Growing up in central Wisconsin, I spent a lot of time outside. In the spring, I'd smell the heady fragrance of lilacs.
In the summer, I loved the electric glow of fireflies as they would zip around on muggy nights. In the fall, the bogs were brimming with the bright red of cranberries.
Even winter had its charms, with the Christmassy bouquet emanating from pine trees. For me, nature has always been a source of wonder and inspiration.
As I went on to graduate school in chemistry, and in later years, I came to better understand the natural world in molecular detail. All the things that I just mentioned, from the scents of lilacs and pines to the bright red of cranberries and the glow of fireflies, have at least one thing in common: they're manufactured by enzymes.
As I said, I grew up in Wisconsin, so of course, I like cheese and the Green Bay Packers. But let's talk about cheese for a minute.
For at least the last 7,000 years, humans have extracted a mixture of enzymes from the stomachs of cows and sheep and goats and added it to milk. This causes the milk to curdle—it's part of the cheese-making process. The key enzyme in this mixture is called chymosin.
I want to show you how that works. Right here, I've got two tubes, and I'm going to add chymosin to one of these.
Just a second here. Now my son Anthony, who is eight years old, was very interested in helping me figure out a demo for the TED Talk, and so we were in the kitchen, we were slicing up pineapples, extracting enzymes from red potatoes and doing all kinds of demos in the kitchen.
And in the end, though, we thought the chymosin demo was pretty cool. And so what's happening here is the chymosin is swimming around in the milk, and it's binding to a protein there called casein.
What it does then is it clips the casein—it's like a molecular scissors. It's that clipping action that causes the milk to curdle.
