Transcription
The subtitles are on! Click CC in the bottom right to turn them off. Follow us on Twitter (@AmoebaSisters) and Facebook! Is it weird to have a favorite protein? Well… I don’t think so. Maybe because my favorite protein happens to remind me of one of my favorite childhood toys, Pac-Man. If you haven’t played Pac-Man before, then chances are… we are much, much older than you. But now you can play it on Google – just Google Pac-Man — it’s a Google Doodle! Anyway, I digress. Look at Pac-Man, you have this little character. It goes around, finds these little dots, and the dots fit right into it. Well a lot of illustrations that you’ll find of enzymes happen to look, to us, a lot like Pac-Man. Remember P for Pac-Man and P for protein. Most enzymes are proteins. In the game we mentioned these little dots that Pac-Man goes after. Good enzymes have a specific area in shape, called an active site, where things can bind, called substrates. It’s very specific binding because the active site is specifically shaped for the substrate that binds there. Very specific. So, what happens when substrates bind an enzyme? Usually, the substrate is held there with weak bonds because it’s not going to stay there forever. Something called induced fit will happen which means the active site can change its shape even more to bind that substrate perfectly. Like… an enzyme-substrate hug. The enzyme can build up or break down substrates that specifically bind to it, and we call the resulting thing a product. An enzyme has the ability to really speed up reactions up to reactions that could technically happen on their own… but with the help of enzymes, they can be helped to make processes effective for life. Let me give you a great real-life example. The enzyme lactase. Another really cool thing about enzymes is that they often end in -ase, like lactase. A lot of sugars, on the other hand, end in -ose, and lactose is an example of a sugar. Lactose is a disaccharide meaning it contains two sugar molecules bonded together. We actually don’t digest it that well in its form. It’s big. The enzyme lactase has the ability to break lactose down into smaller pieces that our body can digest, and this is a much better opportunity than waiting for a chemical reaction with lactose to happen spontaneously. With the lactase enzyme, lactose can be broken down quickly and digested. Now there are some people who don’t produce enough lactase enzyme. They can be what we call lactose intolerant which means consuming foods that have lactose, milk sugar, in them can make them sick. They can’t break down lactose efficiently without the lactase enzyme. Now in that example, one thing needs to be pointed out --- lactase, the enzyme, can break down a lot of lactose, the substrate. Lactase is not used up in the reaction. It’s still there. We call enzymes a catalyst because they can be used over and over again in a reaction. By the way, your digestive system uses all sorts of enzymes. You have lipase that breaks down lipids – which are fats. You have amylase which breaks down starches. You have protease which breaks down proteins. So as you can see, the digestive system is very involved with enzymes. One other thing to point out is that enzymes don’t always work alone. Sometimes they get a little help. Some often overlooked, but essential little helpers are called cofactors and coenzymes. They can bind to the substrate or to the active site. They help the enzyme do its job of building up or breaking down substrates into products. Now you haven’t forgotten our Pac-Man analogy have you? In the game Pac-Man, there are these ghosts. And when they touch Pac-Man, it makes this sound… it’s like… ner ner ner ner ner. Pac-Man’s shape gets all distorted. So, what does this have to do with enzymes? Well, there are no ghosts around. But enzymes have certain ideal conditions that they like. For example, an enzyme that’s in your stomach would have an ideal pH that’s very acidic because the environment in your stomach is very acidic. Different enzymes have different ideal pHs and temperature ranges. If an environment changes from an enzyme’s ideal pH or temperature range, then something that reminds me a lot of that terrible sound I tried to make can happen. The enzyme becomes… denatured! This means its shape gets distorted – it can no longer bind to its substrate. It can no longer function properly. It’s done. Well… that’s a dramatic end for enzymes. Keep in mind that if you have an interest in this topic, a lot of medical researchers have a huge concentration on enzymes. Enzymes regulate a lot of body processes, and a lot of diseases can involve specific enzyme production… or lack thereof. Well that’s it for Amoeba Sisters and we remind you to stay curious!