1. Proteins: Crucial Components of All Body Tissues6
Proteins: Crucial Components of All Body Tissues 1

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 2

3. Amino Acids Nine essential amino acids Nonessential 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 3

7. Amino Acids Transamination Conditionally essential amino acid
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 7

9. How Are Proteins Made? Proteins are long chains of amino acids
Peptide bonds join 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 9

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 12

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 14

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 18

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

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 20

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 21

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 23

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 24

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 26

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 27

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

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) 33

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 35

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 36

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

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 39

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 41

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 42

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

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 46

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 47

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