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Chapter Five

Chapter Five. The Proteins & Amino Acids. I. What Proteins Are Made of. Amino Acids Amine Group Acid Group Side Group All protein molecules contain nitrogen atoms. Nine amino acids Cannot be made (synthesized) by the body from other amino acids

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Chapter Five

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  1. Chapter Five The Proteins & Amino Acids

  2. I. What Proteins Are Made of • Amino Acids • Amine Group • Acid Group • Side Group • All protein molecules contain nitrogen atoms.

  3. Nine amino acids Cannot be made (synthesized) by the body from other amino acids Protein foods must be eaten daily that contain these amino acids 11 amino acids Can be made from other parts Nitrogen (other proteins) Backbone (carbohydrates and fats) A. Essential & Nonessential Amino Acids

  4. Cont’d • Some amino acids are considered essential at different stages of life or in states of illness. • “Conditionally essential”

  5. B. Synthesis of Proteins • Peptide bond • Between amino end & acid end

  6. B. Synthesis of Proteins • Different places along the chain of amino acids & side chains may be attracted to others

  7. B. Synthesis of Proteins • Strand coils & folds back on itself, giving the protein a distinct shape. • Shapes of proteins affect how they are used in the body

  8. C. Denaturation of Proteins • First step in its destruction • Excess heat, alcohol, acids or salts of heavy metals can damage the body’s proteins • Stomach acid opens up the protein’s structure and permits digestive enzymes to act upon the protein.

  9. II. The Functions of Proteins • Growth & Maintenance • Dietary protein ensures that amino acids are available to build the proteins needed for new tissue. • Nearly all cells are constantly replaced, requiring protein.

  10. B. Enzymes • Proteins such as enzymes are catalysts that help chemical reactions take place. • Each enzyme is specific for a particular reaction.

  11. C. Hormones • Some hormones, but not all, are proteins • Hormones signal the appropriate enzymes to act.

  12. D. Antibodies • Formed in response to foreign substances in the body. • Each antibody is specific to one foreign substance. • Once an antibody is made for the substance, the body develops immunity to that substance.

  13. E. Fluid Balance Fluid Balance: • Proteins help regulate the quantity of fluids to help maintain fluid balance. • Cells and the spaces between cells must contain a constant flux of and amount of fluid. • Water can diffuse freely in and out of a cell; proteins can not

  14. F. Acid-Base Balance • Normal body processes produce acids & bases that must be excreted • pH: concentration of hydrogen ions • Acids: release hydrogen ions • Bases: accept hydrogen ions • Acid-Base Balance: equilibrium between acids and bases in body

  15. Cont’d • Blood proteins act as buffers for acid-base balance. • Buffers: can give up or add extra hydrogen to maintain balance • Acidosis or alkalosis may occur if acid-base balance is upset

  16. G. Transport Proteins • Move nutrients and other molecules in and out of cells • Turn on and off • Hormones do the switching • Move substances from one organ to another • Lipoproteins • Vitamins and minerals

  17. G. Energy • Protein may be sacrificed to provide energy if insufficient carbohydrate and fat are eaten. • Amino acids are degraded for energy. • Amino acids will only make proteins if carbs and fat are providing protein-sparing energy. • Protein-sparing: Leave amino acids alone to make proteins

  18. III. Digestion & Absorption of Protein • Begins in the stomach with denaturation • Breaks into dipeptides, tripeptides and free amino acids into small intestine

  19. HOW BODY HANDLES PROTEIN • Amino acids taken up by cells • Protein synthesis takes place • If “non-essential” amino acid is missing, the body can make it • If “essential” amino acid is missing, the protein synthesis stops and all of the amino acids in place are dismantled and the protein is not made

  20. IV. Protein Quality • A measure of the essential amino acid content of a protein relative to the essential amino acid needs of the body • Biological value (BV) – how well supports nitrogen balance • Reference protein – egg white protein, the standard to which other proteins are compared = 100 score

  21. Complete protein: contains all the essential amino acids in the right proportion relative to need Meat, dairy products, and many soybean products High Biological Value Incomplete protein: lacking or low in one or more of the essential amino acids Most plant based proteins Low Biological Value Complete and Incomplete Proteins

  22. Complimentary Proteins • Two or more food proteins whose amino acid assortments complement each other in such a way that the essential amino acids limited in or missing from each are supplied by the others.

  23. V. Recommended Protein Intakes • Covers the need to replace protein-containing tissue that people lose and wear out daily

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