of the organisms that we can find that contain or use the polysaccharide chitin, these tend to be animals. Specific types of animals that have hard exoskeleton shells, such as insects like beetles or crustaceans like lobsters or crabs that again have these hard exoskeleton shells. And so, again, chitin is going to make up the structural parts of these shells. Now in terms of being a branched polysaccharide, we can say that chitin is not going to be branched. So there's absolutely no branching in the chitin structure. And so if we take a look at our image down here in the middle, notice we have these NAG molecules here and here. And these NAG molecules are linked via beta-1,4-glycosidic links. And so, down below, we can write that they're linked through these β-1,4-glycosidic linkages. And again, the beta configuration reminds us that chitin is going to have a structural function.

So this here concludes our introduction to chitin. And as we move forward in our course, we'll be able to get a little bit of practice applying these concepts. So I'll see you guys in our next video.

Indicate whether or not each of the following characterizations applies to the following:

(1) Chitin only, (2) Cellulose only, (3) Both Cellulose and Chitin, (4) Neither.

a) Structural polysaccharide: ____________.

b) Monomers are glucose amino sugar derivatives: ____________.

c) Glycosidic linkages are all (β-1,4): ____________.

d) Homopolysaccharide: ____________.

Alright. So this practice problem wants us to indicate whether each of the following characterizations applies to chitin only, cellulose only, both cellulose and chitin, or neither cellulose nor chitin. Notice that the first characterization here is "structural polysaccharide." Of course, we know from our previous lesson videos that both cellulose and chitin are structural polysaccharides. For that reason, we can go ahead and put the number 3 in this line to indicate both cellulose and chitin are structural polysaccharides. Recall that cellulose is a structural polysaccharide that makes up a major component of plant cell walls. Chitin, on the other hand, is a structural polysaccharide that makes up the hard exoskeleton shells of some specific animals. Moving on, the next characterization we have here is "monomers are glucose amino sugar derivatives." These glucose amino sugar derivatives that they are referring to from our previous lesson videos are the NAG molecules, or the N-acetylglucosamine molecules. These glucose amino sugar derivatives, or these NAG sugar molecules, are only found in chitin. Therefore, for this item, we can go ahead and put number 1 for chitin only. Next, it states "glycosidic linkages are all beta-1,4." Recall from our previous lesson videos that both cellulose and chitin have beta-1,4 glycosidic linkages that link their monomers together, so we can once again indicate 3 here, since this applies to both cellulose and chitin. Lastly, the term "homopolysaccharide" also applies to both cellulose and chitin. The prefix 'homo' means the same, indicating that they are made up of the same exact type of monosaccharide repeatedly linked together over and over again. This concludes the answers to our practice problem, and I'll see you guys in our next video.

Which of the following statements best describes the main structural difference between cellulose and chitin?

• A. Chitin contains α-1,4-glycosidic linkages while cellulose contains β-1,4-glycosidic linkages.
• B. The C-2 carbon in the cellulose monomer contains an N-acetylamino group instead of an -OH group.
• C. Cellulose is a linear, unbranched homopolysaccharide while chitin is a branched homopolysaccharide.
• D. The C-2 carbon in the chitin monomer contains an N-acetylamino group instead of an -OH group.

Here’s what students ask on this topic:

What is chitin and where is it found?

Chitin is a homopolysaccharide composed of repeating units of N-acetylglucosamine (NAG), linked by β-1,4 glycosidic bonds. This structure provides significant structural support. Chitin is primarily found in the exoskeletons of insects and crustaceans, such as beetles, lobsters, and crabs. These organisms utilize chitin to form hard, protective shells. The beta configuration of the glycosidic linkages in chitin emphasizes its role in providing structural integrity. Understanding chitin's presence in these organisms highlights its importance in biological structures and the diversity of polysaccharides in nature.

What is the chemical structure of chitin?

Chitin is composed of repeating units of N-acetylglucosamine (NAG), which is a derivative of glucose. In NAG, the hydroxyl group at the C2 carbon of glucose is replaced by an N-acetyl group. These NAG units are linked together by β-1,4 glycosidic bonds. The chemical structure can be represented as:

$C_8{H}_{13}{O}_5{N}_1$

The β-1,4 glycosidic linkages contribute to the rigidity and structural function of chitin.

What is the function of chitin in organisms?

Chitin serves a structural function in organisms. It is a key component of the exoskeletons of insects and crustaceans, providing rigidity and protection. The β-1,4 glycosidic linkages in chitin's structure contribute to its strength and durability. This makes chitin an essential material for the formation of hard, protective shells in organisms like beetles, lobsters, and crabs. By providing structural support, chitin helps these organisms maintain their shape and defend against physical damage and environmental threats.

How does chitin differ from cellulose?

Chitin and cellulose are both structural polysaccharides, but they differ in their monomer units and specific functions. Chitin is composed of repeating units of N-acetylglucosamine (NAG), while cellulose is made up of repeating units of β-D-glucose. Both polysaccharides have β-1,4 glycosidic linkages, which contribute to their structural roles. However, chitin is found in the exoskeletons of insects and crustaceans, whereas cellulose is a primary component of plant cell walls. The presence of the N-acetyl group in chitin's monomer units distinguishes it from cellulose and contributes to its unique properties and functions.

Is chitin a branched or unbranched polysaccharide?

Chitin is an unbranched polysaccharide. It consists of repeating units of N-acetylglucosamine (NAG) linked by β-1,4 glycosidic bonds in a linear fashion. There is no branching in the structure of chitin, which contributes to its rigidity and structural function. The linear arrangement of NAG units allows chitin to form strong, fibrous structures that are essential for the exoskeletons of insects and crustaceans.