1. 1 Chapter 5 Protein

2. 2 Learning Objectives 1. Identify and describe the building blocks of protein 2. List the functions of protein in the body 3. Explain how protein is digested, absorbed, and metabolized 4. Distinguish between complete protein and incomplete protein and list examples of foods that contain each

3. 3 Learning Objectives (cont’d) 5. Explain the potential consequences of eating too much or too little protein 6. State the dietary recommendations for protein 7. Discuss the nutrition and uses of meat, poultry, and fish on the menu 8. Describe soy products, their health benefits, and how to use them on the menu 9. Discuss the advantages and disadvantages of irradiation

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

5. 5 Structure of Protein

6. 6 Part of a Protein Proteins often contain 35 to several hundred or more amino acids Amino Acid Amino Acid Amino Acid Peptide bonds – the bonds that form between adjoining amino acids.

7. 7 Essential & Nonessential Amino Acids Essential or indispensable amino acids Nonessential amino acids One of more may become essential – conditionally essential

8. 8 Proteins Protein fragments with 10 or more amino acids are called: Polypeptides Each of the over 50,000 different proteins in the body contains its own unique number and sequence of amino acids

9. 9 Functions of Protein Acts as a structural component of the body Builds and maintains the body tissues Found in many enzymes and hormones, and all antibodies

10. 10 How Enzymes Work

11. 11 Functions of Protein (cont’d) Act as taxicabs transporting iron and other minerals, fats, and oxygen Maintains fluid and acid-base balance of the blood

12. 12 Functions of Protein (cont’d) Helps blood clot Last resort: provide energy

13. 13 Nutrition Science Focus: Proteins Primary structure of protein: the number of sequence of the amino acids

14. 14 Nutrition Science Focus: DNA

15. 15 Digestion, Absorption, and Metabolism Stomach Hydrochloric acid denatures protein enough so enzymes can enter and do their work Hydrochloric acid also activates pepsinogen to pepsin – an enzyme that splits peptide bonds

16. 16 Digestion, Absorption, and Metabolism Small intestine Proteases split up proteins into short, peptide chains and amino acids Brush border of small intestine makes several peptidases – enzymes that break down short peptide chains into amino acids, dipeptides, and tripeptides As dipeptides and tripeptides enter the intestinal cells, they are split into amino acids Amino acids travel in blood to liver and body cells Amino acid pool provides cells with a supply of amino acids.

17. 17 Protein in Food Animal foods (complete proteins) Plant foods (incomplete proteins) Spaghetti with Meatballs

18. 18 One ounce of meat, poultry, or fish = Protein found in: - 1 egg - ¼ cup cooked dry beans or tofu - 1 tablespoon peanut butter - ½ ounce nuts or seeds

19. 19 Complementary Proteins

20. 20 Protein and Health Eating too much protein has no benefits and may result in: Excessive kcalories Excessive fat if you are eating too much high- fat animal foods Calcium loss High intakes of animal proteins are associated with certain cancers, such as cancer of the colon

21. 21 Protein and Health Eating too little protein can: Slow down the protein rebuilding and repairing process Weaken the immune system Eating too little protein in many developing countries leads to PEM Kwashiorkor Marasmus

22. 22 Dietary Recommendations for Protein RDA: 0.8 g/kg or 0.36 g/lb body weight Nitrogen balance Positive N balance Negative N balance AMDR for protein Children from 1 to 3 years old: 5 to 20% Children from 4 to 18 years old: 10 to 30% Adults: 10 to 35%

23. 23 Ingredient Focus: Meat, Poultry, & Fish Most fish is lower in fat, saturated fat, and cholesterol than are meat and poultry When choosing beef, you will get the least fat from eye of round, followed by top round and bottom round

24. 24 Chicken and Turkey Chicken is twice as fatty as turkey. The skin of chicken and turkey contains much of the bird’s fat White meat chicken and turkey have less fat than dark meat Ground turkey or chicken have varying amounts of fat

25. 25 Ingredient Focus: Meat, Poultry, & Fish Meat is a good source of protein, iron, copper, zinc, and some of the B vitamins Chicken and turkey are rich in protein, niacin, and vitamin B6. Also good sources of riboflavin, vitamin B12, iron, zinc, and magnesium Fish are excellent sources of protein, low in kcalories, and good sources of certain vitamins and minerals

26. 26 Steps to Prepare Healthy Meat, Poultry, & Fish Select a lean cut Use flavorful rubs and marinades Choose a cooking method that will provide a flavorful, moist product and that adds little or no fat to the food Think of how to flavor the dish (i.e. herbs and spices, smoking, etc.) Fish must be cooked very carefully and not overdone. Serve immediately

27. 27 Culinary Science: Denaturation A process in which a protein uncoils and loses its shape Denaturation causes the protein to lose its ability to function

28. 28 Food Facts: Soybeans Tofu Soy sauce Miso Tempeh Textured vegetable protein – TVP Meat analogs Tofu Lasagna

29. 29 Health Benefits of Soybeans If you consume 25 grams of soy protein/day, as part of a diet low in saturated fat and cholesterol, you may reduce your risk of heart disease by reducing blood cholesterol levels Soy may help women promote bone health after menopause – soy’s possible role in breast cancer risk is uncertain

30. 30 Hot Topic: Irradiation

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