CHAPTER 7 PROTEIN Overview of Protein Named from Greek protos to come first 17 of body weight Body is made up of thousands of proteins found in Muscle Connective tissue Organs DNA Hgb Antibodies Enzymes Regulates and maintains body FCN Structure of Protein Made up of C H O and nitrogen Compromised of amino acids Building blocks of proteins AA arranged in chains 20 AA in humans Structure of Amino Acids Basic or generic structure Carbon skeleton 1 C 1 H and side chain R Amino group contains nitrogen Acid group carboxyl Amino Acids Nonessential amino acids 11 Body can produce Not needed in the diet Essential amino acids 9 Must be taken in through food Not synthesized by the body Conditionally Essential amino acids Essential during infancy disease or trauma Synthesis of Nonessential Amino Acids Transamination Transfer of amino group from one AA to a carbon skeleton to form a new AA Deamination The AA losing the amine group without transferring it to a carbon skeleton Amine group is incorporated into urea in the liver Excreted in urine Complete and Incomplete Proteins Complete proteins high biological value BV Adequate amounts of all essential AA Animal proteins except gelatin Similar to our protein so easily absorbed Incomplete proteins low biological value Inadequate amounts of one or more essential AA Plant proteins except soybeans and quinoa Complementary proteins Combining incomplete proteins to compensate for the limiting amino acid Limiting Amino Acid Essential AA that is missing or in the smallest supply Slows or halts protein synthesis Protein Synthesis Proteins are long chains of amino acids Amino acids are joined to each other by peptide bonds amino group acid carboxyl group Di tri oligo polypeptide The structure of each protein is dictated by the DNA of a gene Determined via gene expression Transcription mRNA copies the genetic information from DNA Translation The genetic information in RNA is converted CHAPTER 7 PROTEIN into the amino acids sequence of protein Genetic Disease Some genetic disease can result in protein abnormalities Ex sickle cell anemia Protein Organization Primary Structure sequence of amino acids Determines shape of protein Secondary Structure How AA sequence folds locally Forms spiral shape Tertiary Structure unique 3D folding of the secondary structure elements Determines function Quaternary Structure 2 or more separate polypeptide chains interact to form a large new protein Activates FCN Ex Hgb 4 polypeptides Denaturation of Proteins Alteration of tertiary 3D protein structure Benefits Cons digestion safety can alter normal FCN Protein Turnover and repair Allows adaptions in response to diet exercise injury illness etc Ingested proteins are degraded to provide building blocks for new proteins Sources of Protein Diet and recycling of body protein Worldwide 35 of protein comes from North American 70 supplied by meat poultry fish milk and milk products legumes and nuts animal sources Incorporate more plant than animals because more cholesterol and fiber Evaluation of Food Protein Quality Protein quality is typically defined as a protein s capacity to provide essential amino acids to an individual Biological Value BV Egg white is highest BV 100 All N absorbed is retained and used in body protein Protein Efficiency Ratio PER Equation gain in body mass protein intake Chemical Score mg limited AA test Pro mg limiting AA ideal Pro Protein Digestibility Corrected Amino Acid Score PDCAAS Chemical score x digestibility Preferred best method Recommended Intakes of Protein Positive Nitrogen Balance N protein intake N protein loss Protein Needs AMDR IOM 10 35 kcals Adult RDA 0 8 g kg healthy body weight Weight in lbs 2 2 weight in kg Recovery states 0 8 2 g kg body weight Endurance or strength athletes Protein synthesis response to Negative Nitrogen Balance changing conditions N protein intake N protein loss Constant state of breakdown rebulding Equilibrium N protein intake N protein loss CHAPTER 7 PROTEIN 0 8 1 7 g kg body weight Excess protein from diet or supplemental sources cannot be stored as protein It is used as fuel glucose or stored as fat Protein Digestion Cooking denatures proteins Heat and acids Protein digestion begins in the stomach Gastrin hormone secreted by stomach to stimulated gastric juice production HCL denatures proteins activates pepsin Pepsin enzyme that breaks down long polypeptide chains into shorter chains Small intestine Chyme triggers release of secretin CCK Both stimulate release of pancreatic proteases trypsin chymotrypsin carboxypeptidase Polypeptides short peptides amino acids Protein Absorption Short peptides amino acids in the lumen of SI are absorbed into absorptive cells Via active transport polypeptidase breaks down short peptides in AA Polypeptides short peptides AAs AAs travel via the portal vein To what Used for protein synthesis NRG conversion to CHO or fat or released into the bloodstream for other cells Functions of Proteins Maintaining fluid balance Producing vital body structures Contributing to acid base balance buffers Forming hormones enzymes neurotransmitters Contributing to immune function Transporting nutrients Carrier proteins Forming glucose gluconeogenesis Providing energy 4 kcals g Health Concerns Related to Protein Intake Protein Energy Malnutrition Kwashiorkor protein deficit with moderate energy deficit Marasmus protein energy deficit High Protein Diets Food and Nutrition Board rec s No more than 35 total kcals from protein Excess protein does notprovide health benefits Increases health and disease risk Damage kidneys excrete excess nitrogen as urea overburden kidney capacity to excrete water is needed to dilute urea increases risk of dehydration If high animal protein likely low plant foods Low in phytochemicals fiber vitamins High in sat fat cholesterol Increases risk for CVD and certain cancers increases urinary Ca loss Leads to bone loss osteoporosis kidney stones If excessive AA supplementation can cause AA imbalances and toxicity methionine cysteine histidine Food Protein Allergies CHAPTER 7 PROTEIN Allergens food protein cause immune response creating an allergic reaction 8 food account for 90 of all food allergies Peanuts tree nuts eggs fish shellfish soy wheat and milk Food allergies are not Food intolerances Vegetarian Diets Types of Vegetarians Vegans Lacto vegetarians Lacto ovo vegetarians fruitarians pescatarians flexitarian raw vegan etc Nutrient Concerns B12 Ca iron zinc vitamin D