1. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. PowerPoint ® Lecture Slides prepared by James Bailey, University of Tennessee 6 C H A P T E R Proteins: Crucial Components of All Body Tissues

2. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What Are Proteins? Proteins: large complex molecules composed of amino acids.  Contain carbon, hydrogen, oxygen, nitrogen  Primary source of nitrogen in our diets  20 different amino acids are used to make proteins

3. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amino Acids Figure 6.1

4. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amino Acids Essential amino acids  Cannot be produced by our bodies  Must be obtained from food  Nine of 20 are essential Nonessential amino acids  Can be made by our bodies

5. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amino Acids: During Stress Some of the Nonessential Amino Acids May Become Essential (need to feed the invalid more protein for healing) Table 6.1

6. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Are Proteins Made? Proteins are long chains of amino acids. They will fold into three-dimensional structures based on their composition. Amino acids are joined to each other by peptide bonds. In the peptide bond, the acid group of one amino acid bonds to the amine group of the adjacent amino acid. Important. Your DNA (genes) code for the structure of each of your proteins!

7. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Are Proteins Made? Transcription: use of the genetic information in DNA to make RNA.  mRNA copies the genetic information and carries it to the ribosome Translation: conversion of genetic information in RNA to assemble amino acids in the proper sequence to synthesis a protein on the ribosome.

8. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Are Proteins Made? Figure 6.4

9. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sequence Determines Function Protein structure has four levels:  (1) Primary structure  Sequential order of amino acids  (2) Secondary structure  Spiral shape due to chemical bonding between the amino acids  (3) Tertiary and (4) Quaternary structure  Further folding into a unique three-dimensional shape that may be globular or fibrous

10. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Levels of Protein Structure Figure 6.6

11. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protein Function Proteins lose shape (denaturation) when subjected to:  Heat  Acids (low pH) and bases (high pH)  Heavy metals  Alcohol Denaturation results in an irreversible loss in protein function

12. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Proteins in the Diet Incomplete protein: does not contain all essential amino acids in sufficient quantities.  Growth and health are compromised  Considered a “low quality” protein Complete protein: contains sufficient amounts of all nine essential amino acids.  Considered a “high quality” protein

13. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Proteins in the Diet Mutual supplementation: combining two incomplete proteins to make a complete protein. Complementary proteins: two protein sources that together supply all nine essential amino acids.  Example: beans and rice

14. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Complementary Food Combinations Figure 6.8

15. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Digestion of Proteins Digestion of proteins begins in the stomach.  Hydrochloric acid breaks down protein structure  Hydrochloric acid activates pepsin Pepsin: an enzyme that breaks down proteins into short polypeptides and amino acids. Note: pepsin is one of the earliest digestive enzymes studied. Pepsin is original name and to honor its place in history they did not update the name to have an ase at the end of its name.

16. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Digestion of Proteins Digestion of proteins continues in the small intestines.  Pancreatic enzymes called proteases complete the digestion of proteins into single amino acids  Indigestible proteins are of lower quality for nutrition Remember: plant proteins are harder to digest than animal proteins.

17. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Summary: Digestion of Proteins Figure 6.12

18. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Functions of Proteins  Cell growth, repair, and maintenance  Enzymes*  Hormones  Fluid and electrolyte balance  pH balance  Antibodies to protect against disease  Energy source (backup, not primary)  *Enzymes are molecules that catalyze reactions. We have discussed digestive enzymes, but they are only one class of these important proteins that help your body catalyze reactions of ALL types.

19. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Much Protein Should We Eat? Protein needs vary depending on:  Activity level (athletes do need more to support muscle.)  Age (young people need more than middle aged people)  Health status (need more for healing than to just maintain health) Example: each day, a sedentary adult requires 0.8 grams protein per kg of body weight.

20. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Much Protein Should We Eat? People who require more protein include:  Children  Adolescents  Pregnant or lactating women  Athletes  Vegetarians

21. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Much Protein Should We Eat? Recommended Dietary Allowance (RDA)  0.8 grams protein per kg of body weight  10–35% of total energy intake should be from protein

22. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protein Balance: a) positive; b) negative; and c) balanced. Figure 6.13

23. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How Much Protein Should We Eat? Table 6.2

24. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Can You Eat Too Much Protein? This only happens in countries where people have lots of money and the food is cheap. The risks of too much protein may include:  High cholesterol and heart disease  Diets high in protein from animal sources are associated with high cholesterol  Possible bone loss  High protein diets may cause excess calcium excretion leading to bone loss

25. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Can You Eat Too Much Protein? The risks of too much protein may include  Kidney disease  High protein diets are associated with an increased risk of kidney disease  Especially for people who may be susceptible to kidney disease

26. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vegetarian Diets Vegetarianism: restricting the diet to foods of plant origin.  There are many versions of vegetarianism – the biggest is poverty (simply insufficient resources to be able to purchase animal foods)  Religion (may restrict all animal foods, or specific animals (e.g. pig, cow)

27. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Some Types of Vegetarian Diets Table 6.5 (1 of 2)

28. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vegetarian Diets Table 6.5 (2 of 2)

29. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Why Vegetarianism? People chose vegetarianism because of  Health benefits  Ecological reasons  Religious reasons  Ethical reasons  Concerns over food safety

30. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Health Benefits of Vegetarianism  Lower intake of fat and total energy  Lower blood pressure  Reduce the risk of heart disease  Reduce the risk of some types of cancer  Fewer digestive problems

31. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Challenges of Vegetarianism  Vegetarian diets can be low in some vitamins and minerals (iron, calcium, zinc, vitamins D and B 12 )  They may also consume insufficient omega-3 and omega-6 fats (ARA)  Vegetarians must plan a balanced and adequate diet  Vegetarians should include complementary proteins

32. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protein-Energy Malnutrition Protein-energy malnutrition: a disorder caused by inadequate intake of protein and energy. There are two common forms:  Marasmus  Kwashiorkor

33. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protein-Energy Malnutrition Marasmus: disease resulting from severely inadequate intakes of protein, energy, and other nutrients. Marasmus symptoms include  Severe wasting of muscle tissue  Stunted physical growth  Stunted brain development  Anemia

34. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protein-Energy Malnutrition Kwashiorkor: disease resulting from extremely low protein intake. Kwashiorkor symptoms include  Some weight loss and muscle wasting  Edema resulting in distention of the belly  Retarded growth and development Kwashiorkor is often seen in children in developing countries.

35. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Genetic Diseases Some genetic diseases can result in protein abnormalities. These diseases are due to a defect in DNA which causes abnormal protein synthesis. The genetic diseases include  Phenylketonuria  Sickle cell anemia  Cystic fibrosis