Protein: Amino Acids

1. Protein: Amino Acids Chapter 6

2. The Chemist’s View of Proteins • Atoms • Carbon, hydrogen, oxygen, nitrogen • Amino acids • Carbon • Hydrogen • Amino group • Acid group • Side group or side chain

3. The Chemist’s View of Proteins

4. The Chemist’s View of Proteins • More complex than carbohydrates or fats • Twenty amino acids • Different characteristics • Essential amino acids • Nonessential amino acids • Conditionally essential

5. The Chemist’s View of Proteins

6. The Chemist’s View of Proteins • Proteins • Peptide bonds link amino acids • Condensation reactions • Amino acid sequencing • Primary structure – chemical bonds • Secondary structure – electrical attractions • Tertiary structure – hydrophilic & hydrophobic • Quaternary structure – two or more polypeptides

7. The Chemist’s View of Proteins

8. The Chemist’s View of Proteins • Protein • Denaturation • Disruption of stability • Uncoil and lose shape • Stomach acid

9. Protein Digestion • Mouth • Stomach • Hydrochloric acid denatures proteins • Pepsinogen to pepsin • Small intestine • Hydrolysis reactions • Peptidase enzymes

10. Protein Digestion

11. Protein Absorption • Transport into intestinal cells • Uses of amino acids by intestinal cells • Unused amino acids transported to liver • Enzyme digestion • Predigested proteins

12. Protein Synthesis • Uniqueness of each person • Amino acid sequences of proteins • Genes – DNA • Diet • Adequate protein • Essential amino acids

14. Protein Synthesis • DNA template to make mRNA • Transcription • mRNA carries code to ribosome • Ribosomes are protein factories • mRNA specifies sequence of amino acids • Translation • tRNA • Sequencing errors

15. Protein Synthesis

16. Protein Synthesis • Gene expression and protein synthesis • Capability of body cells • Protein needs • Dietary influence on gene expression • Disease development

17. Roles of Proteins • Growth and maintenance • Building blocks for most body structures • Collagen • Replacement of dead or damaged cells • Enzymes • Break down, build up, and transform substances • Catalysts

18. Roles of Proteins

19. Roles of Proteins • Hormones • Messenger molecules • Transported in blood to target tissues • Regulators of fluid balance • Edema • Acid-base regulators • Attract hydrogen ions • Transporters – specificity

20. Roles of Proteins

21. Roles of Proteins • Antibodies • Defend body against disease • Specificity • Immunity – memory • Energy and glucose • Starvation and insufficient carbohydrate intake • Other roles

22. Preview of Protein Metabolism • Protein turnover & amino acid pool • Continual production and destruction • Amino acid pool pattern is fairly constant • Used for protein production • Used for energy – if stripped of nitrogen • Nitrogen balance • Zero nitrogen balance or equilibrium • Positive and negative nitrogen balance

23. Preview of Protein Metabolism • Making other compounds • Neurotransmitters • Melanin • Thyroxin • Niacin • Energy and glucose • Wasting of lean body tissue • Adequate intake of carbohydrates and fats

24. Preview of Protein Metabolism • Making fat • Energy and protein exceed needs • Carbohydrate intake is adequate • Can contribute to weight gain • Deaminating amino acids • Stripped of nitrogen-containing amino group • Ammonia • Keto acid

25. Preview of Protein Metabolism • Make proteins & nonessential amino acids • Breakdown of proteins • Keto-acids • Liver cells and nonessential amino acids • Converting ammonia to urea • Liver – ammonia and carbon dioxide • Dietary protein

26. Preview of Protein Metabolism

27. Preview of Protein Metabolism

28. Preview of Protein Metabolism • Excreting urea • Liver releases urea into blood • Kidneys filter urea out of blood • Liver disease: blood ammonia will be high • Kidney disease: blood urea will be high • Protein intake and urea production • Water consumption

29. Preview of Protein Metabolism

30. Protein Quality • Two factors • Digestibility • Other foods consumed • Animal vs. plant proteins • Amino acid composition • Essential amino acid consumption • Nitrogen-containing amino groups • Limiting amino acid

31. Protein Quality • Reference protein • Preschool-age children • High-quality proteins • Animal proteins (complete proteins) • Plant proteins (incomplete proteins) • Complementary proteins • Low-quality proteins combined to provide adequate levels of essential amino acids

32. Protein Regulations for Food Labels • Quantity of protein in grams • Percent Daily Value • Not mandatory • Protein claims • Consumption by children under 4 years old • Quality of protein

33. Protein-Energy Malnutrition (PEM) • Insufficient intake of protein, energy, or both • Prevalent form of malnutrition worldwide • Impact on children • Poor growth • Most common sign of malnutrition • Impact on adults • Conditions leading to PEM

34. Protein-Energy Malnutrition (PEM) • Marasmus • Chronic PEM • Children 6 to 18 months • Poverty • Little old people – just “skin and bones” • Impaired growth, wasting of muscles, impaired brain development, lower body temperature • Digestion and absorption

35. Protein-Energy Malnutrition (PEM) • Kwashiorkor • Acute PEM • Children 18 months to 2 years • Develops rapidly • Aflatoxins • Edema, fatty liver, inflammation, infections, skin and hair changes, free-radical iron • Marasmus-Kwashiorkor mix

36. Protein-Energy Malnutrition (PEM)

37. Protein-Energy Malnutrition (PEM) • Infections • Degradation of antibodies • Dysentery • Heart failure and death • Rehabilitation • Rehydration and nutrition intervention • Add protein slowly

38. Health Effects of Protein • High-protein diets • Heart disease • Animal-protein intake • Homocysteine levels • Arginine levels • Cancer • Protein-rich foods; not protein content of diet • Kidney disease • Acceleration of kidney deterioration

39. Health Effects of Protein • High-protein diets • Osteoporosis • Calcium excretion increases • Ideal ratio has not been determined • Animal protein intake • Weight control • Satiety

40. Recommended Intakes of Protein • Need for dietary protein • Source of essential amino acids • Practical source of nitrogen • 10 to 35 percent of daily energy intake • RDA • Adults = 0.8 grams / kg of body weight / day • Groups with higher recommended intakes • Assumptions

41. Recommended Intakes of Protein • Protein in abundance • Intake in U.S. and Canada • Dietary sources • Serving sizes • Key diet principle – moderation

42. Protein and Amino Acid Supplements • Protein powders • Muscle work vs. protein supplements • Athletic performance • Whey protein • Impact on kidneys • Amino acid supplements • Potential risks associated with intake • Lysine & tryptophan

43. Highlight 6 Nutritional Genomics

44. Nutritional Genomics • New field • Nutrigenomics • Nutrients influence gene activity • Nutrigenetics • Genes influence activity of nutrients • Human genome

45. Nutritional Genomics

46. A Genomics Primer • DNA • 46 chromosomes • Nucleotide bases • Gene expression • Genetic information to protein synthesis • Gene presence vs. gene expression • Epigenetics • DNA methylation

47. A Genomics Primer

48. Genetic Variation and Disease • Genome variation • About 0.1 percent • Goal of nutritional genomics • Customize recommendations that fit individual needs • Single-gene disorders • Phenylketonuria (PKU)

49. Genetic Variation and Disease • Multigene disorders • Study expression and interaction of multiple genes • Sensitive to environmental influences • Example • Heart disease • Single nucleotide polymorphisms (SNPs)