Chapter 6 Notes PDF

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Proteins differ structurally from Carbohydrates and Lipids -protein- made up of chains of amino acids that are made based on an individual's DNA Amino Acids (AA) -basic unit of protein -always contains a central C -always has an amino group (-NH2) -Some AA contains S- not found in carbo-hydrates or lipids -20 different AA make a protein Essential Amino Acid -necessary for life and growth -body cannot make AA at all or cannot be made fast enough to meet the need -the unique side chain is the determining factor -for humans- 9 essential AA -must be obtained from food “Non-essential” Amino Acid -does NOT mean that we don’t need the specific amino acid -the AA can be made in the body through a process called TRANSAMINATION -must have the C skeleton -the body can add the amine group (NH2) by transferring it from another amino acid Conditionally Essential Amino Acids -non essential become essential under specific conditions -Tyrosine from phenylalanine -If tyrosine cannot be made -becomes essential General functions of protein -growth, repair and maintenance of body tissues -regulation of body processes -energy-not the best use of protein Growth, repair, and maintenance -pregnancy -growth years -tissues wear out and must be replaced -tissues including the skin, hair, nails, and GI tract lining -regulatory proteins must be replaced -structural components of all organs and tissues Protein Functions -Provide structura; support and enable movement -Collagen- most abundant protein -Actin and myosin- muscle contractions Protein as a source of energy -first priority for protein should be for other function -will be sacrifice to provide energy and glucose if needed -4 kcal/g -approx 58% of AA can be converted to glucose -when necessary, supplies glucose for nervous system and erythrocytes (RBC) Regulatory functions of protein -fluid balance

-hormone, enzyme and antibody formation -pH maintenance -transportation of nutrients -blood clot formation Protein regulates fluid balance -proteins are large molecules -plasma proteins attract water to maintain constant osmotic pressure -structural cellular proteins remain in the cells and attract water -maintain the volume of body fluids to prevent edema -excessive fluid -maintain the composition of body fluids Fluid balance -one cell and its fluids Protein functions -regulate fluids balance -albumin -prevents edema Regulation- hormone, enzyme and antibody formation -many hormones are proteins -hormones are chemical messengers -synthesized in one tissue -released into the blood -have target tissue distant from synthetic site -ex: insulin regulates blood glucose Protein functions -enzymes -speed up reactions -specific -substrate -temperature -pH -can be -catabolic- breaking down -anabolic- building up Antibodies -made of protein -part of the immune system -fight infection -recognize “foreign” material (antigen) such as bacteria and viruses -engulf and destroy potentially harmful foreign materials -specific for the antigen to be attacked Protein function-pH maintenance -act as pH buffers to balance hydrogen ions -acidosis (pH < 7.35) = coma -amine groups bind excess hydrogen ions -alkalosis (pH > 1.45) = convulsions -carboxyl groups donate hydrogens Regulation- transport of nutrients -cell membrane protein

-act as carriers in the cell membranes -transfer compounds from one side of the cell membrane to the other -carry lipids, vitamins, minerals and oxygen in the body -hemoglobin- binds O2 for transport to cells Regulation- more… -blood clot formation -series of proteins must be activated -vision -response to light stimulation- opsin shape changed -stimulates nerve transmission to brain -adaptation to dark -color Protein Digestion: Mouth -no enzymatic breakdown -mechanical-grinding food into particles into smaller pieces -moistened into a paste Protein digestion in the stomach -blous enters the stomach -gastrin stimulates the release of HCI -HCI -denatures the protein -converts pepsinogen to pepsin -pepsin breaks polypeptides into shorter chains Digestion in the small intestine -small intestine-site of most digestion and absorption of proteins -CCK -stimulates the release of pancreatic proteases -pancreatic proteases -break the polypeptides to tripeptides and dipeptides -brush border proteases -break the dipeptides and tripeptides into amino acids Protein digestion -end products -amino acids -di- and tri-peptide -occasionally proteins are absorbed intact -breast milk -food allergies Protein absorption -specific carrier transport AA into the intestinal cell -inside the SI cell: -AA used for energy or -synthesize needed compounds -those not used by SI cells -enter the portal vein to the liver -protein is metabolized in the liver Circulatory system in the digestive tract -water soluble nutrients enter the capillaries for direct transport to the liver -fat soluble nutrients enter the lymphatic system for transport throughout the body before

reaching the liver How are proteins built from amino acids? -20 different amino acids -can be in any order -can have varying amounts of each one -not all must be in every protein -very complex and unique molecules Amino acid (AA) chain -proteins are classified by the number of AA in the chain -peptides: 10 AA -proteins: >50 AA -typically 100 to 10,000 AA linked together How are proteins built from amino acids? -AA are added one at a time -the order of the specific AAs is predetermined Limiting amino acid -an essential amino acid -found in shortest supply relative to the amounts needed for protein synthesis -limits protein synthesis -the EAA found in shortest supply relative to the amounts needed for protein synthesis -limits protein synthesis What controls the synthesis of proteins? -DNA in the cell -all cells have all the “messages” to make proteins -not all parts of the DNA are active in each cell -only proteins that are needed will be made Elements of protein synthesis -DNA: deoxyribonucleic acid -mRNA: messenger ribonucleic acid -tRNAL transfer ribonucleic acid -ribosome: organelle Protein synthesis is regulated by your genes -three steps of protein synthesis -transcription -DNA stores information -DNA unwinds and the sequence is copied by messenger RNA (mRNA) -translation -mRNA translates the information from DNA to an amino acid sequence in the ribosomes -elongation -transfer RNA (tRNA) collects amino acids from amino acid pool -ribosomes build a chain in the proper sequence, continuing until the sequence is finished and the new protein is released Protein synthesis -sequencing errors- can cause altered proteins to be made -ex. Sickle-cell anemia- incorrect AA sequence interferes with the cell’s ability to carry

oxygen The organization and shape of proteins -shape affects function -four levels of structure -primary structure: sequence of amino acid -secondary sequence: folding of protein -tertiary structure: three-dimensional globular shape Quaternary structure: two or more polypeptide chains bond together Protein classification -simple or conjugated -simple- contain only amino acids (AA) -conjugated- also contain other compounds or elements -lipoprotein = lipid conjugated to a protein -glycoprotein = CHO conjugated to a protein -metalloprotein = metal atom conjugated to a protein -native or denatured -native- protein found in living things -denatured- treated with acid, heat or agitation -disrupts the shape of the protein- may destroy its biological activity -does NOT change the order or the numbers of AA -native form important in biological activity -denatured form important in food -more easily digested Denaturing a protein changes the shape -denaturation = unfolding -occurs in the presence of: -heat, acids, bases, salts, and mechanical agitation -alters its function -primary structure is unchanged by denaturing Protein classifications -complete or incomplete -complete- contains ALL of the essential AA in sufficient quantity to support life and growth -are “high quality” proteins -high biological value -takes less of these to meet the body’s need for protein -incomplete- missing sufficient amounts or all or one or more of the essential AA What about foods? -complete proteins- generally supplied by protein from animal sources -expectation: gelatin-lacks tryptophan -incomplete proteins- generally supplied by protein from plant foods -exception: soy protein -foods can supply large amounts of total protein but still be primarily incomplete Protein quality High-quality proteins- contains all the EAA in relatively the same amounts as human beings require -digestibility -animal vs. plant

-digestibility of animal protein is high- 90-99% -plant proteins are less digestible- 70-90% -PDCAAS- protein digestibility-corrected amino acid score -used by the committee on DRI to evaluate protein quality -protein’s AA composition is determined -compared against AA requirements of preschool-age children -reveals the limiting AA -AA score is multiplied by the digestibility percentage to determine PDCAAS Complementary proteins -2 or more proteins whose AAs complement each other -missing ESS from one protein are provided by another protein -together contain all EAA sufficient to support life -combinations of food proteins that have different limiting AA -protein quality of the combination is greater than for either food alone -example: -grains and legumes -animal sources + legumes -animals sources + grains -legumes + grains What are the best food sources of protein? -eggs, meat, fish, soy, and dairy contain significant amounts of protein -a 3-oz serving of cooked meat, poultry, or fish: -provides 21-25g protein -provides about 7g protein/oz -approx size deck of cards -is an adequate amount for one meal -eating a wide variety of foods is the best approach to meeting protein needs -protein supplements -unnecessary and generally not recommended Amino acid metabolism depends on needs of body -most amino acids are sent into the blood to be picked up and used by the cells -maintenance, growth, and healing -converted to glucose for energy (if needed) -not a priority function of protein Deamination removes the anime group from AA -occurs when the amino acid pool reaches capacity -anime group is removed from the AA -ammonia is formed -ammonia is converted into urea and excreted in urine -carbon-containing remnants are: -converted to glucose-gluconeogenesis -converted to fatty acids and stored as triglycerides in adipose tissue Transamination builds nonessential amino acids -anime side chain transferred from one amino acid to a keto acid to form a new nonessential amino acid Protein metabolism -excreting urea -liver releases urea into blood -kidneys filter urea out of blood

-liver disease -kidney disease -protein intake and urea production -water consumption How much protein do you need daily? -healthy adults should be in nitrogen balance -should consume enough to replace what is used every day -individuals in positive nitrogen balance -pregnant woman, people recovering from surgery or injury, and growing children -should consume enough to build new tissue -individuals in negative nitrogen balance -immediately after surgery, fighting an infection, or severe emotional trauma -need to consume enough kilocalories and protein to meet demand You can determine your own protein needs -protein intake recommendations -RDA: 0.8 g/kg daily for adults over 18 -based on healthy weight individual -AMDR: 10-35% of total daily kilocalories -calculation -convert lbs to kg (lbs / 2.2 kg) -176 lbs / 2.2 = 80 kg -kgs x 0.8 g = protein needed -80 kgs x 2.2 g = 64 g protein per day -most men consume approx 100 g/day -women consume approx 70 g/day Special population needs -children < 19 years old -slightly higher needs due to growth -overweight and obese individuals -little difference in needs -The American College of Sports Medicine (ACSM), the Academy of Nutrition and Dietetics, and other experts advocate: -50-100% more protein -competitive athletes participation in endurance exercise or resistance exercise -typically this population eats more and therefore gets additional protein How much protein would meeting the MyPlate provide? -150 lb. male (approx 68 kg): -68 kg x 0.8 g/kg = 54 g protein -each ounce meat approx 7 g protein -each cup milk approx 8 g protein -each grain serving approx 3 g protein -each vegetable servings approx 3 g protein -MyPlate recommendations -meat group: 5-6 ox/d -milk group: 3 svgs/d -grain group: 6 svgs/d -vegetable group” 3 svgs/d Does the MyPlate recommendations provide enough protein for an adult male?

-needed: 54 g -provided: -meat: 25-35g -milk: 16-24g -grain: 18-33g -vegetable: 6-15g -total: 65-107g What happens if you eat too much protein? -may increase risk for heart disease -increase intake of protein sources with high saturated fat -choose a variety of plant sources of protein to decrease risk for heart disease -increase risk for kidney stones -a diet increase animal protein and decrease in carbohydrate- decrease urine pH- can increase the risk of developing kidney stones -increase risk for osteoporosis -increase protein intake with too low calcium intake -increase urinary calcium losses -increase protein diets with adequate calcium (especially from dairy sources) protect bone -too low protein intake can lead to bone loss in elderly men and women -too much emphasis on protein in a diet -displace other important food choices such as whole grains, fruit, and vegetables What happens if you eat too little protein? -protein-energy malnutrition (PEM) -protein is used for energy rather than for its other function in the body -cells lining the GI tract- not sufficiently replaced -decrease digestive function -decrease absorption of nutrients -the immune system is compromised due to malnutrition and cannot fight infection Protein deficiency- protein energy malnutrition (PEM) -one of the most prevalent forms of malnutrition in the world -affects >500 million children -results in >33,000 deaths a year -most common sign is poor growth -may be acute or chronic -acute -chronic PEM -chronic PEM- long term severe food deprivation -low weight for height -”wasting” -acute PEM- recent severe food deprivation -short for age -”stunting” -marasmus- chronic -slow starvation -very thin

-both energy and protein lacking -occurs most commonly in children from 6-18 months Marasmus -body wasting -cessation of growth -conservation of energy -body temperature drops -body movement decreases -child ceases crying -child neglected -deterioration of digestive tract -impairs nutrient absorption and utilization Kwashiorkor -develops quickly -infection such as measles -edema -swollen/bloated belly -protein lacking -yellowish, thinning hair -flaky skin -flabby thighs -generally the result of a diet high in grains and deficient in protein Treatment for PEM -medical and nutritional treatment -can dramatically decrease mortality rate -should be implemented carefully and slowly -step 1: address life-threatening factors -severe dehydration -fluid and nutrient imbalances -step 2: restore depleted tissue -gradually provide nutritionally dense kilocalories and high-quality protein -step 3: transition to foods and introduce physical activity Why people choose a vegetarian diet -people choose vegetarian diets for a variety of reasons -ethical -religious -environmental -health -vegetarians must consume adequate amounts of a variety of foods and should plan meals well Benefits of vegetarian diet -reduced risk of: -heart disease -high blood pressure -diabetes -cancer -stroke -obesity Potential risks of a vegetarian diet

-low intake of key nutrients -protein -calcium -iron -vitamin B12 -zinc -vitamins A and D -omega-3 fatty acids Special populations and vegetarianism -pregnant and lactating women -important to obtain enough E, dairy products and iron -deficiency of B12- psychomotor -supplements needed -children -fe-fortified infant cereal, legumes etc. -vegan infants in danger (B12, Fe, Ca, vitamin D) Potential problems for vegetarians -adolescence -vegan diet may be a problem -decrease E to support growth (shorter, lighter) -decrease bone density, osteoporosis (Ca, vitamin D)...