Dr. Greene Week 8 notes
Dr. Greene Week 8 notes NTRI 2000-002
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This 7 page Class Notes was uploaded by Rachel Ferrell on Sunday March 6, 2016. The Class Notes belongs to NTRI 2000-002 at Auburn University taught by Michael Winand Greene in Fall 2015. Since its upload, it has received 25 views. For similar materials see Nutrition and Health in Nutrition and Food Sciences at Auburn University.
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Date Created: 03/06/16
Rachel Ferrell NTRI 2000 3/9/16-‐3/25/16 Chapter 6: Proteins Overview: • Body is made up of thousands of proteins • Contains nitrogen, carbon, hydrogen, oxygen • General functions: o Regulates and maintains body functions o Provides essential forms of nitrogen (amino-‐acids) • In developed world→diet rich in protein o Issues with this? § Associations between protein intake and mortality § Low protein→less mortality (in ages 50-‐65) § Low protein→more mortality (in ages 66+) • In developing world→ protein deficiencies • Aside from water, protein makes up major part of lean body tissue o About 17% body weight Protein Structure: • Amino-‐acids= building blocks of proteins o Nitrogen bonded to the central carbon o Unique form of carbs/fats • Proteins in body→ made up of only 20 amino acids o 9 are essential § some are limiting (not found in high amounts in food) o 11 are nonessential o New category: Conditionally essential amino acids § Infants or disease states (need more amino acids then usual) • Sequence of amino acids= primary structure o Leads to higher order structure o Leads to specific shape (native conformation) o Shape = function Amino-‐Acid Structure: • Central carbon • Acid group (carboxyl) • Amino group (nitrogen) • Side group (R-‐group)→what makes each amino acid unique • Hydrogen • How are they connected together? Peptide bonds o 2 amino acids→dipeptide o 3 amino acids→tripeptide o Many amino acids→ polypeptide o Some proteins have multiple polypeptide chains Disruption of Normal Protein Structure: • Denaturation= when protein begins to unfold→loses its shape/function o Heat o Strong acids/bases o Heavy metals Protein Primary Structure: • Primary structure→determined by genes/DNA in cell’s nucleus • Info in primary structure is transcribed into messenger RNA (mRNA) • mRNA leaves nucleus→ rough ER→ribosomes→ get translated into proteins Protein Synthesis: • DNA coded instuctions • Copies of codes o Transferred to the cytoplasm(via mRNA) • Amino acids added one at a time o With aid of transfer RNA (tRNA) • Requires energy Central Dogma of Biology: • DNA→RNA→protein How to change Protein Structure: • Genetic alerations • Can change proteins primary structure • Silent mutation= no change in amino acid sequence • Other mutations→ do cause a change in the amino acid sequence, therefore protein/ function o Leads to genetic diseases o Sickle Cell Anemia § Single base substitution § One change in amino acid→changes hemoglobin protein structure § Hemoglobin binds to oxygen in red blood cells § RBC→becomes sickle shaped Digestion of Proteins: • Predigestion→cooking o Heat denatures proteins, softens food • Digestion begins in stomach o 1. Acid (HCL) denatures proteins o 2. Pepsin (enzyme) breaks peptide bonds of proteins reslting in protein fragments § pepsin is released by cells in the stomach and activated by the acidic environment o What controls pepsin and stomach acid release? § Gastrin-‐ a hormone § Released in response to thinking about food and chewing digested food • In the stomach is partially digested proteins and other nutrients→chyme • Movement into small intestine o Release of CCK (hormone)-‐chyme stimulates o CCK causes pancreas to release proteolytic enzymes (cleaving/ breaking proteins such as trypsin and chymotrypsin) o Pepsin inactivation (elevated pH) • Several peptidases are found in the brush border of small intestine • Small peptides (2-‐3 amino acids in length) and free amino acids are absorbed by active transport • Any intracellular peptides are digested by enzymes within cells Amino Acid Absorption • Taken up by capillaries and taken to the liver via the portal vein • Liver o Used as the building blocks for liver proteins o Broken down for energy o Released into blood o Converted to nonessential amino acids, glucose, or fat Are some Individuals Sensitive to Proteins?: • Gluten is a protein found in grains like wheat, rye, and barley that gives baked goods their doughy, elastic structure • Celiac disease= incomplete gluten breakdown in small intestine leaving small peptides and amino acids o Inflammatory response to small peptides and amino acids o Autoimmune response, genetic o Prevalence in US= 1 in 133 o In people with related symptoms= 1 in 56 o To test, do a blood test to test for antibodies. Then, they can do an intestinal biopsy o ***will be a test question on celiacs Infant Digestion of Proteins: • up to 4-‐5 months of age o the GI tract is somewhat permeable to small proteins. Whole proteins can be absorbed o If breastfed, this allows antibodies to be passed from the mother to baby o Reccommendations § Waiting until the infant is at least 6-‐12 months of age before introducing some foods that can cause allergies. Introduce new foods in a step-‐wise manner Functions of Proteins in the Body: • 1.) Producing vital body structures o body is in a state of constant protein turnover= producing and disassembling proteins o What happens with protein inadequacy? § Producing proteins slows down § Muscles, blood, proteins, and vital organs decrease in size § Brain resists breakdown • 2.)Maintaining fluid balance o blood proteins attract fluids o What happens with protein inadequacy § Fluid shifts into tissues→edema (swelling) • 3.) Contributing to acid-‐base balance o Acts as buffers→maintain pH within a narrow range o Keeps blood slightly alkaline (above 7) • 4.) Forming hormones and enzymes o Hormones § Communication between cells o Enzymes § Catalyze reactions in cells • 5.) Transport and Signaling Receptors o Transport § bring nutrients into the cell o Signaling receptors § Communication in the cell • 6.) Contributing to immune function o Antibodies production o What happens with protein inadequacy § Decrease in immune function • 7.) Providing energy o prolonged exercise/ calorie restriction o however, fats/carbs are primarily used for energy § because they are efficient→ it wastes calories to metabolize amino acids for energy • 8.) Forming glucose o Amino acids→converted to glucose when glucose is low o During starvation→ muscle wastes away and edema results from protein breakdown o Glucogenic Amino Acids= used to make glucose (not every AA can be used to make glucose) • 9.) Contributing to Satiety o makes you feel full o can contribute to calorie/weight control Amino Acids Fate in Cells: • breakdown of amino acids o release nitrogen in form of ammonia (NH3) o ammonia converted to urea by liver o kidney converts urea into urine Protein Need: • if you aren’t growing (adults) o only need enough to replace protein you lose daily o What are you replacing? § Normal protein breakdown (protein turnover) o Goal= protein balance • Protein RDA= 0.8 g/kg of a healthy body weight o Ex. body weight= 154 lbs o Divide by 2.2 lb/kg o Then multiply by 0.8g/kg o Answer= 56 g of protein • Food and Nutrition Board→upper range= 35% • In the U.S. o Men→ 100g o women→65g o both eat more protein than needed • Western diet o 70% dietary protein is from animal sources o beef, poultry, milk, bread, cheese • Issue with high protein diet? o Animal meat § No fiber, few vitamins/phytochemicals § High in saturated fat and cholesterol o Red meat/ processed mean→colon cancer o Can put stress on kidneys o Can lose calcium in urine Alternatives to Protein: • Vegetarians= no meat • Semi-‐vegitarians= no red meat • Veagan= no animal products o All use complementary proteins o Nutrient deficiency concerns § Vitamin B12, Iron, Zinc, Calcium, Omega-‐3 • Animal proteins tend to be “complete” or “high-‐quality” o Contains all essential amino acids • Plant proteins tend to be “incomplete” or “low-‐quality” o Low in one or more essential amino acid Plant Sources of Protein: • Nuts→trees • Seeds→ vegetables/flowering plants • Legumes→ pods that have one row of seeds Vegetarian Diet/ Protein: • Grains/nuts→ low in lysine (amino acid) • Vegetables and legumes→ low in methionine (amino acid) • Complementary proteins= combining more proteins together to get all essential amino acids Examples of some Complete Protein in Plants: • Quiona o Grain like crop • Amarantin o Seeds, leafy greens • Soybeans • Buckwheat Protein Consumption: • Can protein consumption be an issue in general? o Gluten sensitivity o Other sensitivities o Food protein Allergies § Immune system mistakes proteins for foreign invaders § 90% of food allergies • soy, peanuts, tree nuts, wheat, milk, eggs, fish, shellfish Protein Calorie Malnutrition: • in the developed world: o diet is typically rich in protein • in the developing world: o protein deficiency is an issue o important to focus on protein diet planning o stunts growth o increase risk of infection • somewhat rare in developed countries o seen in certain populations Protein Energy Malnutrition: • Maramus= starvation/ insufficient protein and calories • Kwashiorkor= enough calories but not enough protein • Diesases commonly found in Africa • What about the US? Protein deficiency? o Only in rural areas; not widespread o Hospital in-‐patients o Long-‐term care residents o Community dwelling adults o Dialysis patients o All have in common?→ older adults +65 Chapter 8: Vitamins: Definition: • 1.) Organic substances needed in only small amounts for the proper functioning of our body • 2.) Essential (body doesn’t make enough or at all) • 3.) Noncaloric Criteria to be Classified as a Vitamin: • the body in unable to synthesize enough of the compound to maintain health • absence of the compound from the diet for a defined period produces deficiency symptoms • can be reversed when the compound is resupplied • a compound does not qualify as a vitamin merely because the body cannot make it Megadoses of Vitamins: • Megadose o Beyond estimates of need o Or not in a balanced diet o 2-‐10 times normal human needs (RDA) o hard to do by eating foods, easy to do with supplements • increases risk for toxicity symptoms • proven useful in treating several non-‐deficiency diseases o Niacin and cholesterol • Issues o Over-‐supplementation can lead to vitamin levels building up over time o Vitamins can be stored within the body o Which ones have potential for reaching toxicity levels? § Fat soluble vitamins→especially Vitamin A Vitamin Preservation: • The riper the food→the more vitamins • Vitamins lost from the time picked to the time consumed o Best to eat as soon as possible after harvest • Water soluble vitamins destroyed by improper storage or excessive cooking o Heat, light, air, cooking in water, alkalinity • Fresh is best, then frozen • How to preserve vitamins in food: o 1.) Freezing→best method o 2.) Blanching→ also works § destroys enzymes that degrade vitamins (heat denatures proteins) Two Classes of Vitamins: • 1.) Fat soluble o vitamins A,D,E, and K o absorbed in chylomicrons o stored in liver and fatty tissue o not readily excreted • 2.) Water soluble o vitamins C and B o absorbed in capillaries o in general not stored to a great degree o excess excreted in urine Vitamin A: • Consists of Retinoids and Carotenoids • Deficiency or toxicity can cause severe problems o Narrow range of optimal intakes • Retinoids o Three active forms of Vitamin A (performed) § Retinol § Retinal § Retinoic acid § Exist only in animal products • Carotenoids o Contained in plant pigments o Phytochemicals-‐ polyphenols o Principle pigment for red, orange, yellow, and green colored fruits and vegetables o Some are precursors to Vitamin A § Can be turned into Vitamin A: Provitamin A o Beta-‐carotene § Carotenoid that can be sufficiently absorbed and converted to retinol Functions of Vitamin A and Carotenoids: • Health of epithelial cells and immune function o Maintains health of epithelial cells that line internal and external surfaces § Lungs, intestines, stomach, bladder, eyes, skin o Serve as important barriers to infection • Vision o Night blindness= vitamin A deficiency disorder that results in loss of ability to see under low-‐light conditions o Vitamin A important for light-‐dark vision and color vision § Retina consists of rods and cones § rods→detect black and white, night vision § cones→ color vision o Carotenoids for vision § Lutein and zeaxanthink in high concentrations in retina • Found in leafy greens • Help prevent macular degeneration • Food sources may help decrease risk of cataracts • Cardiovascular disease prevention o Carotenoids may decrease risk by preventing oxidation of LDL o Recommendation to consume 5 serving a day of fruits and vegetables • Overall growth, development, and reproduction o Vitamin A binds to receptors on DNA to increase synthesis or proteins required for growth o Important for the differentiation and maturation of cells in early fetal growth o Deficiency can cause stunted growth in children • Possible cancer prevention o Potential benefits but also potential risks § Lowers risk of skin, lung, bladder, and breast cancer o Megadose supplements pose potential risk for toxicity § Not recommended o Carotenoids § Decrease risk of lung cancer, oral cancers, prostate cancer in men