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Protein ch6


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Protein ch6

  1. 1. Protein
  2. 2. Protein Basics <ul><li>Amino acids = building blocks of proteins </li></ul><ul><ul><li>20 kinds, but only 9 are essential amino acids (EAA) </li></ul></ul><ul><ul><ul><li>Phenylalanine, valine, tryptophan, methionine, threonine, histidine, isoleucine, leucine, lysine </li></ul></ul></ul><ul><ul><li>EAA needs approx. 11% of total protein intake </li></ul></ul><ul><ul><ul><li>Typical diet supplies 50% as EAA </li></ul></ul></ul><ul><ul><ul><li>Children have higher need for EAA, need high-quality protein in diet </li></ul></ul></ul><ul><li>Each amino acid contains carbon, hydrogen, and nitrogen </li></ul>
  3. 3. Amino Acids <ul><li>Each amino acid contains an “R” group </li></ul><ul><ul><li>Specialized side-group </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Branch-chain amino acids (BCAA) have carbon and hydrogen “R” groups and can be used to make glucose if little or no CHO is consumed in the diet </li></ul></ul></ul><ul><ul><ul><ul><li>Leucine, isoleucine, valine </li></ul></ul></ul></ul><ul><ul><ul><li>PKU (phenylketonuria) – disease caused by inability to convert “R” group of phenylalanine to form tyrosine </li></ul></ul></ul>
  4. 4. Page 211
  5. 5. Amino Acids to Protein <ul><li>Amino acids are connected via peptide bonds </li></ul><ul><ul><li>Dipeptide </li></ul></ul><ul><ul><li>Tripeptide </li></ul></ul><ul><ul><li>Polypeptide </li></ul></ul>
  6. 6. Protein Digestion <ul><li>Denaturation = change in shape </li></ul><ul><ul><li>Heat, acid, alkali, agitation can denature proteins and deactivate them </li></ul></ul><ul><li>Cooking denatures protein </li></ul><ul><ul><li>Makes tough connective tissue softer, easier to chew, swallow, digest </li></ul></ul><ul><ul><li>Kills bacteria </li></ul></ul><ul><ul><li>Inactivates some biologically active proteins </li></ul></ul>
  7. 7. Fig. 6.7
  8. 8. Fig. 6.10
  9. 9. Protein Digestion <ul><li>Stomach – begins digestion of protein </li></ul><ul><ul><li>Acid denatures protein </li></ul></ul><ul><ul><li>Pepsin breaks polypeptides into smaller peptides </li></ul></ul><ul><li>Small intestine - most protein digestion and absorption occurs here </li></ul><ul><ul><li>Pancreatic juice contains proteases which complete digestion of peptides </li></ul></ul><ul><ul><li>Single amino acids and some di- and tripeptides are absorbed </li></ul></ul>
  10. 10. Synthesizing Protein <ul><li>DNA = genetic code for all proteins made by the body </li></ul><ul><li>Change in amino acid  change in protein shape (and function) </li></ul><ul><ul><li>Ex: sickle cell anemia </li></ul></ul>Fig. 6.3
  11. 11. Protein Turnover <ul><li>Protein turnover = constant synthesis and breakdown of protein </li></ul><ul><ul><li>Allows cells to adapt to changes in body circumstances </li></ul></ul><ul><ul><li>Amino acids are easily recycled, so we do not need to eat as much protein </li></ul></ul><ul><li>If amino acid used for energy, made into glucose, or lost due to cell breakdown, waste product ammonia is produced </li></ul><ul><ul><li>Liver turns ammonia into urea which is filtered by kidneys for excretion </li></ul></ul>
  12. 12. Protein Functions in the Body <ul><li>Structure </li></ul><ul><ul><li>Collagen – structural protein found in bones, skin </li></ul></ul><ul><ul><li>Keratin – structural protein found in hair, nails </li></ul></ul><ul><li>Acid-base balance </li></ul><ul><ul><li>Some proteins act as buffers (resist pH change) </li></ul></ul>
  13. 13. Protein Functions in the Body <ul><li>Oncotic pressure </li></ul><ul><ul><li>Presence of protein in small blood vessels attract water back into blood, partially counteracting blood pressure </li></ul></ul><ul><ul><ul><li>If low protein in diet, too much fluid accumulates in tissues = edema </li></ul></ul></ul><ul><ul><ul><li>Hypertension, congestive heart failure, preeclampsia </li></ul></ul></ul>Fig. 6.9
  14. 14. Thinking Time <ul><li>What affect would a drop in pH (more acidic) have on body proteins? </li></ul><ul><li>Why might an elderly adult with a poor appetite have edema in her feet and ankles? </li></ul>
  15. 15. Protein Functions in the Body <ul><li>Hormones </li></ul><ul><ul><li>Thyroid hormone, insulin, glucagon, growth hormone </li></ul></ul><ul><li>Enzymes </li></ul><ul><ul><li>Almost all are proteins or contain protein </li></ul></ul><ul><li>Immune system </li></ul><ul><ul><li>Antibodies are proteins </li></ul></ul><ul><li>Energy </li></ul><ul><ul><li>If low on CHO, liver and kidneys make glucose from BCAA </li></ul></ul><ul><ul><li>If starving, amino acids can be used for energy  muscle and organ wasting </li></ul></ul>
  16. 16. Thinking Time <ul><li>Why does a patient with a poor appetite have a higher risk for infection? </li></ul><ul><li>Why do enzymes and hormones from animal or plant foods not adversely affect our bodies? </li></ul>
  17. 17. Complete vs. Incomplete Protein <ul><li>High-quality/Complete </li></ul><ul><ul><li>Source: animal protein </li></ul></ul><ul><ul><li>Contains all 9 essential amino acids </li></ul></ul><ul><li>Lower-quality/Incomplete </li></ul><ul><ul><li>Source: plant protein </li></ul></ul><ul><ul><li>Missing at least 1 essential amino acid </li></ul></ul><ul><ul><li>Limiting amino acid = essential amino acid missing from protein food or in body </li></ul></ul><ul><ul><li>Complementary protein = plant protein that contains limiting amino acid of another plant protein </li></ul></ul>
  18. 18. Fig. 6.13
  19. 20. Vegetarianism <ul><li>Types of vegetarianism: </li></ul><ul><ul><li>Vegan = strict vegetarian </li></ul></ul><ul><ul><ul><li>No animal products in diet </li></ul></ul></ul><ul><ul><li>Lacto-ovo-vegetarian = consumes milk and egg products but no meat </li></ul></ul><ul><ul><li>Piscevegetarian – consumes fish but no other meat products </li></ul></ul><ul><ul><li>Pollovegetarian – consumes poultry but no red meat </li></ul></ul>
  20. 21. Vegetarianism <ul><li>Health reasons </li></ul><ul><ul><li>Generally lower risk for cardiovascular disease </li></ul></ul><ul><ul><ul><li>Less saturated fat, no or little cholesterol, low sodium </li></ul></ul></ul><ul><ul><ul><li>More fiber, phytochemicals </li></ul></ul></ul><ul><li>Moral/ethical reasons </li></ul><ul><li>Financial reasons </li></ul>
  21. 22. Legumes <ul><li>Legumes provide an excellent source of protein (although incomplete protein) </li></ul><ul><ul><li>Limiting amino acid = methionine </li></ul></ul><ul><li>Also good source of fiber, vitamins and minerals </li></ul><ul><li>Digestive difficulty due to medium-chain length fibers that are fermented by bacteria in large intestine  gas, acid production </li></ul>
  22. 23. Legumes <ul><li>Beano – enzyme formula that may reduce gas production </li></ul><ul><li>Small servings </li></ul><ul><li>Start with split peas, limas, lentils </li></ul><ul><li>Dry bean prep: </li></ul><ul><ul><li>Cook in boiling water for 3 min, turn off heat, cover, soak 2-3 hours, pour off water, use fresh water for cooking </li></ul></ul><ul><li>Canned bean prep: </li></ul><ul><ul><li>Pour off water, rinse well </li></ul></ul>
  23. 24. Soy <ul><li>FDA approved health claim for lowering cholesterol because of soy protein </li></ul><ul><ul><li>25 grams/day </li></ul></ul><ul><li>Sources: tofu, soymilk, soyflour, tempeh, miso, soynuts, edemame </li></ul><ul><li>Isoflavones in soy have possible health benefits: </li></ul><ul><ul><li>Decrease menopause symptoms, osteoporosis risk, some cancer growth </li></ul></ul>
  24. 25. Protein Needs <ul><li>Need to balance protein lost from breakdown (can be determined by urea in urine) </li></ul><ul><li>If growing, pregnant/lactating, or recovering from illness, need more protein </li></ul><ul><li>RDA: 0.8 grams/kg </li></ul><ul><ul><li>8-10% of total kcal intake </li></ul></ul><ul><ul><li>46-56 grams/day needed vs. 65-100 grams actual intake! </li></ul></ul><ul><li>Excess protein intake  amino acids stripped of nitrogen (converted to urea) and carbon skeleton stores as fat </li></ul>
  25. 26. Protein-Energy Malnutrition <ul><li>Marasmus – very inadequate protein and energy intake </li></ul><ul><ul><li>Means “to waste away” </li></ul></ul><ul><ul><li>“ Skin and bones” appearance </li></ul></ul><ul><ul><li>Commonly seen in infants and young children not breastfed, weaned too early, or have water diluting formula </li></ul></ul><ul><li>Kwashiorkor – very inadequate protein, marginal or adequate caloric intake </li></ul><ul><ul><li>Marked edema, especially in belly </li></ul></ul><ul><ul><li>“ The evil spirit the first child gets when the next child is born” </li></ul></ul>
  26. 27. Fig. 6.12
  27. 28. High-protein Diets <ul><li>Pros: </li></ul><ul><ul><li>Provide extra vitamin B6, iron, zinc </li></ul></ul><ul><li>Cons: </li></ul><ul><ul><li>May indicate low plant food intake  decreased fiber, vitamins, some minerals, no phytochemicals </li></ul></ul><ul><ul><li>Associated with cardiovascular disease risk (likely due to saturated fat intake) </li></ul></ul><ul><ul><li>High red meat consumption associated with colon cancer risk </li></ul></ul><ul><ul><li>Extra burden on kidneys to excrete excess nitrogen </li></ul></ul><ul><ul><li>Toxicity from certain amino acids if taken in large amounts (supplements) </li></ul></ul>
  28. 29. Supplementation <ul><li>Amino acid supplements </li></ul><ul><ul><li>Popular ergogenic aids in sports </li></ul></ul><ul><ul><li>Decrease absorption of similar amino acids </li></ul></ul><ul><ul><li>May lead to limiting amino acid situation in body </li></ul></ul><ul><ul><li>Little evidence that they are beneficial to athletes (except for endurance sports) </li></ul></ul>