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HNF Review Guide - Exam 2 - HNF Exam 2 Review Guide Lipids...

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HNF Exam 2 Review Guide Lipids_______________________________________________________________________________ _ Lipids: A diverse class of molecules that are insoluble in water Fats: Lipids in diets and food Energy dense: 9kcal/gram ; takes longer to digest (makes us feel more satiated) AMDR: 20-35% of calories should be from fat (20-25% for athletes) Saturated fat: < 7% of total calories; Trans fat: absolute minimum (both heart disease related) Cholesterol: less than 300 mg per day Dietary fiber: 20-30 grams per day Folate: 400 micrograms/day Major energy source used during rest, during exercise when glycogen is depleted Used for energy storage Required for transport of vitamins A, D, E, K Cell membrane structure, never cell transmissions, protection of organs, insulation Visible (butter, cream, mayonnaise) vs. Invisible (baked goods, dairy, meat) Fat replacers in chips, cakes, cookies may cause gastrointestinal distress in large amounts (olestra/Olean) Three Types 1. Triglycerides/Fatty Acids a. Classified by length of carbon chain, level of saturation, and shape b. Carboxyl end (COOH): α-carbon (first) c. Methyl end (CH3): Ω-carbon (last) d. Chain length (short, medium, long) determines digestion, absorption, metabolism e. Saturated fatty acids have hydrogen atoms surrounding every carbon in chain i. Pack tightly together, solid at room temperature ii. Animal fats, butter, lard, some plant oils f. Unsaturated fatty acids i. Do not stack together well, liquid at room temperature
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ii. Plant oils iii. Hydrogen atoms at unsaturated part 1. Cis – on same side of carbon chain; causes chain to bend 2. Trans –on opposite sides of carbon chain iv. Monounsaturated fatty acids lack hydrogen in one part (“one” double bond) v. Polyunsaturated fatty acids lack hydrogen atoms in multiple sites (“more than one” double bond) g. Essential fatty acids: two fatty acids cannot be synthesized by the body and must be obtained from food i. Linoleic acid (omega-6 fatty acid) 1. Found in vegetable and nut oils ii. Alpha-linoleic acid (omega-3 fatty acid) 1. Found in vegetables, canola oil, flax seed, fish oil 2. Phospholipids a. Glycerol backbone, 2 fatty acids, phosphate head b. Soluble in water, transports fat in bloodstream c. Manufactured in our bodies; not required in diet 3. Sterols: Lipids containing multiple rings of carbon atoms a. Essential components of cell membrane, bile, many hormones b. Plant sterols block absorption of dietary cholesterol c. Manufactured in our bodies; not required in diet ------------------------------------------------------------------------------------------------------------------------------- ----------- Digestion of fats Not digested/absorbed easily due to insolubility in water No digestion occurs in watery mouth or stomach; begins in small intestine Some digestion occurs in mouth by lingual lipase Gastric Lipase digests some triglycerides as well in stomach 1. Fat enters small intestine 2. Bile is secreted from gall bladder into small intestine 3. Bile acid and lecithin disperses fat into smaller droplets 4. Pancreatic lipase break fat into 2 fatty acids and a monoglyceride 5. Long Triglycerides build up and combine w/ cholesterol, phospholipids and protein to make lipoproteins for absorption and transport
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