Hey this is Mr. W. Welcome to Episode Three of "Thinking Biologically: The Four Biomolecule Families. The molecules that make up living things — biomolecules — fall into four families, and three of them are right here in this peanut butter and jelly sandwich. The bread and jelly are carbohydrates, family number one. The peanut butter has fat which is a representative of family number two: the lipids. It also has lots of protein, which is our third family. The fourth family is here too, but it's not a food group. It's the nucleic acids: the molecules of heredity. The goal of this video is for you to be able to describe each biomolecule family. Right now we're just going for the big picture: the overall structure and the biological importance: This video has a follow-up quiz that I strongly suggest you try. You'll see that you'll remember so much more if your learning is active. I also want you to know that I use a bunch of structural formulas in this video and if you need to, you can learn about how they work in my tutorial and video that's called "Covalent Bonds." It has a section about structural formulas. Let's go! Carbohydrates are the first family that we're going to consider. Like all the biomolecules they're made from building blocks that are chemically combined to create larger molecules. Those building blocks are called monomers, and I have an entire video explaining how these are chemically combined in cells to create larger molecules. Here's one carbohydrate monomer. It's called glucose, C6H12O6. It's made by plants, algae, and photosynthetic bacteria during photosynthesis. Glucose is a simple sugar or a monosaccharide, and monosaccharides are the monomers of carbohydrates. Put two monosaccharides together and you have a disaccharide like sucrose, also known as table sugar. You like sugar? Me too. That's because we're primates, a group of animals that evolved in trees eating fruits, Primates like us love sugars because they're a quick source of energy and so do lots of other animals. For long term storage of carbohydrate energy plant cells chain together hundreds or thousands of glucose molecules and create starch. It's in plant parts like seeds and roots and it's found in foods like bread, pasta, potatoes and rice. Starch is a polysaccharide: many monosaccharides linked together. Another polysaccharide isn't for energy storage but for structure. It's cellulose or plant fiber. It makes up plant cell walls and it's found in foods like lettuce, celery, and other vegetables. Cellulose is also in wood, cotton, and paper: the basic biomaterials of civilization. Let's move on to biomolecule family number two: the lipids. Lipids include fats like butter, oils like vegetable or olive oil, and waxes. The key characteristic of the members of this family is that they're entirely or mostly nonpolar. Fats and oils are chemically very similar. You can see in this structural formula of fat that one of their main building blocks is what's called a fatty acid. Fatty acids have a long hydrocarbon chain and those hydrocarbon chains are loaded with chemical energy. That's why fats and oils have more food energy than any other type of food: 9 calories per gram. That's why bears fatten up for the winter. Fats and oils are also used for insulation and that's why whales have a lot of fat. Waxes are used for waterproofing the surface of every leaf is covered with wax. Here's the structural formula of another type of lipid: a phospholipid. These molecules are the key components of cell membranes. Remember how I said that lipids are nonpolar? Phospholipids are different. They have a polar side and a non-polar side. When phospholipids are placed in water they spontaneously form structures called bilayers which are the basis of cell membranes. Another member of the lipid family are steroids. Steroids consist of 4 fused carbon rings with other atoms attached. Steroids comprise some extremely important hormones such as the masculinizing hormone testosterone and the feminizing hormone estrogen. All right! We're halfway there. Feel like this is making sense? Please leave me a comment. How about something like "Got it Mr. W.! Proteins make up structures like skin, hair, fingernails, and the lenses of our eyes. Proteins like muscle tissue contract, enabling movement. Proteins called enzymes catalyze and control chemical reactions in living things. Another group of protein action molecules are the antibodies . antibodies play a key role in our immune system, fighting off infections. In terms of food, meat is mostly muscle protein. That's what you're eating — muscle tissue — when you eat chicken or beef or fish. Egg white is protein. The chemistry of proteins is complex. For now, all you need to know is that the monomer of proteins are amino acids and there are 20 of them. The nucleic acids make up the last biomolecule family. DNA, the molecule of heredity is a nucleic acid. So is RNA. These molecules store and transmit genetic information. The monomers of nucleic acids are nucleotides. One nucleotide, ATP, is life's key molecule for storing and releasing energy and getting work done. You did it! Those are the four biomolecule families. To consolidate all of this material in your memory I want you to do two activities on my website. They're really going to help you learn. They're free you don't need a subscription. One is an interactive concept map where you drag labels into the right spot The other is a quiz that's a kind of word game. Don't worry about getting the answers right on the first try. With me you always get another chance. The goal is learning B-I-O-L-O-G-Y. You can use the tiny URL on the screen or the video card or the link below. When you're done come on back so I can give you some suggestions about how to continue learning biochemistry. Between now and the next video this week there's a lot to do. I'd like you to watch four short videos at sciencemusicvideos.com. and do the associated tutorials. The first one is about the structure of carbon and what characteristics make it life's central element. The second is about functional groups. These are small groups of atoms that give organic molecules their distinct properties. The third tutorial is about monomers and polymers. The fourth is about carbohydrates like this apple I talked about in the first video of the series. Please do a couple of things. Subscribe to my channel. I love comments and questions, so please leave them below. I'll see you at sciencemusicvideos.com (now Learn-Biology.com) and I'll see you next week right here for the next episode of thinking biologically [Music]