1. Protein Chapter 5

2. Introduction Proteins are “of prime importance” Versatile roles: needed for muscle contraction, blood clotting, vision, fighting infections, building new tissue, etc.

3. Chemist’s View Protein Carbon Hydrogen Oxygen Nitrogen  Carbohydrates & Lipids  Carbon  Hydrogen  Oxygen

4. Structure of Proteins About 20 amino acids appear in proteins Are the “building blocks” All share a common chemical “backbone” Also carry a side group which varies

5. Structure of Proteins Amino acids can be linked end to end 2 = dipeptide 3 = tripeptide 10 or more = polypeptide

6. The Chemist’s View of Proteins What determines the shape of polypeptide chains? Different shapes: enable proteins to perform different tasks in the body

9. The Chemist’s View of Proteins (cont’d.) Nonessential amino acids The body can make them for itself Essential amino acids Must be obtained in foods What is a conditionally essential amino acid?

10. Essential Amino Acids Cannot be made by the body Must be obtained from food 9 essential amino acids Conditionally essential A non-essential amino acid can become essential during illness/trauma, premature birth Example: amino acid tyrosine

11. Protein Digestion and Absorption Long peptide chains + enzymes Short peptides + enzymes Tripeptides and dipeptides + enzymes Amino acids

12. Protein Turnover and Nitrogen Balance Protein turnover Continual process in which proteins are made and broken down What are some specific examples? Amino acids needed each day: support new growth and maintenance of cells Nitrogen balance (nitrogen equilibrium) Nitrogen intake equals nitrogen output

13. Nitrogen Balance Nitrogen Balance: N in = N out Healthy adults Positive N balance N in > N out Children & pregnant women Negative N balance N in < N out Fasting or starving Trauma

14. Roles of Body Proteins Structural components Muscle, bones, teeth, tendons, cartilage, blood vessels, etc. Enzymes Catalysts essential to all life processes Some enzymes: break food proteins into amino acids Other enzymes: build long chains of amino acids

15. Proteins as Enzymes Enzymes Are proteins Are catalysts to all life processes Put compounds together and take them apart Are not altered by the reactions they facilitate

16. Roles of Body Proteins Transporters Move substances around the body Hemoglobin: carries oxygen Lipo-proteins: transport lipids Regulators of fluid and electrolyte balance Maintain necessary amounts and types of fluid and minerals in each compartment of the body fluids

17. Fluid & electrolyte balance Body Fluid Compartments Blood vessels In the cells (intracellular) Between the cells (interstitial) Proteins cannot freely pass between compartments but are attracted to water

18. Roles of Body Proteins Regulators of acid-base balance Maintain the balance between acids and bases within the body’s fluids What are the conditions of acidosis and alkalosis? Antibodies Produced when body detects antigens What is immunity?

19. Regulators of Acid Base Acid-base balance Act as buffers in blood & body fluids Gather up extra acid if too much (acidosis) Release acid if too few (alkalosis)

20. Roles of Body Proteins Hormones Some hormones: comprised of proteins Source of energy and glucose When glucose or fatty acids are limited Functions of proteins (Table 5-2)

21. Protein and Health Protein deficiency Slow growth in children, impaired brain and kidney function, weakened immune defenses, and impaired nutrient absorption Conditions Protein-energy malnutrition (PEM) Severe acute malnutrition (SAM): kwashiorkor and marasmus Chronic malnutrition

22. Marasmus Chronic inadequate food intake Children 6-18 months old Look like little old people – just skin & bones Muscles, including heart muscle waste & weaken Impaired brain development

23. Kwashiorkor “Sickness that infects the first child when the second child is born” Occurs between 18 months - 2 years when weaned from breast

24. Protein Energy Malnutrition MarasmusKwashiorkor

26. Protein and Health Protein deficiency What are ways to prevent and treat malnutrition? Protein excess Heart disease Kidney disease Protein and amino acid supplements Read page 130 and decide for yourself about protein and amino acid supplements

27. Protein and Health Protein recommendations and intakes RDA Adult: 0.8 gram per kilogram (2.2 pounds) of healthy body weight DRI Men: 10 to 35 percent of kcalories Women, children, and elderly: 13 to 15 percent kcalories

28. Protein in Foods High-quality proteins Provide adequate amounts of all of the essential amino acids Influenced by: Protein digestibility Amino acid composition Limiting amino acid: essential amino acid Available in the shortest supply relative to the amount needed to support protein synthesis

29. Protein in Foods High-quality proteins Generally derived from animal foods Soy protein Complementary proteins Two protein-rich foods combined to obtain all the essential amino acids in amounts sufficient to support health

33. Protein in Foods Protein sparing Carbohydrate and fat: allow amino acids to be used to build body proteins Absence of carbohydrate and fat Body will use protein to meet energy needs Protein on food labels % Daily Value: reflects quantity and quality