Picture this. You’re an imperial guardsman in service to the Imperium of Mankind and the Tyranids have come knocking. They’re coming for you now. As you stand ready in your trench, lasgun in hand you wonder; what are they made of?
There are a few options.
Sugars are a lot stronger than they get credit for. When you think of sugar you might be thinking of the fructose and sucrose in our food. These are all longer chains of glucose, a small sugar molecule that is used by many living things as fuel and as an important building material. Even cellulose is a sugar.
And chitin is, you guessed it, a sugar.
It might seem strange to think that the white powder on your donut can be a part of the same material found in insect exoskeletons. But it’s really not that unusual.
Chitin is a polymer, more specifically a polysaccharide. It’s made of many smaller subunits of modified glucose. Along each unit is weak, but together they form long chains capable of aggregating to form materials that are much stronger than the individual parts.
Chitin currently has multiple uses in agriculture and industry. It can be used to make edible films and strengthen paper. Or it can be used by farmers to trigger immune responses in plants to protect against insects. There are also potential applications for chitin in medicine, biodegradable plastics, and building on Mars.
Now what if you live on a planet without trees and other plants? Maybe the natives consist of giant armored insects and walking mushrooms. What will you wear? You could kill one of the insects and wear it’s shell, but I like to think that you would be more creative. After a few years living on the planet you and your people might find a way to take the chitin plates of the local insects and spin them into durable fibers for making clothes and all sorts of tools.
If you read the first post in this series you’ll remember that proteins are how living things do stuff. Your hair and nails? That’s protein. You might think that because you can cut both with scissors that keratin is weak.
You’d be wrong.
Others in the animal kingdom put their keratin to much better use. Scales are made of keratin and so are claws and horns.
There are two kinds of keratin, alpha and beta. Keratin is a helical protein, it forms long strange and curls around itself. Alpha and beta refer to the direction of the curl. Mammals and certain fish have alpha keratin, reptiles and others have beta.
One thing that makes keratin especially strong is the disulfide bonds between the keratin strands. Bonds like this between polymer strands is called cross-linking. Besides being used in our bodies, cross-linking is often employed by polymer chemists to create strong and resilient materials.
Venom is used by many animals for defence and attack, and you do not want to be on the receiving end. There are three ways that venom can inflict pain; it can kill cells, it can target nerves, or it can target muscles.
Obviously there are many different kinds of venom. Not all will kill humans, at least not without a lot of it. But there are some horrifying ways that they can kill a human if they do. Venom can kill cells, target the nervous systems, or target muscles.
According to “Snake venom components and their applications in biomedicine” by Koh et al., neurotoxins are the most studied class of snake venoms. One of these neurotoxins are the alpha-neurotoxins which specifically target nicotine acetylcoline receptors.
Receptors are specific proteins on the outside of cells designed bind to specific chemicals. You can think of receptors as sensors on the outside of a cell and they are how cells communicate through chemical signals. By blocking these receptors, alpha-neurotoxins prevent the normal function of these nerve cells, and death follows soon after.
You might be surprised to know that while these toxins are deadly they also have uses in healing. Receptors are incredibly important in biology. It’s hard to understate just how important these are. Because these toxins are so specific to certain receptors they are very useful for for figuring out what those receptors do. For example, in biochemical research it is common to block a receptor and see what happens to the cells after they have been deprived of it’s use. This data then yields important clues to the function of that receptor.
But there’s more. When used in the right dose, these neurotoxins can reduce inflammation and pain. So these toxins can not only cause pain, but show us how to negate them. If they are used carefully.
Now let’s return to you, the guardsman. You’re stuck in your trench. First come the small beasts, ferrocious dog-like things. They’re soft and they fall easily to your lasguns but there are too many of them. They dive into your trench and tear your friends apart with their keratin claws. You think one is coming for you, but before it can sink it’s claws into you feel yourself picked up by a pair of chitinous claws.
You look up. Above you is gaping maw flanked by two horrible mandibles. A pointed tongue flicks out and pierces your skin. Your blood congeals and turns to jelly and slowly every fades as you are pulled into it’s jaw…