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Midterm 2 Notes.docx

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University of Guelph
NUTR 1010
Jess Haines

Midterm #2 Notes Fat – part of a larger group of substances called lipids -insoluable in water Different Types of Fat - Triglycerides (95%) – made up of 3 fatty acids o Length – refers to # of C in fatty acids attached to glycerol  Short chain: <6 carbon atoms  Medium chain: 6-12 carbon atoms  Long chain: >14 carbon atoms (most foods we eat*) o Saturation – how they are attached to one another  Saturated: single bond, all saturated w/ hydrogen (sold food)  Monounsaturated: 1 double blond (liquid oils)  Polyunsaturated: >2 double bonds (liquid @ room temp) o Shape  Cis – kinked @ area of double bond  Transpolyunsaturated: straight @ area of double bond - Phospholipids (5%) o Composed of 2 fatty acids, a glycerol backbone & phosphate o Soluable o Help maintain cell membranes - Sterol – ring structure o Cholesterol: most common sterol in diet o Use it to make estrogen & testosterone o Make form of Vit D o Makes vile in liver (helps digest fat) Absorption of Fat occurs primarily in the small intestine - with help of micelles (made up of bile & phospholipds) o transport free fatty acids & monoglycerides to mucosal cells - once inside mucosal cell (intestinal cell) o long-chain fatty acids and mono glycerides are repackaged into triglycerides o triglycerides then packaged w/ protein & phospholipds into chylomicrons Chylomicrons (made in mucosal cells) - type of lipoprotein - “suitcase” – carries triglycerides (outside, protein – inside, fat) - transports triglycerides out of mucosal cell into the lymph then into blood near heart then to body tissues - Chylomicron into tissues, fat either… 1) source of energy for cells 2) make lipid containing compounds in body 3) become part of body fat VLDL -made in liver -very low density lipoprotein -carry triglycerides & bring to cells LDL -low density lipoprotein -made in blood from VLDL -transport cholesterol to our cells ^ cholesterol level HDL -most protein -picks up cholesterol & brings back to liver LDL-cholesterol = <3.5 mmol/L (want low levels) HDL-cholesterol = M, >1.0 … F, >1.2 (want high levels) VLDL = <1.7 Total = <5.2 (sum of LDL, VLDL, HDL) Why do we need Dietary Fat? 1) source of energy - 9kcal/g - fuel source at rest, fuel activity too 2) make lipid-containing compounds in body - essential fatty acids make compounds that regulate body functions 3) become part of body fat - provide protection to body - help maintain integrity of cell membranes - energy storage 4) transport Vit D, E, A, K & texture/flavour of foods Essential Fatty Acids (obtained through diet) 1) Linoleic Acids -omega-6 (double bond in fatty acid chain) -cannot synthesize -metabolized in body to arachidonic acid 2) Alpha-linotenic Acid -omega-3 (double bond on fatty acid chain) -polyunsaturated fat found in leafy green veggies, flaxseed, fish -metabolized in body to eicosapentaeonic acid Acceptable Macronutrient Distribution Range - 20-35% of our total energy should come from fat - <7% of that should be saturated fat o comes from animal sources o associated w/ risk of heart disease o ^cholesterol in our blood, ^ chances it will adhere to arteries - no trans fat recommended Trans fats come from: - some natural, some man-made - fat = prone to oxidation o therefore manufacturers:  air tight containers  preservatives & antioxidants  add hydrogen atoms - Hydrogenation – adding hydrogen atoms o Makes fat more stable when heated o Turns liquid fat to solid o Changes texture - unwanted because: ^ LDL cholesterol and decreases HDL cholesterol & associated w/ heart disease Essential Fats AMDR for omega-6: 5-10% - (11-22g/day) - we meet this - dressings AMDR for omega-3: 0.6-1.2% - (1.3 – 2.6g/day) – we don’t meet this –nuts Monounsaturated Fat - 10% of energy should come from here - “heart-healthy” - decreases LDL cholesterol and displaces saturated fat - HDL cholesterol neutral - Olive oil, canola oil, cashews Dietary Cholesterol – foods of animal origin & little effect on blood cholesterol Margarine Vs Butter Lower saturated Low in essential Lower monounsaturated Low in polyunsaturated Contaminants in fish - include dioxins, PCBS, heavy metals (found in fatty tissues of fish) - predatory fish = ^ levels of mercury (shark, tuna) - safer choices = salmon, shrimp Proteins - contain carbon, hydrogen and oxygen (like CHO & fat) - contains nitrogen (unlike CHO & fat) Why do we need protein? - contribute to cell growth (3-6 days), repair & maintenance - act as enzymes & hormones - play role in transport, immunity, muscle contraction Amino Acids - 9 essential o must be obtained from diet  central carbon molecule (structure)  amine group, acid group, hydrogen, side-chain - 11 nonessential (w/o we couldn’t synthesize protein) o we produce enough to meet our needs o transfer nitrogen-containing group from an essential amino acid to a different amino acid In cells, amino acids can: 1) become part of a growing protein 2) be altered to make other N-containing compounds 3) be broken where: amine group used to build amino acid & remainder is used for energy, converted to glucose or stored as fat (gluconeogenesis) How are proteins made? - peptide bond- 2 amino acids bond, amine group of 1 bond to acid group of another - Insulin – made up of 2 polypeptide chains o Polypeptide chains held together by sulfur-sulfur bonds o Amino acids held together by peptide bonds to make peptide chains o Hemoglobin: 4 polypeptide chains – red blood cells – carries oxygen Mistake in Amino Acid Sequence Structure of protein changes  structure determines function  function changes Sickle Cell Disease - inherited mutation in amino acid sequences (3/1000 births, A. Americans) - Result? Defective production of those chains of hemoglobin - Sickle cells stick together causing clots – leads to bone & organ damage - Vasocclusion: life expectancy is short if you have this Protein Synthesis can be limited by missing amino acids - requires all essential amino acids to be available but a missing one can limit amino acid - Can be enhanced by mutual supplementation o >2 incomplete proteins = complete protein Complete (high quality) – dietary protein with all essential amino acids - animal sources, quinoa, soy beans - 90% digestible Incomplete (low quality) – dietary protein without all essential amino acids - veggie sources & grains - 60-90% digestible Protein Consumed from Animal Sources 70% - North Americans 35% - Worldwide 20% - Africa/East Asia Protein Digestion -mouth -stomach -HCl in stomach breaks apart polypeptide bonds (denatuartion) & stimulates pepsin-enzyme in stomach helps break down long polypeptide chains into shorter ones -short chains move to small intestine -small intestine, 2 enzymes  first set is released by the pancreas  proteases break peptide bonds in polypeptide chains to make even shorter chains -intestinal cell wall – another set of enzymes  peptidases break down small chains to single amino acids -single amino acids are absorbed into the blood, carried into the liver & liver sends them out to the cells as needed What happens when protein intake exceeds requirements? - amino acids stripped of N = deamination - deamination results in two products – (1) N forms ammonia (1) carbon skeleton o liver pulls ammonia out of blood  liver uses ammonia to make urea  kidneys filer urea out of blood  pee - carbon skeleton: o 1) break it down to make acetyl CoA o 2) liver add amino group to make nonessential amino acid o ** no point in taking protein we don’t need** How to figure out Protein Requirements (1)% of total energy intake (AMDR)  10-35% a. why such a wide range? i. Upper end complement ranges for CHO & fat ii. Lower end approximates g/kg recommendation iii. Bodies response varies (2)0.8 grams protein/kg healthy body weight a. male = 95 g/day b. female = 65 g/day c. we eat 1.5x our protein requirements in N.A. d. Exceptions: athletes Why 2 Methods? - adequacy of protein intake in part dependent on energy intake  therefore, if you’re not eating enough energy, the protein will not be used for functions like the immune system Too much protein? 35% + of total energy -^ blood cholesterol -decrease intake of plant foods -increase risk of kidney disease -increase body fat Too little protein? <10% Kwashiorkor  protruding belly caused by severe protein deficiency & moderate energy deficit reversible if caught in time Marasmus  caused by severe protein deficiency and severe energy deficit  “skin & bones”  Canada: elderly, hungry, homeless, diseases Vegetarianiam – restricting foods to plan origin (4% of Canadian
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