Good question about spider silk. Scientists are very interested in spider silk because it is stronger than steel. It's true! If you made a steel string as thick as a spiders string, the spider string is stronger. That is amazing, isn't it!


Scientists have studied spider stilk and they know that it is extremely strong. They also know that spider silk is made out of protein. Do you know what protein is? I'll give you a hint, and then maybe you can look it up on the dictionary or an encyclopedia. Protein is the stuff you get from eating meat or beans. It's found in all living things. It is what your muscles are mostly made of. Think about that for a second. That means that spiders have used proteins to make a string that is stronger than steel. Isn't that incredible!


Spiders need to have a strong string because they use the string (called spider silk) for many different things. They use it for constructing their webs, making egg sacs, wrapping in their prey, as a life line when jumping, or dropping to escape, and as a shelter in which it can retreat.


Did you know that spiders can easily recycle their silk? They can eat their old web and use the protein to make a new one. Wow!

Spider threads contain many long molecules called proteins.These proteins are aligned along the thread and all work together to hold up the spider. In part, spider thread is strong because there are so many proteins all lined up together.
However, that's not the whole story. Each protein in the spider's thread is a spring which can be stretched a long way before it breaks. The result is, that it takes a lot of force to stretch a spider's thread, and you have to apply that force over a long distance before it will break. When you apply a force over a distance, physicists says you have done "work". It takes a lot of work to break a spider's thread.

Spider silk is made of several kinds of proteins. These proteins are processed and stored within the spider's abdomen. Spiders typically have six or eight spinnerets, organs at the rear of their abdomen, through which they extrude the silk proteins. During the process of extrusion, the proteins are lined up in a way that locks them into place and makes them very hard to separate. The process of extrusion is under intensive research because very little is known about it. In fact, spider silk is so strong that it is believed to be the strongest known substance for its weight. Believe it or not, the U.S. military has invested a great deal of money into researching the physical properties of silk and how it is made!

Spiders make many kinds of silk. The best known is dragline silk which the spider uses in web construction and also for "hanging around". Dragline silk consists of proteins called spidroins. These are made in the spider's silk glands as a thick paste that is drawn into fibers during spinning. Once spun, the silk is strong and very tough. It not only supports the spider but can trap a very large beetle. Scientists estimate that if dragline silk could be faithfully reproduced with the thickness of a pencil, it would be strong enough to stop a large jet plane in flight.
There are many theories about what makes dragline silk so strong, but no certain answers at this time. Most scientists agree that the strength is related to the spinning process which appears to crystallize parts of the spidroins.

Spider silk is a protein consisting largely of the amino acids alanine and glycine. One attribute that contributes to its strength is that these particular protein molecules tend to associate laterally (side-by-side) in an arrangement called a beta-sheet. These lateral interactions between molecules give extra strength.

Silk is made of protein. There are many kinds of proteins that animals make to form all sorts of materials from muscles, to hooves, to hair. The silk protein comes out of the spider as a liquid, then becomes a solid string that can be used for lots of different jobs. Spider silk is very strong, but so is your hair. Try taking a long strand of hair from a brush or comb. How much weight will it take to break it? Ask an adult to help you attach one end of the hair to a binder clip or ring. They might try tying it or using superglue. Now predict how much weight the hair will hold. Will it hold a pen, a ruler, Your teacher's keys? Now weigh the heaviest object it held (don't forget the clip or ring). Can a thread hold that much wieght?
To learn a lot about spiders and their silk, go to this page and click on "the spinnerettes and properties of silk": spiders There are some great pictures, but your teacher may have to help you with the meanings of some of the words.