Chapter Four.ppt

Chapter Four The Lipids: Fats Oils What are Lipids? A family of compounds that includes Triglycerides (fats oils) Fats: lipids that are solid at room temperature Oils: lipids that are liquid at room temperature Phospholipids Sterols (cholesterol). I. A Primer on Fats The Functions of Fat in the Body Energy source esp. for muscles Serves as an energy reserve 1# body fat contains 3500 kcal 30-50# of stored fat Cont’d Major component of cell membranes Nourishes skin hair Insulates the body from temperature extremes Cushion the vital organs to protect them from shock B. The Functions of Fat in Food Provide calories (9 per gram) Provide satiety Carry fat-soluble vitamins essential fatty acids Contribute aroma flavor Lipid Terminology Triglycerides: the major class of dietary lipids, including fats oils Made up of 3 units known as fatty acids and 1 unit called glycerol (backbone) Comprise about 95% of lipids in food and the human body Cont’d Phospholipids: 2nd of three main classes of lipids similar to a triglyceride, but contains phosphorous Sterols 3rd of three main classes of lipids; Cholesterol one of the sterols manufactured in the body for a variety of purposes Cont’d Fatty acids: basic units of fat composed of chains of carbon atoms an acid group at one end and hydrogen atoms attached all along their length II. A Closer View of Fats Chain Length (number of carbons linked together) Shorter = more soluble in water Saturated vs. Unsaturated (number of hydrogens the chain is holding) Maximum = saturated Unsaturated = one or more is missing Point of unsaturation = site where hydrogen is missing Cont’d Saturated fatty acid: a fatty acid carrying the maximum possible number of hydrogen atoms Animal foods such as meat, poultry and full-fat dairy products Tropical oils such as palm and coconut Cont’d Unsaturated fatty acid: a fatty acid with one or more points of unsaturation. Found in foods from both plants animal sources Monounsaturated fatty aci