Proteins

1. Proteins

2. Protein • vital to all cell structure • human body contains 10,000 – 50,000 different kinds • 1000 have been studied • versatile, unique, and have specific functions • contain carbon, hydrogen, oxygen and nitrogen (amino) • amino acids are the links in protein chains

3. Amino Acids Side group varies Amino group • all 20 have the same basic structure • distinction is due to the variation in the side group • more than ½ are nonessential • 9 essential • proteins provide these Acid group

4. human insulin: 2 polypeptide chains for a total of 51 amino acids Proteins • links of varying sequences of amino acids form thousands of different proteins • peptide bond links amino acids together • most are several dozen to several 100 amino acids long • condensation reactions connect amino acids • 2 amino acids = dipeptide

5. Protein Shape • to function properly a protein must maintain it’s shape • hollow balls to carry or store materials • rodlike such as those found in tendons

6. Protein Denaturation • heat, acid, chemicals can cause proteins to lose their shape • lose their ability to function

7. Protein Digestion • mouth • crushed and moistened for ease of swallowing • stomach • hydrolysis • hydrochloric denatures allowing enzymes to attack the peptide bonds • pepsin (active form of enzyme pepsinogen) cleaves protein into smaller polypeptides and amino acids

8. Protein Digestion • small intestine • proteases hydrolyze into short peptide chains • peptidase enzyme further breaks chains down to amino acids

10. Protein Absorption • amino acids and some dipeptides are transported into intestinal cells • amino acids may be used for energy once inside the intestinal cells

11. Protein Synthesis • protein function is determined during synthesis • genes determine the amino acid sequences that make up unique protein

12. Protein Synthesis • DNA forms a template for the amino acids • amino acids are lined up to make the protein • genetic errors can alter the sequence resulting in consequences such as sickle-cell anemia

13. Roles of Proteins • building and maintenance • found in most body structures such as skin, tendons, membranes, muscle, organs and bones • enzymes • proteins that enhance chemical reactions • hormones • proteins that regulate body processes • some hormones are proteins

14. fluid balance • maintain the volume and composition of body fluids • acid-base balance • act as buffers • transportation • lipoproteins transport lipids • hemoglobin transport oxygen • antibodies • protein molecules used in defending out body against invading pathogens

15. energy • can be sacrificed to provide energy if needed • other functions • vision, blood clotting

16. Protein Metabolism • protein turnover • constant making and breaking of proteins • frees amino acids to “amino acid pool” • can be used to make body proteins • nonessential amino acids can be made from other amino acids

17. amino acid pool • stripped of nitrogens and made available for energy • deamination • can make other compounds such as melanin • make fat • amino acids are deaminated, nitrogen is excreted, carbon is converted to fat and stored • protein-rich foods can cause weight gain

18. Protein in Foods • protein quality • determined by child’s growth and adults health maintenance • influenced by digestibility and amino acid composition

19. digestibility • dependent on source • 90-99% of animal proteins • 70-90% plant proteins • amino acid composition • amino acids are necessary to make proteins • body makes whole proteins only • all have to be there at the same time • dismantle a protein to access an unavailable essential amino acid

20. PDCAAS • protein digestibility-corrected amino acid score • measure of protein quality • scientific formulas that take into account proportion of amino acids and relative digestibility of protein • used for food labeling

21. Food Labels • protein content must be stated in grams • % Daily Value not mandatory unless • food makes a protein claim • intended for children < 4 yrs old • includes quantity and quality

22. PEM • protein-energy malnutrition • deprivation of protein, energy, or both • most often children • 500 million children • 33,000 die /year

23. PEM • inadequate food intake • poor growth in children • weight loss and wasting in adults • acute PEM • recent severe food deprivation • chronic PEM • long-term food derpivation

24. Marasmus • chronic PEM • person is starving • Kwashiorkor • acute PEM • sudden or recent food deprivation

25. Malnutrition Worldwide

26. Health Effects of Protein • excess protein as well as too little protein can affect health • food rich in protein is often rich in saturated fats • difficult to separate the risk factors

27. Protein Intake • continuous breakdown of protein • some protein is lost • cannot store amino acids • protein replacement is dependent on dietary protein • essential amino acids • source of nitrogen • 200-700 kcalories = 50-175 grams

28. Protein Intake • RDA is 0.8 grams/kilogram of body weight • enough for repair • higher for infants and children and pregnant women • enough for growth

29. Protein and Amino Acid Supplements • not necessary, may even be harmful • muscle work builds muscle • expensive and less digestible • amino acids do not occur singly in food • body can’t handle high concentrations or unusual combinations

30. 2 exceptions • lysine • may suppress herpes infections and appears safe • tryptophan • effective for pain relief and sleep • experimental