Lipids: Types, Functions, and Importance

1. Chapter 10 Notes Lipids • Lipids are organic compounds that are insoluble in water and have a greasy feel • There are three types of lipids in foods and the human body • 1. Glycerides • 2. Phospholipids • 3. Sterols

2. Lipids • Lipids have two main parts, a glycerol molecule and a fatty acid • Glycerol has three hydroxyl groups that easily react with other compounds • Fatty acids are organic molecules that have a carbon chain with a carboxyl group at one end • All organic acids have a carboxyl group- COOH

3. Glycerides • Glycerides are molecules that have a glycerol base • Monoglyceride- has one fatty acid attached at a hydroxyl group • Diglyceride- has two fatty acids attached at a hydroxyl group • Triglyceride- has three fatty acids attached at a hydroxyl group, contribute flavor, satiety, and tenderness to food

4. Glycerides • Essential Fatty Acids- These are fatty acids that are not produced by the body • Linoleic acid and linolenic acid are the only two essential fatty acids • They are found in most plant and fish oils

5. Phospholipids • Phospholipid- A glycerol base with two fatty acids and a phosphorus-containing acid attached. • The fatty acids are soluble in fats while the phosphorus-containing acid is soluble in water • They help keep foods like mayonnaise from separating

6. Sterols • Sterols- complicated molecules derived or made from lipids • Examples include cholesterol, vitamin D, steriods

7. Saturated vs. Unsaturated Fats • Saturated- When fatty acids have the maximum number of hydrogen atoms • This means that there are no double bonds in the carbon chain structure • Unsaturated- When a fatty acid does not contain all the hydrogen atoms it could contain • This means that there is at least one double bond in the carbon chain

8. Saturated Fats • Examples- butyric acid in butter, stearic acid in beef fat, coconut oil, palm kernel oil, palm oil

9. Unsaturated Fats • Monounsaturated- Fatty acids that have one double bond in the carbon chain • Examples- olive oil, almonds, walnuts, canola oil, margarine • Polyunsaturated- Fatty acids that have two or more double bonds in the carbon chain • Examples- Safflower oil, sunflower oil, corn oil

10. Melting Point and Solidification Point of Fat • Melting Point- The temperature at which a lipid is completely liquid • Solidification Point- The temperature at which all lipids in a mixture are in a solid state (they have regained their original firmness)

11. Fats vs. Oils • Lipids that are solid at room temperature are called fats • Fats at room temperature are usually saturated • Lipids that are liquid at room temperature are called oils • Oils at room temperature are usually unsaturated

12. Hydrogenation • The process of adding hydrogen atoms to an unsaturated lipid to increase its saturation level • This process is used at a commercial level to make some oils into a solid (shortening) at room temperature • An example of a product made from hydrogenation is vegetable shortening

13. Rancidity • Rancidity is a form of food spoilage that causes unpleasant flavor and color changes in fats and results from the oxidation of fats • Unsaturated oils are more susceptible than saturated fats because their double bonds are weaker than single bonds • Antioxidants help prevent rancidity by reacting with oxygen before the lipids do

15. Functions of Lipids in the Body • 1. Lipids are a concentrated source of energy and provide 9 Calories per gram • 2. Cell production- Cell walls are made from lipids and proteins. Fatty tissue is deposited around vital organs to help protect them from injury • 3.Temperature regulation- Lipids act as insulators and hold in body warmth • 4. Transport of vitamins- vitamins that are fat-soluble need to combine with fat to be transported throughout the body