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Proteins

Proteins Overview of Protein Body is made up of thousands of proteins Contains nitrogen, carbon, hydrogen, and oxygen Functions Regulates and maintains body functions Provides essential form of nitrogen (in the form of amino acids) Relationship of Essential and Non-essential Amino Acids

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Proteins

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  1. Proteins

  2. Overview of Protein • Body is made up of thousands of proteins • Contains nitrogen, carbon, hydrogen, and oxygen • Functions • Regulates and maintains body functions • Provides essential form of nitrogen (in the form of amino acids)

  3. Relationship of Essential and Non-essential Amino Acids • Example: Phenylalanine    tyrosine (essential non-essential) • But in PKU diagnosed individuals: Phenylalanine    tyrosine (essential NOW essential)

  4. Dietary Protein High-quality complete Low-quality incomplete All-or-none principle in protein synthesis Limiting amino acids Complementary proteins

  5. Limiting Amino Acid CCCCC AAAAAAAA CAR CAR CAR RRRRRR CAR CAR R A A A C is the limiting amino acid in this example

  6. Limiting Amino Acids in Plant Foods

  7. Complementary Protein Food 1 Food 2 Combined CC CCCC AAAA AA CAR CAR CAR RRR RRR CAR CAR CAR

  8. Protein Organization • Order of amino acids in a protein determines its ultimate shape • Protein’s final shape determines its function in the body

  9. Heat/acid/alkaline/enzymes Results in alteration of the protein’s three dimensional structure Denaturation of Proteins

  10. Protein in Foods

  11. Animal Protein • Contribution to our diet • ~70% of our protein intake • Top 5 contributors of protein in U.S. diet: • Beef • Poultry • Milk • White bread • Cheese • Worldwide, 35% comes from animal sources

  12. Provides Protein, minerals, and dietary fiber Contains no cholesterol Limited saturated fats High fiber Time needed to adjust to the higher fiber load Plant Protein

  13. Health and Plant Proteins • Heart healthy • Cancer-fighting • Better glucose control • Nuts as a special focus

  14. Digestion of Protein in the Stomach • Denatured • By cooking and acid in the stomach • Gastrin • Stimulates the release of acid and pepsin • Pepsin • Breaks down proteins

  15. Digestion of Protein in the Small Intestine • Release of CCK (Hormone cholecystokinin – triggers release of pancreatic enzymes and bile) • Pancreatic enzymes: • Trypsin, among others, into the duodenum • Proteins  peptides  amino acids • Ready for absorption

  16. Protein Absorption • Site of digestion • Microvilli surface and within absorptive cells • Many different amino acid transport mechanisms • Active absorption • Amino acids are sent to the liver • Via portal vein

  17. Metabolism of Amino Acids

  18. Functions of Proteins • Building blocks of body components • Fluid balance maintenance • Acid/base balance (contribute to) • Building blocks of hormones and enzymes • Immune function • Gluconeogenesis • Energy yielding (non-preferred source)

  19. Fluid Balance

  20. RDA for Protein • Promotes equilibrium • 0.8 gram of protein / kg of healthy body weight 154 lb. = 70 kg 2.2 kg/lb. 70 kg x 0.8 gram protein = 56 gram protein kg healthy body wt

  21. Protein Balance

  22. RDA for Protein • Increased by ~10-15 grram /day for pregnancy • Endurance athletes • May need 1.2 – 1.7 gram/kg healthy weight • Provide about 8-10% of total kcal • Most of us eat more than the RDA for protein • Excess protein cannot be stored as protein

  23. Is a High-Protein Diet Harmful? • Low in plant foods (fiber), vitamins, phytochemicals • High in saturated fat and cholesterol • Excessive intake of processed red meat is linked with colon cancer • Burden on the kidney • May increase calcium loss in the urine

  24. Malnutrition • Protein-Energy Malnutrition • Marasmus • Seen in hospitalized patients • Kwashiorkor

  25. Protein Calorie Malnutrition

  26. Vegetarian Diets • Why become a vegetarian? • Vegans • Fruitarians • Lactovegetarians • Lactoovovegetarians • Concerns for vegetarians in general • Special concerns for infants and children

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