Lipids PDF

Lipids Sometimes the word is used interchangeably with fat, but it includes both fats and oils Unique characteristic of being insoluble in water In solution they float or roll around in globules Form the cell membrane Chemical Make-up Includes...

Lipids Sometimes the word is used interchangeably with fat, but it includes both fats and oils Unique characteristic of being insoluble in water In solution they float or roll around in globules Form the cell membrane Chemical Make-up Includes: Carbon Hydrogen Oxygen Sometimes phosphorus Primary Role of Lipids in the Body Insulate against the cold Cushion organs against injury Component of every body cell Good source of energy Sense of satiety and slow digestion Carries fat-soluble vitamins (ADEK) Give food pleasing texture Protein sparer Builds cell membranes Source of Lipids Plants — Liquid at room temperature Monounsaturated — oleic acid Polyunsaturated — linoleic acid Animal — Solid at room temperature Saturated 3 Categories of Lipids  1. Triglycerides (95%) (simple lipids) 2. Phospholipids (compound lipids) 3. Sterols (Cholesterol) (derived lipids) Triglycerides (simple lipids) Largest category 95% of all fats found in food and body tissue Most triglycerides in body are stored as fat Fat stored in adipose cells is the body’s largest fuel reserve Energy = 9 kcal/gm Fatty Acids Compounds composed of a chain of carbon atoms with hydrogen atoms attached Short – less than 6 carbons Medium - 6–10 carbons Long - Over 12 carbon Classified as either saturated or unsaturated Saturated – solid at room temperature Unsaturated – liquid at room temperature The more double bonds, the softer at room temperature Saturated Fatty Acid “Saturated” mean carbon chains hold full number of hydrogen atoms Will raise blood cholesterol levels Unsaturated Fatty Acids Monounsaturated fatty acid — One set of double carbon bonds; one point of unsaturation Polyunsaturated fatty acid — Two or more double carbon bonds’ two or more points of unsaturation  Monounsaturated Fatty Acids Have not been associated with any health problems – no effect on serum cholesterol Good fats Example: oleic acid Polyunsaturated Fatty Acids Some studies have been correlated with development of certain reproductive organ cancers Linoleic acid Linolenic acid Two Essential Fatty Acids Obtained from foods in diet Omega 3 — Linolenic acid Anticardiovascular disease nutrient Omega 6 — Linoleic acid Regulates BP, maintains cell membranes, growth, reproduction, maintenance of skin integrity Oxidation of Fatty Acids Oxidation: the process of breaking down fatty acids. Oxygen atoms attach where carbon would attach to hydrogen Hydrogenation Process that infuses hydrogen into fatty acid chain so vacant double bonds become full This type of lipid is called a trans fat  Trans Fats Trans is created when oils are “partially hydrogenated” Phospholipids Look like triglycerides with a phosphorus molecule attached in place of a fatty acid Body produces all the phospholipids it needs NOT used for energy; acts as emulsifier in the body Emulsify — Holds molecules of fat and water together Sterols Contain no fatty acids Cholesterol is most common Only animal foods contain cholesterol High-density (HDL) “good” ○ Made in the liver and small intestine ○ Contain more protein than cholesterol ○ Low-density (LDL) “bad” ○ Denser in fat than protein ○ Carry cholesterol to heart’s arteries  LDL Correlates with an increased risk of cardiovascular disease HDL Correlates with a decreased risk of cardiovascular disease ○ Digestion and Absorption of Lipids ○ Begins in the stomach - gastric lipase enzyme ○ Small intestine is the primary site for digestion and absorption ○ Minor digestion of fat takes place in the stomach through action of lipase enzymes ○ Recommended Daily Intake of fats: Limit to 30% of total calorie intake