Proteins: Crucial Components of All Body Tissues

1. 6 Proteins: Crucial Components of All Body Tissues

2. What Are Proteins? • Proteins: large, complex molecules found in cells of all living things • Dictated by genetic material (DNA) • Contain carbon, hydrogen, oxygen, nitrogen • Made from 20 different amino acids The Building Blocks of Proteins

3. Amino Acids • Nine essential amino acids • Cannot be produced in sufficient quantities to meet physiological needs • Must be obtained from food • Nonessential amino acids • Can be synthesized in sufficient quantities

7. Amino Acids • Transamination • Transfer amine group from an essential amino acid to a different acid group and R group • Conditionally essential amino acid • Nonessential amino acid becomes essential • Phenylketonuria (PKU): tyrosine becomes a conditionally essential amino acid that must be provided by the diet Deanimation/Transanimation

9. How Are Proteins Made? • Proteins are long chains of amino acids • Peptide bondsjoin amino acids together • Gene expression is the process by which cells use genes to make proteins • Gene: segment of deoxyribonucleic acid (DNA) that serves as a template for the synthesis (expression) of a particular protein

12. How Are Proteins Made? • Transcription: messenger RNA copies the genetic information from DNA • Translation: the genetic information in RNA is converted into the amino acid sequence of a protein

14. How Are Proteins Made? • Protein turnover • Existing proteins are degraded to provide the building blocks for new proteins • Amino acid pool includes amino acids from food and cellular breakdown • Protein organization determines function • Sequential order of the amino acids • Spiral shape from twist in amino acid chain Protein Synthesis

18. Protein Denaturation • Proteins uncoil and lose their shape • Damaging substances: heat, acid, base, heavy metal, alcohol • Protein function is lost • Denatured enzyme • High fever • Blood pH out of normal range • During digestion

19. Protein in the Diet • For protein synthesis, all essential amino acids must be available to the cell • Limitingamino acid • Essential amino acid that is missing or in the smallest supply • Slows down or halts protein synthesis • Inadequate energy consumption • Limits protein synthesis

20. Protein in the Diet • Incomplete protein (low quality): insufficient essential amino acids • Does not support growth and health • Complete protein (high quality): sufficient amounts of all nine essential amino acids • Derived from animal and soy protein

21. Protein in the Diet • Mutual supplementation: combine two or more incomplete protein sources to make a complete protein • Complementary proteins: two or more foods are combined to supply all nine essential amino acids for a complete protein

23. Protein Digestion • Protein digestion begins in the stomach • Hydrochloric acid denatures protein strands and activates pepsin • Pepsin: enzyme breaks down proteins into short polypeptides and amino acids • Gastrin: hormone controls hydrochloric acid production and pepsin release

24. Protein Digestion • Digestion continues in the small intestine • Pancreatic enzymes (proteases) complete protein digestion • Special sites (small intestine) transport amino acids, dipeptides, tripeptides • High doses of individual amino acid supplements can lead to amino acid toxicity and deficiencies Protein Digestion

26. Protein Quality • Methods for estimating protein quality • Chemical score • Protein digestibility corrected amino acid score (PDCAAS) • Animal protein and many soy products are highly digestible (90% absorption) Protein Absorption

27. Functions of Proteins • Cell growth, repair, maintenance • Enzymes and hormones • Fluid and electrolyte balance • Acid−base balance • Immune system • Energy source • Nutrient transport and storage

31. Protein Adequacy • Nitrogen balance determines protein needs • Positive nitrogen balance • Negative nitrogen balance • In nitrogen balance Nitrogen Balance

33. RDA for Protein • RDA = 0.8 g per kg body weight per day • Recommended percentage of energy is 10−35% of total energy intake • Protein needs are higher during growth and development (children, adolescents, and pregnant/lactating women)

35. Too Much Protein Can Be Harmful • High cholesterol and heart disease • Animal-protein-rich diets are associated with high blood cholesterol levels (saturated fat) • Contribution to bone loss • High-protein diets increase calcium excretion and possibly lead to bone loss

36. Too Much Protein Can Be Harmful • Kidney disease • High protein intakes are associated with an increased risk among susceptible individuals • People with diabetes have higher rates of kidney disease and may benefit from a lower-protein diet • Maximum of 2 g of protein per kilogram body weight each day is safe for healthy people Fat Synthesis from Excess Protein

37. Protein Sources • Meats • Milk-based products • Soy products • Legumes • Whole grains • Nuts • Quorn

39. Vegetarian Diets • Vegetarianism: restricting the diet to foods of plant origin • People chose vegetarianism for: • Health benefits • Ecological reasons • Religious reasons • Ethical reasons • Concerns over food safety

41. Health Benefits of Vegetarianism • Lower fat and total energy intake • Lower blood pressure • Reduced risk of heart disease • Fewer digestive problems • Reduced risk of some cancers • Reduced risk of kidney disease, kidney stones, and gallstones

42. Challenges of Vegetarian Diets • Can be low in some nutrients • Associated with disordered eating • Varied and adequate diet planning • Soy and complementary proteins • Vegetarian Food Guide Pyramid • Special attention to vitamins D, B12, and riboflavin (B2); minerals zinc and iron

44. Protein-Energy Malnutrition • Protein-energy malnutrition: caused by inadequate protein and energy intake • Common forms: • Marasmus • Kwashiorkor

46. Marasmus • Grossly inadequate energy and nutrient intake • Consequences of marasmus: • Wasting and weakening of muscles (heart) • Stunted brain development and learning • Depressed metabolism • Stunted physical growth • Deterioration of the intestinal lining (anemia) • Severely weakened immune system • Fluid and electrolyte imbalances

47. Kwashiorkor • Disease resulting from low protein intake • Kwashiorkor symptoms include: • Some weight loss and muscle wasting • Retarded growth and development • Edema resulting in distention of the belly • Fatty degeneration of the liver • Loss of appetite, sadness, irritability, apathy • Skin problems and hair loss

48. Genetic Disorders • Numerous disorders are caused by defective DNA • Genetic disorders include: • Phenylketonuria • Sickle cell anemia • Cystic fibrosis