WHAT ARE LIPIDS Presentation prepared by Alice F

WHAT ARE LIPIDS? Presentation prepared by Alice F. Mullis February 2011

DEFINITION of LIPIDS • Lipids are a category of organic compounds that are insoluble in water and have a greasy feel. • Contain mostly carbon, hydrogen and some oxygen.

How do LIPIDS differ from CARBOHYDRATES? • They are not polymers (large molecule that consists of large numbers of small molecular units, which are linked). • Do not provide structure to foods. • Cannot be dissolved in water; they are non-polar thus they are soluble in organic compounds.

Why are Lipids important? • Used to store lots of energy (lipids/fat) – Lipids more difficult to break down (metabolize), but store more energy than carbohydrates • • Form cell membranes (the “skin” of the cell) Cell communication Hormones Many others…

More Lipid information. . . • Lipids are an integral part of our daily diet. • Most oils and milk products that we use for cooking and eating, like butter, cheese, etc. , are composed of fats. Vegetable oils are rich in various polyunsaturated fatty acids. • Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, which are the final degradation products of fats and lipids.

What do Lipids look like? • Each molecule has a “head” with a “tail” – Tail usually consists of two or three strands

Cell Membranes of Lipids • Phospholipids make up cell membranes • Cell membranes are predominantly composed of phospholipids and cholesterol. Cell membranes provide stability to cells and control entry or release of chemicals into or from the cell. – Water is polar – Phospholipids have polar and non-polar ends • So water and phospholipids don’t mix well (one end likes water, the other doesn’t)

What are Lipids? • • Fats Oils Shortening Grease Phospholipids Sterols Cholesterol

GLYCERIDES Molecules that have a glycerol base are called glycerides (a type of lipid). Fatty acids are organic molecules that consist of a carbon chain with a carboxyl group at one end. Fatty Acids + Glycerol = Lipids Most lipids found in foods and in the body are triglycerides.

GLYCERIDES continued… Some glycerides are partially soluble in water such as mono- and diglycerides. These are added to processed foods such as butter and margarine to keep mixtures of water and fats stable.

PHOSPHOLIPIDS • A phospholipid is a glycerol base with two fatty acids and a phosphoruscontaining acid attached. • Important role in the body - help carry fats back and forth across cell membranes. • Important role in food products – help fats stay mixed in water-based solutions like mayonnaise (keeps it from separating).

STEROLS • Sterols are complicated molecules derived or made from lipids. • Sterols include: Cholesterol Vitamin D Steroid hormones

CATEGORIES OF LIPIDS • Saturated – when fatty acids have the maximum number of hydrogen atoms. • Unsaturated – if fatty acid does not contain all the hydrogen atoms it could. • Monounsaturated – fatty acids that have one double bond in the carbon chain. • Polyunsaturated – fatty acids have two or more double bond bends in the fatty chain.

Why be concerned about Trans-Fatty Acids? • Found in many margarines. • A product of hydrogenating vegetable oil. • Humans may not be able to digest the trans-form of these fatty acids & may add build up in blood vessels. • More study is required.

PHYSICAL STATE of LIPIDS • Fats – lipids solid at room temperature • Oils – lipids liquid at room temperature • Melting Point – temperature at which a lipid is completely liquid • Hydrogenation – process of adding hydrogen atoms to an unsaturated lipid to increase its saturation level.

PHYSICAL CHARACTERISTICS of LIPIDS • Three physical characteristics impact the way lipids perform in food products: Melting Point Solidification Point Reaction to Oxygen

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