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This 5 page Class Notes was uploaded by Ticynn London on Friday March 18, 2016. The Class Notes belongs to EXSC 408 at Old Dominion University taught by Kim Baskette in Spring 2016. Since its upload, it has received 21 views. For similar materials see Nutrition in Physical Education at Old Dominion University.
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Date Created: 03/18/16
Dietary Fats • Lipids: HDL, LDL, VLDL • Triglycerides: Actual fats • Phospholipids: Cell membrane • Sterols: Cholesterol, testosterone Primary energy source at rest & during low-intensity exercises • Most concentrated form of energy Triglycerides Consist of 3 fatty acid tails and one glycerol head Comprises nearly 95% of fat in diet “triacylglycerol” – technical term Usually contains a combination of different fatty acids Oils – predominantly poly- and monounsaturated fatty acids • Vegetable oils – 10-13%saturated fatty acids • Coconut oil – 92% saturated fatty acids, 6% monounsaturated, and 2% polyunsaturated Fatty Acids Chains of carbon & hydrogen with carboxyl group (COOH) at one end • Length varies from 4-24 carbon bonds Saturated fatty acids • Contain single carbon bond • From animals • Solid at room temp Unsaturated fatty acids • 1 or more double bonds • Plant source • Liquid a room temp and solid at cold temp Monounsaturated • One double bond Polyunsaturated • Two or more double bonds We consume about 16-18 carbon bonds Unsaturated Formation • Cis – groups on same side of double bonds - allows fatty acids to bend - facilitates movement across cell membrane • Trans – groups on opposite sides of double bonds - produced synthetically though “hydrogenation” Trans Fat Hydrogenation • Used in commercial food processing to make liquid oils more solid • Double bonds on unsaturated fat broken, and hydrogen atoms added • Can be full or partial saturation Polyunsaturated • Double bond between carbons counted from last carbon in chain farthest from carboxyl group carbon • Omega-3, 6 and 9 Omega-3 fatty acids Alpha-linoleic acid (ALA) • Essential fatty acid; cannot be manufactured by body • Ex: soy, canola, and flaxseed oils, leafy green veggies, fatty fish, and fish oil Eicosapentaenoic acid (EPA) • Marine (oily) fish- (salmon, mackerel, sardines) Docosahexaenoic acid (DHA) • Main component of membrane phospholipase • Same sources as EPA Omega-6 fatty acids Linoleic acid: not manufactured by the body • Essential fatty acid in many vegetable oils Arachidonic acid- found in animals • Precursor to prostaglandins & other related hormone compounds Recommended ratio: omega-6: omega-3 – 4:1 • Typical Western diets are 15:1 (animal fats) Oleic acid- Omega-9 monounsaturated fatty acid (ex. Olive oil) • Helps reduce the risk of heart disease if substituted for saturated and trans fat Sterols & Phospholipids Comprise remaining 5% of fats in foods Sterols- ex: cholesterol, cortisol, vitamin D, and sex hormones • Group of fats with four ring structure • Contains one or more OH groups & no carbonyl (=C=O) or carboxyl (COOH) groups Cholesterol – animal foods • Cell membrane component Phospholipids • Structure similar to triglycerides but includes phosphate in glycerol head with only 2 fatty acids • Structural component of all living tissues Digestion of fats Occurs primarily in small intestine Mix with bile salts & digestive enzymes before crossing intestinal cell membranes Pancreatic lipase - breaks down large fatty acids • Monoglycerides and free fatty acids Absorption of fats Exogenous pathway • Cross into mucosal cells through passive diffusion • Monoglyceride resynthesized into triglycerides Short- (4 carbon) & medium- (6-10 carbon) absorbed as free fatty acids • Free fatty acid chains is bound to albumin in the bloodstream (non dissolvable) Majority of dietary fats are long-chain fatty acids Triglyceride incorporated into chylomicron molecule • Large transport molecule containing fats Chylomicron composition (lipoprotein) • Triglycerides – 92% • Phospholipids – 12% • Cholesterol – 3% • Proteins – 2% Chylomicrons released slowly into lymphatic vessels & enter bloodstream • Present in bloodstream – 1.5 hours after meal • Triglyceride metabolized by lipoprotein lipase - fatty acids and glycerol absorbed by adipose and muscle tissue cells - cleared from bloodstream after 12hr fast Chylomicron remnants - formed after removal of triglyceride core • Taken up by the liver and removed from circulation Storage of fats Esterification • Fatty acids reformed into triglycerides for storage in adipocytes • Stimulated by insulin and mediated by LPL Stored as subcutaneous & visceral fat & intramuscular triglycerides • Ex: myocardial and type I skeletal muscle • Ex: Anhydrous Efficient storage form of energy Metabolism of fats Lipolysis - Fats mobilized from storage & broken down into glycerol & fatty acids • Catalyzed by hormone-sensitive lipase (HSL) • Post absorptive state, fasting, starvation, stress, and exercise Fatty acids & glycerol circulate in blood & taken up by appropriate tissues • Most of glycerol taken up by liver – metabolized to glucose or reassemble into triglycerides • Free fatty acids – bound to carrier protein and transport in blood Fatty acids distributed to other tissues in body and metabolized • Utilization dependent on number of receptor sites & transport mechanisms in cell membrane • Ex: heart muscle cells have higher capacity fat utilization vs. Type I muscles fiber which are higher than Type II Provide a high source of energy but metabolic process complex and slow Metabolism of intracellular fats Fatty acid chains converted to fatty acyl-CoA • Occurs in outer mitochondria membrane Fatty acyl-CoA translocate to inner mitochondrial matrix • Co-A removed and fatty acid attached to carnitine molecule • Re-joined with CoA once inside mitochondria • Catalyzed by carnitine acyl transferase enzymes Increased uptake in cells with large number of well-developed mitochondria Beta-oxidation: • Fatty acid chains converted to acetyl-CoA & enters Krebs cycle • Each acetyl-CoA – generates 10 ATP; 1 NADH and FADHR • Ex: Palmitate- ice carbon fat: 8 acetyl CoA and 80 ATP Ketones Conversion of acetyl-CoA to ketone bodies • Acetoacetate, acetone, & Β-hydroxybutyrate Up to 185g of ketones produced daily by liver • Supplies 2-6% of body’s total energy needs after overnight fast • Plasma levels – <0.05 MO/L Accelerated fatty acid oxidation • Increases production of ketones • Ketosis Plasma levels – > 0.06 MO/L Ketoacidosis – associated with diabetic coma and death Starvation, restriction of carbs, impaired metabolism; Ketones become the primary source of energy for brain (76 weeks, 70% of energy) Restriction of carbs in diet • Gluconeogenesis occurs in first 2-3 days • After 3 days, glucose primarily manufactured from glycerol Affect on athletic performance • Low glycogen stores • Inability to sustain training and or train at high intensities
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