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248 Cards in this Set
- Front
- Back
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What are the three basic carbohydrates?
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Sugars, Starches, Fiber
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Carbohydrates formula?
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(CH2O)n
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Simple Carbohydrates?
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Monosaccharides
Disaccharides |
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Complex carbohydrates?
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Polysaccharides (starch)
Fiber Glycogen |
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Complex carbohydrates dietary sources?
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Polysaccharides (starch)
Fiber |
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Monosaccharides?
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Glucose
Fructose Galactose |
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Monosaccharides chemical structure?
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(C6H12O6)
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What does hexose mean?
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Monosaccharides are ring structures that contain SIX carbon atoms within each molecule.
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How many bonds can hydrogen form with other atoms?
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Hydrogen can form 1 bond.
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How many bonds can oxygen form with other atoms?
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Oxygen can form 2 bonds.
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How many bonds can nitrogen form with other atoms?
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Nitrogen can form 3 bonds.
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How many bonds can carbon form with other atoms?
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Carbon can form 4 bonds.
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Properties of Glucose?
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- not very sweet
- one of two sugars in all three disaccharides - dextrose or blood sugar -essential energy source |
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Properties of Fructose?
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- Sweetest sugar
-component of sucrose -levulose, "fruit sugar" - sources: honey, fruits, high fructose corn syrup |
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Properties of Galactose?
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-not sweet
-seldom found "free" in nature -usually bound with glucose to form lactose |
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What is a disaccharide?
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Pair of monosaccharides.
Glucose is a component of all three. Formed by condensation. Broken apart by hydrolysis. |
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Three disaccharides?
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Maltose.
Sucrose. Lactose. |
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Maltose
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glucose + glucose
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sucrose
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glucose + fructose
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lactose
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glucose + galactose
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What is a condensation reaction?
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Reactions in which two reactants combine to form a larger product
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What happens in a condensation reaction?
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Hydroxyl group (-OH) from one monosaccharide combines with hydrogen atom from another monosaccharide.
Water is formed. Synthesis reaction. |
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What is a hydrolysis reaction?
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Reaction in which a molecule is split in two.
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What process are hydrolysis reactions a major part of?
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Process of digestion
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What happens in a hydrolysis reaction?
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A hydrogen atom from water is added to one molecule and a hydroxyl group is added to the other molecule.
Water is required for all hydrolysis reactions. |
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Examples of sucrose
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table sugar, powdered sugar, brown sugar, syrups
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What enzyme breaks down sucrose?
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Sucrase
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What is lactose?
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Milk sugar
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What enzyme breaks down lactose?
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lactase
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What is lactose intorlerance?
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People do not make lactase and have trouble digesting (hydrolyzing) lactose in dairy foods
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Lactase deficiency?
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Lack of lactast enzyme
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What is a milk allergy?
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An immune reaction to protein (casein) in milk.
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Lactose Intolerance symptoms?
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Lactose in small intestine remains undigested. Attracts water causing bloating, diarrhea, abdominal discomfort
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Treatment of Lactose Intolerance?
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Eat small amounts of milk/dairy with other foods.
Fermented milk products. Enzyme drops. "Lact-aid milk" |
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What is "lact aid" milk?
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Milk with lactase enzyme added to milk. naturally occuring lactose is converted into glucose and galactose.
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Maltose is an intermediate product of...
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starch breakdown
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Where is maltose found?
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Germinating seeds (bean sprouts/ alpha sprouts) and as malt
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Maltose is a substrate for fermentation process that yields...
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alcohol in beverages and breadmaking
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Polysaccharide?
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many glucose units condense together (hundreds)
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Oligosaccharide?
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3-10 glucose units
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Types of polysaccharides?
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Glycogen.
Starch. Fiber. |
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Polysaccharide food sources?
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Starch and fiber.
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What is starch?
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Plant polysaccharide.
Storage form of energy (glucose) in plants. Long branched/ unbranched glucose chains. major food energy source. |
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What is glycogen?
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Animal polysaccharide.
Storage form of carbohydrate found in muscle and liver. (1200-1400 kcals) Highly branched chains- rapid hydrolysis |
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What is fiber?
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only in plany foods.
polysaccharide not digestible by human enzymes. (some digested by GI tract bacteria) |
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Fiber includes?
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pectins, cellulose, hemicelluloses, gums, mucilages
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Fiber that is a non-polysaccharide
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Lignin
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Fiber benefits and amount in diet?
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Provide GI and cardiovascular benefits.
20-35 gms/day |
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Why is fiber indigestible?
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Humans lack enzyme to break the bond
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What acid is often found in fiber?
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Phytic Acid
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Phytic acid?
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nonnutrient found in grain husks, legummes, seeds.
capable of binding minerals excreted by the body. |
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Minerals excreted by the body?
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zinc, iron, calcium, magnesium, copper
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What is insoluble fiber?
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Not water soluble. Non viscous. Not readily fermintable by GI bacteria
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Food sources of insoluble fiber?
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Wheat bran, whole grain, brown rice, fruits, vegetables
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Action in body/Health Benefits of Insoluble fiber?
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Exercises GI muscles to speed up passage of GI contents
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What is soluble fiber?
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Dissolves in water to form gel. Viscous. Fermentable. Slow passage of food through upper GI tract. Holds moisture in stools
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Food sources of soluble fiber?
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Legumes, oats, fruits (citrus), vegetables
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Action in body/ Health benefits of soluble fiber?
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Forms gel in small intestine containing dissolved glucose and cholesterol/ bile and yields health benefits in vascular system
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Benefits in vascular system due to soluble fiber?
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Slows glucose absorption.Binds with bile/ cholesterol
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Where are carbohydrated digested?
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mouth, small intestine, pancreas, large intestine
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Mouth in carb digestion
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salivary amylase begins starch digestion
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stomach in carb digestion
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No CHO digestion because HCl inactivates salivary enzymes.Fiber is not digested in stomach but lingers delaying gastric emptying, promoting a feeling of fullness
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Small intestine in carb digestion
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maltase, sucrase, lactase
hydrolyze disaccharides |
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pancreas in carb digestion
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pancreatic amylase.
secreted into small intestine; digests remaining starch to individual monosaccharide units |
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Large intestine in carb digestion
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Viscous fibers- fermented into water, gas, short chain FAs
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Viscous fibers action?
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hold water, regulates bowel activity, cause excretion of bound bile, cholesterol, and some minerals
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Within 1-4 hours after a meal what is digested and what is undigested?
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Disaccharides and complex carbohydrates have been digested.
Fibers remain undigested. |
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End-products of carbohydrate digestion?
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glucose, fuctose, galactose
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glucose and galactose is absorbed?
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by active transport
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fructose is absorbed by?
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facilitated diffusion
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All three monosaccharides (glucose, galactose, and fructose) are absorbed...
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from the small intestine to the vascular system (portal vein) to the liver
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In monosaccharide absorption what occurs in the liver?
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Fructose and galactose are converted to glucose
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The liver pumps glucose to?
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into general circulation
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What happens to glucose in carbohydrate metabolism after a meal?
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Blood glucose rises and liver cells link glucose molecules together by condensation reactions
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What is the livers function in carbohydrate metabolism?
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Thel iver stores 1/3 body's total glycogen and releases glucose into the bloodstream
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What occurs when blood glucose falls?
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The liver hydrolyzes glycogen into single molecules of glucose and releases glucose into bloodstream.
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What is used as fuel during exercise?
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Muscle cell glycogen (2/3 total body glycogen)
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What is the total energy available from glycogen?
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1200-1400 kcals
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What are preferred fuels for most of body's cells?
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glucose and fat
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When glucose broken down for energy what is it broken down to and what is released?
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broken down to CO2 and H2O.Heat is released
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How long do kcals from glycogen last?
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only a few days
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What happens when dietary carbohydrate is not supplied and glycogen is depleted as in starvation?
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Problem because cells of the brain, CNS, and RBCs prefer/require glucose as energy source
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Glucongeogenesis?
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synthesis of glucose from non-carbohydrate sources (protein or fat)
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What in the body is glucongeogenesis?what percent?
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Body protein (50%)
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What percent of body fat is gluconeogenesis?
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5%
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What happens when a person does not replenish glycogen stores by eating carbohydrates?
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Body proteins are dismantled to make glucose for brain, CNS, and RBCs
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Protein sparing action?
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action/role of carbohydrate (and fat) in providing energy so protein is spared
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Ketone bodies?
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product of the incomplete breakdown of fat that occurs in gluconeogenesis when glucose is not available
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Ketosis
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fat fragments combine with ketone bodies which accumulate in blood making it more acidic
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The body needs atleast how much carbohydrates/day?
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50-100 gms
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After a meal what steps occur in carbohydrate metabolism?
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Dietary carbohydrates are digested, monosaccharides are absorbed, liver converts fructose and galactose to glucose, glucose is released from liver, blood glucose concentration rises
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What does glucose entering the bloodstream condensed into glycogen replenish?
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Replenishes glycogen stores in liver and muscle
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Excess glucose is converted into...
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fat by the liver and stored in body fat leading to obesity
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Homeostasis?
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maintenance of constant internal conditions by the body's control systems
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Blood glucose?
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regulates hormones
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Hormones regulated by blood glucose levels?
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Insulin (lowers glucose)
Glucagon (raises glucose) Epinephrine (adrenaline) (raises glucose quickly) |
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What is insulin?
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a hormone secreted by the beta cells of the pancreas
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Insulin is secreted by the pancreas in response to?
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Increased glucose
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Primary role of insulin?
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Control the transport of glucose from the blood stream into muscle and fat cells
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Net effect of insulin is to?
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Lower glucose
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What is glucagon?
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a hormone secreted by the alpha cells of the pancreas
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Glucagon is secreted by pancreas in response to?
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Low glucose
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Primary role of glucagon?
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Cause the release of glucose from liver glycogen stores
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Net effect of glucogon?
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Raise glucose
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When is epinephrine released?
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When a person experiences stress
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What does epinephrine do?
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Acts quickly to cause the liver to release glucose from glycogen stores into the bloodstream to ensure all body cells have an energy fuel for emergencies
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Epinephrine is called the ______ hormone?
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fight - or - flight
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-emia
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"in the blood"
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-uria
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"in the urine"
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hyper-
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"an elevated concentration of"
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hypo-
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"too low a concentration of" or "an abnormally low concentration of"
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normo
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"a normal concentration of"
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normoglycemia?
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70-110 mg/ dl glucose
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Two types of diabetes?
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Type 1
Type 2 |
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Type 1 diabetes
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IDDM. failure/lack of insulin production
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Type 2 diabetes
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NIDDM. Obesity. Ineffectiveness of produced insulin
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What does sugar cause?
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Dental caries
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Diets that include whole grains, fibers, vegetables, legumes, and fruits provide what kind of benefits?
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Decrease heart disease and diabetes,and colon cancer. GI health. Weight management
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How much of diet should be complex carbs?
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48%
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ADA recommends how many grams of complex carbs?
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20-35 gms dietary fiber
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What sweetner gives warning to people with PKU?
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Apartame
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Phenylketonuria (PKU)
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genetically inherited disease.
homozygous dominant=no PKU heterozygous people = asymtomatic homozygous recessive= have PKU |
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Health people have enzyme to breakdown phenylalanine into
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tyrosine
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What occurs in people with PKU?
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No enzyme is produced, no tyosine is produced, phyenylalanine is built up
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Lipids
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lipids are a family of compounds characterized by their insolubility in water
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Lipids include:
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TriglyceridesPhospholipidsSterols
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Triglycerides
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Fats and Oils
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TGYs fats
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solid at room tempearature
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TGYs oils
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liquid at room temperature
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Phospholipids
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lecithin
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sterols
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cholesterol
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Lipids in food?
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95% triglycerides stored in body
99% triglycerides |
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Roles of fat in the body
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-chief form of stored energy (starvation/fasting)
-energy for muscular work -component in cell membrane -protects internal organs -raw materials for synthesis of many compounds |
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Roles of fat in diet
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-concentrated energy
-carrier of fat soluble vitamins and aid abosorption -essential fatty acids -palatability of foods (taste and smell) -slows digestive process -contributes to satiety |
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What are basic lipid units?
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Fatty acids
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What are fatty acids?
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-organic compounds
-composed of C chains with -H attached -Acid group (COOH) attached at one end of C chain -Methyl group (-CH3) attached at other end |
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Saturated Fatty acid?
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18 carbon saturated fat;
stearic acid; |
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Monounsaturated fatty acid
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Oleic acid: 18 C; includes Omega carbon; saturated or unsaturated FA
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Polyunsaturated Fatty Acid
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Linoleic acid: 18 C polyunsaturated; saturated or unsaturated FA; Omega Family
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Chemists shorthard to describe # carbon atoms and # double bonds (lipid shorthand nomenclature)
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Examples:
stearic acid: 18:0 Oleic acid: 18:1 Linoleic acid: 18:2 Linolenic acid: 18:3 |
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Omega Nomenclature in FAs
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possible to identify position of first C=C relative to methyl end
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what is the omega carbon atom?
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carbon atom in the methyl group (-CH3) at one end of the FA
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What is the omega number?
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The position of the first C=C relative to the methyl end
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A PUFA with its first double bond three carbons away from methyl end is...
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omega 3 FA
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Why is there an even number of carbon in a fatty acid chain length?
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When FAs are hydrolyzed in digestion, broken apart into 2-C segments
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Long chain fatty acids
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12-24 CMeat and FishOlive Oil
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Medium Chain FAs
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6-10 Ccocoa butter and palm oil
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Short chain FAs
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less than 6 CDairy products
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Degree of Saturation:Saturated FAs
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Fully loaded with HNo C=CButter, lard and palm/coconut oils
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Degree of Saturation:Polyunsaturated FAs
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2 or more C=CLinoleic acid (18 C with 2 C=C)Linolenic acid (18 C ; 3 C=C)Vegetable oils
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Degree of Saturation:Monosaturated FAs
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1 C=COleic acid (18 C with 1 C=C)Olive oil, canola oil, peanuts/peanut oil
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Double bond is the point of
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unsaturation
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Chemical structure of tryglicerides
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95% of lipids in foods99% of lipids in bodycomposed of 3 TGYs linked onto glycerol backcone
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Glycerol + 3 fatty acids =
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Trygliceride + 3 water molecules
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- H from glycerol and hydroxyl group (-OH) from FA =
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H2O (byproduct)
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What does "mixed" tryglyceride mean?
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The fatty acids are of different makes. Some may contain double bonds.
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firmness: more saturated =
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more solid
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oils generally liquid; exception:
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cocoa butter and palm oil (saturated FAs)
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Oxygen causes
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rancidity
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PUFA spoil
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most rapidly
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Saturated more resistant to:
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oxidation/rancidity
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Preventing rancidity:
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seal/refrigerate, add antioxidants or add H to change unsaturated FA to saturated FA (hydrogenation)
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Hydrogenation?
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a chemical process by which hydrogens are added to monounsaturated or polyunsaturated FAs to reduce to number of double bonds (fat becomes more solid)
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Advantages to hydrogenation?
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Protect against oxidation (extend shelf life)
Change texture (vegetable oil--shortening) |
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Hydrogenation disadvantage?
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PUFA become more like saturated FAs - health advantages of PUFAs gone
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Hydrogenation produces:
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trans-fatty acids
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change of shape from cis-FAs to trans-FAs
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increased risk of CVD
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Phospholipids (emulsifying agents) consist of:
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Glycerol backbone, 2 FAs, 1 Phosphate group and N containing compound
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Fatty acids in phopholipds
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fat soluble end
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phosphate group in phospholipids
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water-soluble ends
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constituent of cell membranes in phospholipids
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helps lipids move back and forth across cell membrane into watery fluids on both sides
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phospholipids are good emulsifying agents because:
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fat soluble and water soluble ends help dissolve fats in watery medium
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phospholids are used as emulsifiers in
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the food industry
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phospholipids are found naturally in:
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egg yolk, peanuts, wheat ger, liver, and soybeans
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sterols compounds with:
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multi-ring structure
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sterols multi ring structure includes:
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cholesterol, vitamin D, bile, sex hormones, and adrenal hormones
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cholesterol is both:
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endogenous and exogenous
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Cholesterol is found only in:
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animal foods
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Essential fatty acids:
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linoleic acid
linolenic acid |
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Linolenic acid
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omega 3 FA
-oils -nuts and seeds -vegetables (soybeans) |
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Linoleic Acid
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omega 6 FA
-vegetable oils -poultry fat |
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essential FAs can produce non-essential FAs by undergoing:
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desaturation
elongation |
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desaturation
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addition of double bonds
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elongation
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lengthening of C chain by 2 carbons
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essential fatty acids must make up
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3% of daily energy intake
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Who is at risk for essential FA deficiencies?
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Premature infants, infants/ young children fed fat-free milk/ low fat diets
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Essential FA deficiency symptoms?
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skin lesions and growth retardation
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Challenge with digestion, absorption and transport of lipids?
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Fats are hydrophobic and enzymes to digest fats are hydrophilic
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Where is the major site of lipid digestion/hydrolysis?
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small intestine
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Goal of lipid digestion?
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to hydrolyze TGYS into monoglycerides, free fatty acids, and glycerol
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mouth in lipid digestion
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hard fats melt, lingual lipase (only small amount in adulthood, more in infancy due to large intake of fat)
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stomach in lipid digestion
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gastic lipase (only small amount in adults, little fat digestion)
muscle contractions disperses fat into smaller pieces |
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small intestine in lipid digestion
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fat triggers CCK release: gallbladder releases bile
lipases made by small intestine and pancreas act to digest lipids |
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lipid digestion
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in small intestine, bile emulsifies fat prior to fat hydrolysis
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emulsification of fat by bile: in the stomach
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fat and watery GI juices seperate.
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emulsification of fat by bile when fat enters the small intestine
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the gallbladder secretes bile.
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Bile in emulsification of fat
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has affinity for both fat and water, can bring fat into water
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Biles emulsifying actions:
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convert large fat golublets into small droplets that repel each other
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After emulsification of fat by bile:
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enzymes have easy access to the fat droplets
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triglyceride hydrolysis
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triglyceride and two molecules of water are split, and pieces combine to give two fatty acids and a monoglyceride
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monoglyceride and 2 fatty acids from TGY hydrolysis:
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pass into intestinal cells, but sometime will split more
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lipid absorption:small digested lipids
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absorbed directly into vascular system
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lipid absorption: larger lipids (long chain FAs, monoglycerides, and fat-soluble vitamins)
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absorbed into lymphatic system and then into vascular system
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absorption of small lipids: short and medium chain fatty acids
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water soluble enough to be absorbed from intestinal cells directly into vascular system
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absorption of larger lipids: monoglycerides and long chain FAs
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-not water soluble to be directly absorbed by vascular system-merged into micelles which enter intestinal mucosal cells-inside intestinal cells reassembled into new TGYs-packaged w. cholesterol, phospholipids and proteins into chylomicrons
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micelles
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emulsified fat droplets containing bile, monoglycerides, long-chain FAs
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chylomicrons
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what new TGYs are packaged into with cholesterol, phospholipds and proteins
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chylomicrons are absorbed
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into lymphatic system, thoracic duct (near heart) , vascular system
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After bile has emulsified fat in small intestine: two destinations (enterohepatic circulation)
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1. reabsobed from distal end of small intestine (jejunum) into vascular system; recycled back through liver and gallbladder
2. Bile trapped in soluble fiber in large intestine, excreted from body |
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lipoproteins
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clustersof lipids and proteins that serve as transport vehicles for fats in lymphatic and vascular systems
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placement of phospholipids and proteins ; TGYs and cholesterol in lipoproteins
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phos. and proteins (hydrophilic)- located outside
TGY and cholesterol (hydrophobic)- located inside |
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how do lipoproteins differ?
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by size, density, and amounts of lipid/protein compenents
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lipoprotein chylomicrons
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largest, least dense (>80% TGY) made in intestinal cells
function: transport dietary lipids from intestinal cells to rest of body |
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Very low density lipoproteins (VLDL)
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-made in liver from chylomicron remnants
-TGY removed from VLDL, it becomes more dense, % of components change, VLDV become LDL |
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VLDL function
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transport lipids to various tissues of the body
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Low Density Lipoproteins (LDL)
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Derived from VLDL; composed of cholesterol; LDL=less healthy form of cholesterol (high CVD risk)
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LDL function
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circulate cholesterol throughout the body
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High Density Lipoproteins (HDL)
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smallest and richest in protein made from compenents released from fat cells (primarily cholesterol)
HDL= healthy form of cholesterol (low rish CVD) |
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HDL function
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transport cholesterol from cells back to liver for excretion
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Where is body's primary energy source?
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TGYs in food and body fat
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where is body's fat stored?
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adipose tissue (unlimited storing)
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lipoprotein lipase (LPL)
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hydrolyzes TGYs from circulating lipoproteins into glycerol, FFA, and monoglycerides that enter adipose cells
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inside adipose cells: glycerol, FFAs, and monoglycerides are condensed into
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TGYs
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After a meal, adipose cells:
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store fat when TGY- rich chylomicrons and VLDL pass by
(LPL required for adipose cells to store fat) |
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Body can store how much fat?
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unlimited amounts
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fat supplies __ of energy at rest
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60 %
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hormone sensitive lipase
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- when cells need energy
-inside adipose cells -hydrolyzes TGYs in fat cells |
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glycerol and FFAs enter blood
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and are used as fuel source of cells throughout the body
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1 lb body fat =
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3500 kcals
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If fasting person expends 1750 kcals/day will lose half body fat/day?
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NO
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How much energy needed for brain, cns, and rbcs?
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1/3
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if in prolonged fast, brain and nerve cells derive energy from where?
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2/3 of energy from ketone bodys (fat broken down for energy) BAD
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humans have no excess ____ and ____ for energy?
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proetins/ proteins stores
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what kind of person will survive longer during a forced starvation?
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a person with more body fat
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Relationship between dietary lipids and heart disease?
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raised cholesterol major CVD risk factor (animal in orgin)- not as much as saturated fats/trans fat; HDL vd LDL
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Risks from saturated fats?
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raise LDL- increases CVD risk
animal in orgin |
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Risks from trans fat
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raise LDL; increased CVD risk
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benefits from monounsaturated fats
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decreases CVD risk;
lowers rate of heart disease (olive oil) |
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benefits from polyunsaturated fats
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lowers cholesterol; reduces CVD risk but increases cancer risk
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benefits of omega 3 fats
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decreases CVD risk, prevent blood clots, lowers blood pressure (food not supplements)
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relationship between dietary fats and cancer
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doesnt initiate cancer but does promote. total kcal and obesidy better implyers.
fat from meat more associated with cancer |
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relationship between dietary fat and obesity
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fat contributes 2X many kcals as carbs or protein
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fat recommendations
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total fat <30%
sat fat <10% reduce trans fat reduce cholesterol (300mg/day) eat more omega 3 |
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fat replacers
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carbohydrates/ proteins that replace some/all of the fat in foods lowers kcals
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artificial fat
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olestra
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olestra
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made of sucrose and FAs
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Humans and olestra
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humans dont make enzyme to digest; 0 kcals;
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olestra physical properties
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like fat; may cause abdominal distress; binds with fat soluble vitamins resulting ing excretion additionsl Vit A,D,E,K added to snack foods
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