Understanding Proteins and Their Role in Nutrition and Health

1. Protein: Amino Acids

2. Objectives • After reading Chapter 5, class discussion and activities you will be able to: • Describe the role of proteins • Distinguish between complete and incomplete proteins • Identify sources of quality protein • Calculate calories from protein

3. Objectives • Describe protein digestion/absorption • Identify RDA for protein • Discuss health related effects of protein

4. Protein • Essential part of all living cells • Found in animals and plants; Particularly rich in animal foods – meats, poultry, eggs, etc. • Protein is in your skin, hair, nails, muscles, etc. • Made of amino acids – amino acids contain nitrogen, which is necessary for life.

5. Amino Acids p. 163 Fig 5-1

6. Amino Acids • Nonessential amino acids • Body can synthesize • Over half of the 20 AA • Essential amino acids • Body cannot synthesize • Nine (9) • Conditionally essential amino acids • PhenylalanineTyrosine; New Borns

8. Proteins • Peptide bond • Dipeptide • Tripeptide • Polypeptide

9. Proteins • Dipeptide

10. Proteins • Polypeptide (Example: Insulin)

11. Protein shape and function • Amino Acid Sequences

12. Proteins • Protein denaturation • Uncoiling & loss of shape • Therefore, loss of function • Caused by heat, acid, mechanical • Examples: cooked egg, egg whites, curdling of milk, separation of foods with milk or egg (syneresis) p. 176

13. Protein Digestion • Mouth • Mixing, moisturizing • Stomach • HCl • Pepsinogen  pepsin • ProenzymeEnzyme

14. Protein Digestion • Small intestine • Proteases • Intestinal and pancreatic • Peptidases

16. Protein Absorption • Carriers • Transport AA into intestinal cells • Used for synthesis and energy • Capillaries • Carried to liver • Absorption misconceptions • Enzyme/amino acid supplements

17. Protein Synthesis • Delivering the instructions • DNA • mRNA- attaches to ribosome • Protein-making machine

18. Protein Synthesis • Sequencing errors

20. Roles of Proteins • Building material: Building blocks of muscles, blood, skin, bones, teeth; protein matrix=collagen • Growth • Maintenance p. 164-168

21. Roles of Proteins • Enzymes=catalysts p. 165 Fig 5-6

22. Roles of Proteins • Hormones • Switching Machines

23. Roles of Proteins • Regulation of fluid balance • Edema • Acid-base regulation • Acidosis • Alkalosis

24. Transport proteins

25. Roles of Proteins • Immunity: Molecular Memory • Antibodies: Giant protein molecules designed to combat • Antigens: Invading foreign proteins (virus)

26. Roles of Proteins • Source of energy • Gluconeogenesis • No storage source=muscle wasting • “Amino acid pool” • Other roles • Fibrinblood clotting • Opsin—light-sensitive pigment

27. Protein Metabolism • Using amino acids to make proteins=CONDENSATION • Using amino acids to make nonessential amino acids

28. Protein Metabolism • Using amino acids to make other compounds • Neurotransmitters • Using amino acids for energy and glucose • Deamination: AA stripped of N • Ammonia produced

29. Protein Metabolism • Protein turnover • Amino acid pool: supply of AA from food/body; collect in cells & blood; ready for use • Nitrogen balance • Positive nitrogen balance • Negative nitrogen balance

30. Protein Quality • High-quality proteins • All essential AA • Animal proteins=complete • Plant proteins=incomplete • Amino acid composition • Limiting amino acid • Digestibility • Animal vs. vegetable

31. Protein Quality • PDCAAS • Protein digestibility-corrected amino acid score • Reference Protein

32. Protein Quality • Complementary proteins • Two protein foods make up for the lack of certain amino acids in each other when eaten together

33. Food Labels • Quantity of protein • Daily Value • 50 g protein • 10% of a 2000 kcal diet

34. Nitrogen Balance • Determine adequacy of protein intake • N2 In - N2 Out = Nitrogen Balance • N2 In = Protein Intake as Nitrogen • N2 Out = 24 Hour Urine Collection for N2 + Stool, Insensible Losses • Positive Nitrogen Balance • Body excretes less protein than is taken in (Anabolism) • Negative Nitrogen Balance • Body excretes more protein than is taken in (Catabolism)

35. Protein-Energy Malnutrition (PEM) • Marasmus • Slow developing, chronic PEM • Muscle wasting; no body fat • Pluckable hair; dry skin • Kwashiorkor ?????? • Marasmus-kwashiorkor mix

36. p. 171

38. Protein-Energy Malnutrition (PEM) • Infections not protein intake • Dysentery • C-Reactive Protein

39. Health Effects • Conditions Associated with Other Nutrients: • Osteoporosis – Calcium • Heart Disease – Fat • Obesity – Fat/CHO • Cancer - Fat

40. Health Effects • Genetic Associated Diseases • Phenylketonuria • Sickle Cell Anemia • Celiac Disease; Sprue • Liver Disease • Kidney Disease

41. Recommended Intakes • RDA • 0.8 g/kg/day • 10% - 35% of energy intake

42. Review

43. Objectives • After reading Chapter 5, class discussion and activities you will be able to: • Describe the role of proteins • Distinguish between complete and incomplete proteins • Identify sources of quality protein • Calculate calories from protein

44. Objectives • Describe protein digestion/absorption • Identify RDA for protein • Discuss health related effects of protein

45. The End