Transcript 2/4 Lipids
Lipids Pick up the handout in the back of the room. Homework Read p. 62-64, “Lipids” The purpose of our next unit: Understanding how a cell membrane regulates what goes in and out of a cell. Questions to Ponder Why do grocery store owners constantly spray their fruits and vegetables with water? We have “reduced salt areas” on our highways to preserve the plants that grow along the highway. Why would salted roads be bad for them? Why would shipmen and pirates have died if they’d drunk ocean water while sailing at sea? Check out a nutrition panel… – – – – – – Saturated fat? Unsaturated fat? Polyunsaturated fat? Fatty acids? Trans fats? Hydrogenated fat? What do you know about… Why are we told that saturated fats are bad for us and hydrogenated fats are REALLY bad for us, while unsaturated fats aren’t so bad? Macromolecules All matter is made of atoms, so understanding living things means understanding some basic chemistry. A compound is two or more atoms bonded together. A molecule is a compound where the atoms bond to each other by sharing their electrons with one another. A macromolecule is a very large and complex molecule. Biochemistry! An organic compound is a compound where, in at least one place, two carbons are bonded to each other. (think organic = organism) – Organic compounds are the chemical basis of living things. There are four types of organic macromolecules that are especially important and are only found in living things. I guarantee you’ve heard of all four of them before. Macromolecules Lipids Nucleic acids Amino acids Carbohydrates We’ll learn about them one by one over the semester. Starting, today, with the lipids. Lipids There are many types of lipids, including steroids, cholesterols, sphingolipids, prenol lipids, and saccharolipids. We’re going to focus on just two types: – Fatty acids and triglycerides – Phospholipids Lipids Easy to recognize! They’re made of long chains of carbon atoms (C) with hydrogen atoms (H) attached. Here’s one example (three different ways of representing the same chemical): Palmitic acid Lipids Scientists often abbreviate that chemical diagram to something like this: Saturated vs Unsaturated Notice on this lipid how there are all these hydrogen atoms surrounding the carbons. This is a saturated fat. Saturated means “full of something.” Saturated fats are completely full of hydrogens. Saturated vs Unsaturated Unsaturated means “not full.” Unsaturated Fats = carbons aren’t totally surrounded by hydrogens. When that happens, the carbons that aren’t surrounded hold each other more tightly, and you get this: Saturated vs Unsaturated The difference between saturated and unsaturated is being full of hydrogens. When a fat is saturated, it’s in a straight line. When it’s unsaturated, it gets a kink in it. This totally changes how it behaves, and can seriously affect your health. “Good” vs “Bad” fats The straight chains pack together into a nice regular structure, making the saturated fat solid at room temperature. The crooked chains can’t pack closely together, making the unsaturated fat liquid at room temperature. Saturated = straight chains pack together to make it solid. Unsaturated = crooked chains can’t pack together, it stays a liquid. Good vs. Bad fats – Saturated fats and hydrogenated fats (man-made saturated fats), because they’re solid, can clog up an artery like a traffic jam, preventing blood from flowing through. Unsaturated fats, being liquids, don’t do that. – Saturated fats in their rigid regular structures are also harder to break down. So, the body tends to break up and use unsaturated fats for energy, but tends to store saturated fats in specialized fat cells. “Good” vs “Bad” Fats So, as best as scientists can currently figure out, you shouldn’t eat many saturated or hydrogenated fats. Eat unsaturated fats. Eating a completely fat-free diet is extremely unhealthy, because lipids aren’t just around to ambush your arteries. You would die without lipids, they serve essential life functions. Phospholipids Phospholipids – Make up cell membranes. Polarity Water is polar, like a magnet. One end of it has a positive charge, the other end has a negative charge. When it meets other compounds that are also polar, just like magnets, they tend to attract each other and stick together. We call compounds like that hydrophilic. Latin/Greek: Phil = Love <3 Polarity If a molecule isn’t polar, it tends to be hydrophobic. Water and a hydrophobic compound move away from each other. Latin/Greek: Phobia = Fear Polarity The phosphorus end is polar, so it’s hydrophilic. The two lipid chains are hydrophobic, they separate from water just like oil. Micelles If you get more than one phospholipid in the same place, they act in a predictable way because of the attraction and repulsion from the water they’re in. Follow orders, let us see how it works… http://telstar.ote.cmu.edu/biology/Membra nePage/index2.html Et voila… The inevitable chemical result is a membrane! We call these layers of two lipids a phospholipid bilayer. (Latin/Greek table: Bi = two.) The plasma membrane of every living thing is a phospholipid bilayer. Et voila… QuickTime™ and a decompressor are needed to see this picture. Macromolecule Table S hape Carbohydrate Amino acid Nucleic acid Lipid Name Biochemistry Types Key Locations Functions/Uses Other