The Chemistry of Spiders

Ouch! Spider bites hurt! But why do they hurt? What kind of a chemical reaction is occurring within the body? Woah woah. Chemical reaction? I don’t want to hear about boring chemistry.

Actually, I do think you want to hear about chemistry! Spiders introduce fascinating concepts that are interesting to not only chemistry nerds. Think about the spider webs in that corner of your room right now. They stick to the walls every which way, but it’s not really common knowledge why this happens. Today, we will introduce much of the information that is available about spiders and their annoying webs, as well as the venom that the poisonous ones carry.


First off, let’s consider spider silk and its strength, meaning why it can actually hold together. There are many different specific types of this silk, like dragline or viscid, but for sake of simplicity, we will consider them as a whole. As can be seen from this link, much of the composition of spider webs is from protein structures and amino acids, and things labeled as “polar,” which is basically an unequal sharing of electrons in a bond. Something that immediately comes to mind are intermolecular forces. Wait, WHAT? You don’t know what those are? Well, intermolecular forces, or IMF, are the forces between molecules in larger compounds that hold them together, such as London Dispersion force, and dipole-dipole interaction. London Dispersion force is the force that is exerted when a molecule becomes slightly negative from a collection of its electrons floating towards one side. This creates a polar molecule, which gets attracted to other polar molecules beside it to create these IMF’s. The dipole-dipole interaction is quite similar, except the polarity of the compound is caused by the difference in electronegativity of the elements in the molecules, here’s a diagram to hopefully clear that up:



According to the source that you were directed to earlier, a large part of why spider silk is so strong is due to these IMF’s. Many of the bonds end up being polar and strong intermolecular forces can be attributed to being large causes of the strength of spider silk. To be more specific, arginine, an amino acid, exhibits polar effects, and is located in spider webs. Notice the diagram at the right to see the polar molecule, arginine. There are, of course, a few other hypotheses and reasons as to why spider silk is so strong, like the protein-protein interaction due to hydrophobic effects, but for sake of simplicity we will go into more detail on those in following blog posts.

Phew, well silk is out of the way now! Don’t get too sad though, because now we get to talk about spider venom! Okay, so let’s just get the basics out of the way. There are two types of spider venom: neurotoxic and cytotoxicNeurotoxic is the type of venom that attack the nervous system, while cytotoxic venoms attack the tissues. Now, let’s get to the nitty-gritty of this. Since spiders are not the only creatures that produce venom, it may be a good idea to look at a broader image of venom at first, in order to get a sense of how this stuff works. A common way that venoms work is through enzymes and hydrolysis. Hm, yeah, I know.

spider_hydrolysisI should probably explain what those terms are! Enzymes are usually proteins that catalyze reactions, or speed up certain reactions. Hydrolysis, on the other hand, is the separation of chemical bonds using water. Combining these two things make hydrolytic enzymes, which break down bonds using water to corrode the tissue of the victim, making it more liquefied. More specific to our topic, a study was conducted to obtain information on the toxins from spiders, so click that link if you want more information, but we’ll discuss most of this here. Venoms use those hydrolytic enzymes that we mentioned before, but they’re made up of simple amino acids and amino acid derivatives, not too dissimilar from things that make up spider silk! Though this isn’t quite  a detailed explanation of what chemical reaction occurs in the body with spider venom, it is actually difficult to describe this process, and scientists are only discovering things about it now. Further blog posts will investigate these new discoveries, that can be seen in this link.

To sum up all of this information you have just seen, let’s go over some of  the main points. First, we learned about polarity, and intermolecular forces. Do you remember what either of those are? Of course you do, because you’ve been reading our blog very carefully! We’ll tell you anyway though. Polarity is the unequal distribution of electrons in a molecule or bond, due to electronegativity, or the tendency to gain electrons. Intermolecular forces occur from things related to polarity, and are the forces that hold together many molecules, like dipole-dipole forces and London dispersion forces. The next thing mentioned was hydrolysis and enzymes. Both are commonly used as biology terms, but they are actually really pertinent towards chemistry! Hydrolysis is the breakdown of molecules using water, and enzymes speed up reactions, or lower the activation energy. We don’t want to overwhelm you just yet, but we may mention this idea of activation energy in our next blog post. Click this link if you’re just DYING to learn what this is.

spider Anyway, I hope you walk away from this blog knowing more than you did on spiders and their chemistry. This was more of an introduction towards the idea of spider chemistry, and there will definitely be more hard-hitting evidence in the next blog post. Thank you for reading.

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