1. Proteins & Amino Acids Chapter 6

2. Where do we get it? Animal foods –Also provide B vitamins and minerals such as iron, zinc and calcium Plant foods –Also provide B vitamins, iron, zinc, fiber and calcium, but in less absorbable forms Differences in fiber and fat content

3. Protein’s Building Blocks: Amino Acids

4. Variety in Amino Acid Structure

5. Chemist’s View of Proteins  More complex than carbohydrates or fats  Twenty amino acids  Different characteristics  9 essential amino acids  The rest are either nonessential or conditionally essential

7. Chemist’s View of Proteins  Peptide bonds link amino acids  Condensation reactions  Multiple amino acids linked together: polypeptide  Protein: one or more polypeptide chains  Amino acid sequencing and protein structure  Primary structure – chemical bonds  Secondary structure – electrical attractions  Tertiary structure – hydrophilic & hydrophobic  Quaternary structure – two or more polypeptides

8. Primary Structure: Amino Acid Sequence

9. Secondary Structure: Alpha Helix and Beta Sheet

10. Tertiary and Quaternary Structure Tertiary Structure Primary through quaternary structure

11. Protein Shape and Function  Denaturation  Disruption of stability  Uncoil and lose shape  Occurs with exposure to acid or high heat  Mutations: deviations in primary structure

12. Mutations: Sickle Cell Anemia If structure is altered, shape and function may be affected

13. Protein Digestion & Absorption

14. Use of Amino Acids in Body

15. Protein Synthesis  Basis of uniqueness of each person  DNA is the template  Holds the code for amino acid sequences  Structural proteins give us our shape  Enzymes give us our metabolism  Protein synthesis happens in every cell  Diet can influence gene expression  Sequencing errors can affect function

16. DNA Transcription & Translation into Protein

17. Sequencing Errors: Point Mutation

18. Roles of Proteins  Growth and maintenance  Building blocks for most body structures  Collagen  Replacement of dead or damaged cells  Enzymes  Assist in break down, build up, and transform substances  Catalysts: speed up chemical reactions

19. Stepped Art Enzyme A B B A B A New compound Fig. 6-9, p. 181 The separate compounds, A and B, are attracted to the enzyme’s active site, making a reaction likely. The enzyme forms a complex with A and B. The enzyme is unchanged, but A and B have formed a new compound, AB.

20. Roles of Proteins  Hormones  Messenger molecules  Transported in blood to target tissues  Regulators of fluid balance  Hold fluid in the blood  Without these proteins: edema  Acid-base regulators  Function as buffers  Transporters – specificity

21. Insulin: A Protein Hormone

22. Protein Transporter: The Sodium-Potassium Pump

23. Roles of Proteins  Antibodies  Defend body against disease  Energy and glucose  Alternative glucose source during starvation and insufficient carbohydrate intake  Movement: contractile proteins in muscle

24. Energy from Protein

25. Protein Metabolism  Protein turnover & amino acid pool  Continual production and destruction  Need dietary protein to maintain supply  If needed for energy and glucose  Wasting of lean body tissue  Can lower BMR  Extreme deprivation: organ proteins compromised  Prevented by adequate intake of calories, carbohydrates, and fats

26. Protein Metabolism  Making proteins & nonessential amino acids  If essential amino acid needed, body breaks down its own proteins  Rate of protein synthesis may be compromised  Limiting amino acid  Nonessentials can be synthesized  Making other compounds  Neurotransmitters, hormones  Melanin

27. Nonessential Amino Acid Synthesis When a nonessential amino acid is not available from the diet, it can be made in the body by the process of transamination.

28. Protein Metabolism  Making fat  Energy and protein exceed needs  Carbohydrate intake is adequate  Can contribute to weight gain  Creates nitrogenous waste  Nitrogenous waste  In liver – ammonia converted to urea  Filtered out of blood and excreted in urine by kidneys

29. Nitrogenous Waste: Urea  Protein intake and urea production  Production increases in proportion to dietary protein  Water consumption important in high protein diets

30.  Two factors  Digestibility  Animal proteins  Plant proteins  Amino acid composition  Essential amino acid consumption  Nitrogen-containing amino groups  Limiting amino acid Protein Quality

32. Health Effects of Protein  High-protein diets  Heart disease  Increase risk correlated with high animal- protein intake  Differences among protein selections  Cancer  Certain protein-rich foods, not protein content of diet, influence risk  Individuals with kidney disease  Acceleration of kidney deterioration

33. Health Effects of Protein  High-protein diets  Osteoporosis  Calcium excretion increases  High animal protein intake more closely correlated with bone mineral loss  Ideal amount has not been determined, and there are multiple influences on bone health  Weight control  Satiation and satiety

35. Recommended Intakes of Protein  Intake in U.S. and Canada typically adequate or more than adequate  Dietary sources  Serving sizes: what we get vs. what we need  What is a standard serving size of meat?  Key diet principle – moderation  Leave room on the plate for other good stuff!

36. Protein and Amino Acid Supplements  Protein powders  Muscle work vs. protein supplements  Athletic performance  Whey protein  Impact on kidneys?  Amino acid supplements  Potential risks associated with intake  Lysine & tryptophan