Transcript Chapter
Protein Introduction to Protein Protein’s Primary Jobs Structure • Muscles, tendons, & ligaments • Skin & hair • Blood & tissues Working proteins • • • • Enzymes Antibodies Transport vehicles Hormones Protein’s Secondary Job Energy = 4 kcal/g Amino Acids: The Building Blocks of Protein ©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark used herein under license. Body uses 20 amino acids to make proteins Consist of: Central Carbon Amino group (NH2) Acid group (COOH) Side Chain (R-group) R ©2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning ™ is a trademark used herein under license. Examples of amino acids Classification of Amino Acids Essential Nonessential Body can’t make, must come from diet Body can make Conditionally essential Becomes essential due to inadequate availability or disorder of metabolism Ex: PKU makes tyrosine essential Classification of Amino Acids Primary Structure of Proteins # & sequence of amino acids Amino acids bound in peptide bonds = polypeptide Determines protein’s physical & chemical properties and its function Sickle Cell Anemia Disease caused by single error in amino acid sequence of hemoglobin Red blood cells rigid, sticky, shaped like a sickle Signs Anemia, pain in chest, abdomen & joints, swollen hands & feet, frequent infections, stunted growth, vision problems Secondary Structure of Protein Polypeptide strand forms coils and folds because of chemical attractions between individual amino acids Structure of Proteins Tertiary Structure folds and loops of coils Quaternary Structure The union of several polypeptides in a protein Ex:hemoglobin Protein Synthesis Protein Breakdown & Digestion Denaturation = disruption of shape Heat --- cooking (ex: frying egg) Acids/bases --- chemicals in digestive system Salts of heavy metals --toxins (ex: mercury) Goal of digestion is to liberate amino acids so body can reconfigure them Protein Digestion Stomach HCl and enzyme gastrin break up protein strands Small intestine Numerous enzymes break down polypeptide strands into smaller diand tripeptides. Amino acids absorbed through intestinal wall Food Allergies When larger polypetides are absorbed Body’s immune system responds Side effects Mild rashes Swelling of throat & airways Sources & Quality of Amino Acids & Proteins in Diet Protein Sources: Meat, Poultry, Fish Eggs Dairy products Legumes, soy Nuts Complete vs incomplete Quality Score Protein Complementation Combining foods with incomplete proteins to provide adequate amounts of all essential amino acids Examples: Rice & beans Corn & beans Photo 6.2 Functions of Amino Acids & Protein in Body Protein and Energy RDA for Protein 0.8 g protein/kg body weight Increases during Infancy Pregnancy Lactation Do athletes need more? Do vegetarians need more? Protein in Sports Nutrition Increased protein or AA intake alone does not trigger muscle growth Research: Exercise is required stimulus! Studies based on nitrogen balance; methods controversial Novel training increases protein needs As fitness improves, protein needs return to baseline Accepted ranges: Endurance athletes: 1.2-1.4 g/kg Strength athletes: 1.6-1.7 g/kg Vegetarian Diets Types Lactovegetarian Lacto-ovo-vegetarian Include milk Include milk & eggs Vegan No animal products whatsoever Additional Guidelines for Protein Intake Natl. Acad Sci Inst. of Med. recs: 10-35% of energy Assumes kcal intake is sufficient DGAs & MyPyramid Fat-free or low-fat milk 2-7 oz. lean meat Legumes - 2-3 cups Problem with excess?