Chapter FiveThe lipids fats, oils, phospholipids, and sterols课件.ppt

Chapter FiveThe lipids: fats, oils, phospholipids, and sterols 1 Introduction 1.1 Usefulness of fats in the body padding: protecting internal organs from shock insulation: against temperature extremes major material of cell membranes raw materials: converting to hormones, bile, Vitamin A, E, D, K. 1.2 Usefulness of fats in food nutrient: providing essential fatty acids energy: providing a concentrated energy source transport: carrying fat-soluble vitamins sensory: taste and smell of foods texture: helping make foods tender satiety: feelings of fullness appetite: stimulating the appetite raw materials: for making needed products 2 Major lipids 2.1 Triglycerides made of three fatty acids and a molecule of glycerol 2.2 saturated and unsaturated fatty acid Saturation: number of hydrogen in fatty acid chain Saturated fatty acid: every available bond is holding a hydrogen. Unsaturated fatty acid: possesses one or more points of unsaturation. soft or hard fat: The more unsaturated, the more liquid; the more saturated, the firmer the fat is. lard----most saturated----hardest chicken fat--less saturated--somewhat soft safflower oil----most unsaturated---liquid 2.3 Other lipids Phospholipids Made of a molecule of glycerol, two fatty acids, a phosphorus molecule are emulsifiers, helping fats travel across the lipid-containing membranes of cells into the watery fluids. Sterols cholesterol, vitamin D, sex hormones Cholesterol make bile a part of every cell cause heart attacks and strokes. 3 Lipids in the body 3.1 Digestion of fats the action of bile in fat digestion 3.2 Lipoproteins VLDL: carry triglycerides and other lipids made in the liver to the body cells LDL: made from VLDL HDL: carry cholesterol from body cells to the liver distinction between LDL and HDL LDL: larger, lighter, and more lipid filled HDL: smaller, denser, and packaged with more protein LDL: from liver to tissues HDL: from tissues to liver LDL: a sign of high risk of heart attack HDL: