Think about It Explain why fatty acids with hydrocarbon chains that contain only single bonds are called saturated fatty acids. Think about It How is the amphipathic nature of phospholipids significant? This video provides additional information about phospholipids and liposomes:.
Think about It How are isoprenoids used in technology? Key Concepts and Summary Lipids are composed mainly of carbon and hydrogen, but they can also contain oxygen, nitrogen, sulfur, and phosphorous. They provide nutrients for organisms, store carbon and energy, play structural roles in membranes, and function as hormones, pharmaceuticals, fragrances, and pigments. Fatty acids are long-chain hydrocarbons with a carboxylic acid functional group. Their relatively long nonpolar hydrocarbon chains make them hydrophobic.
Fatty acids with no double bonds are saturated ; those with double bonds are unsaturated. Fatty acids chemically bond to glycerol to form structurally essential lipids such as triglycerides and phospholipids.
Triglycerides comprise three fatty acids bonded to glycerol, yielding a hydrophobic molecule. Phospholipids contain both hydrophobic hydrocarbon chains and polar head groups, making them amphipathic and capable of forming uniquely functional large scale structures. Biological membranes are large-scale structures based on phospholipid bilayers that provide hydrophilic exterior and interior surfaces suitable for aqueous environments, separated by an intervening hydrophobic layer.
These bilayers are the structural basis for cell membranes in most organisms, as well as subcellular components such as vesicles. Isoprenoids are lipids derived from isoprene molecules that have many physiological roles and a variety of commercial applications. A wax is a long-chain isoprenoid that is typically water resistant; an example of a wax-containing substance is sebum, produced by sebaceous glands in the skin. Steroids are lipids with complex, ringed structures that function as structural components of cell membranes and as hormones.
Bacteria produce hopanoids, structurally similar to cholesterol, to strengthen bacterial membranes. Fungi and protozoa produce a strengthening agent called ergosterol.
Multiple Choice Which of the following describes lipids? All of the options describe lipids. Show Answer Answer b. Molecules bearing both polar and nonpolar groups are amphipathic. Show Answer False. Considered a simple lipid, triglycerides, per WOU, are formed by just two constituent parts: glycerol and three fatty acids. Just like the tail end of a phospholipid, a triglyceride's fatty acid component lacks an electric charge and isn't attracted to water.
Yet unlike a phospholipid, triglycerides serve as an ever-ready source of energy between meals, per the Mayo Clinic. Where do they come from? Breakfast, lunch and dinner. Plus, anytime we take in more calories than we need, the body immediately turns the excess into triglycerides, according to the Mayo Clinic.
They're then stored in fat cells for future use. They're the stuff body fat is made of, according to WOU.
Sometimes accompanied by obesity, type 2 diabetes and arterial hardening arteriosclerosis , high levels up the risk for strokes and heart attacks. The unique structure of phospholipids makes them both fat- and water-soluble, or amphiphilic. The fatty-acids are hydrophobic dislike water , and the phosphate group and glycerol are hydrophilic attracted to water.
The amphiphilic nature of phospholipids makes them very useful for several functions in the body. Every cell in the body is encased in a membrane composed primarily of a double layer of phospholipids also known as the phospholipid bilayer , which protects the inside of the cell from the outside environment while at the same time allowing for transport of fat and water through the membrane. The phospholipid bilayer consists of two adjacent sheets of phospholipids, arranged tail to tail.
The hydrophobic tails associate with one another, forming the interior of the membrane. The polar heads contact the fluid inside and outside of the cell. Another important role of phospholipids is to act as emulsifiers. Emulsions are mixtures of two liquids that do not normally mix oil and water, for example. Without an emulsifier, the oil and water separate out into two layers.
Because of their ability to mix with both water and fat, phospholipids are ideal emulsifiers that can keep oil and water mixed, dispersing tiny oil droplets throughout the water. Lecithin—a phospholipid found in egg yolk, soybean, and wheat germ—is often used as a food emulsifier. Emulsifiers also play an important role in making food appetizing; their inclusion in foods like sauces and creams makes for a smoother texture and prevents the oil and water ingredients from separating out.
They also can extend shelf life. Because body fat cushions some internal organs, it can help absorb shock and protect organs, in the event that an animal or human is badly injured. Triglycerides also help to give food its flavor. Phospholipids are similar to triglycerides, but they do vary slightly in form and function. While triglycerides have glycerol and three fatty acids, phospholipids have glycerol, two fatty acids and a phosphate.
Phosphates are molecules with charges and have oxygen and phosphorus. Because fats must contain three fatty acids by definition, phospholipids are not fats, as triglycerides are, despite their similarities.
Like triglycerides, phospholipids are crucial to the formation of lipid bilayers, which help maintain the structure of cell membranes. However, phospholipids have a more rigid chemical structure than triglycerides do, so they make cell membranes tougher and help them to hold their shape better than triglycerides alone could. Fat cells do not store phospholipids.
Instead, phospholipids help break down fats during the digestive process. In the small intestine, bile is an alkaline fluid that helps to break down food. Phospholipids exist in bile and specifically help to break down fats.
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