 What do all of these things have in common? They are all made of protein. In this video, we're going to discuss the structure and uses of protein molecules. Proteins are long chain molecules made of strings of amino acids joined together. All amino acids are compounds with a similar basic structure. They have an amino group, a carboxyl group and a side chain or R group that is specific to each amino acid. There are 20 different amino acids. All of the different proteins are made from these 20 amino acids. The variation in proteins is caused by the order of amino acids, the chain length, and by folding the chain in distinct ways. As part of a balanced diet, roughly how much of it do you think should be protein? About 14%. Sources of protein in our diets include meat, fish, eggs, cheese, beans and nuts. But did you know that proteins are large molecules, too large for our bodies to absorb? That's why enzymes in our digestive system break down proteins into amino acids, which are small enough to pass from our digestive system into our blood to be assimilated by the body. When we absorb these amino acids, they are then built back up into proteins and used in a variety of ways. To test food for protein, you need to use copper sulfate solution and sodium hydroxide solution. These two liquids together may be called biret solution, which is a pale blue liquid. To begin the first experiment, first make a solution of the food sample by dissolving it in some water. You may need to grind this up first with a pestle and mortar. Next, add a few drops of sodium hydroxide solution to your food solution, then a few drops of copper sulfate solution. If the solution turns lilac or purple, the food contains protein. If the food solution remains blue, no protein is present. But how does our body build proteins from amino acids? Our DNA acts as a set of instructions for how to build proteins. Each individual's DNA is made of slightly different genes, which explains some of the differences between people. For example, hair color and eye color, a change in the DNA called a mutation, can lead to a protein with a different structure being produced. This can lead to albinism for example. To learn more about mutations, you can watch this video. So what are proteins used for in the body? The answer is they are used in thousands of ways. Our hair, nails, skin and muscles are all examples of structures made of protein. Many hormones including insulin are made of protein. Antibodies made by white blood cells to protect us from diseases are also made of protein. Enzymes, biological catalysts found inside our body, are made of proteins too. You can learn more about enzymes in this video. And last but not least, proteins are also used to move some substances across cell membranes in active transport. For example, to absorb glucose in the small intestine. So now you can see just how important proteins are. If you liked the video, give it a thumbs up. Please, I can share our videos with your friends. If you have any questions, comment below. If you have any questions, why not check out our Fuse School app as well. Until next time.