Protein NTR 108 Protein Topics Protein structure Types of protein Functions of protein Protein digestion absorption and metabolism Vitamin B6 Protein requirements Vegetarian diets Protein deficiency Supplements Objectives 1 Describe the structure of proteins 2 List the functions of proteins 3 Discuss how proteins are digested absorbed and transported by our body 4 Describe the dangers of inadequate protein intake 5 Describe the types of vegetarian diets along with their benefits and potential concerns Protein PART 1 PROTEIN STRUCTURE Protein Structure Proteins are long chains of subunits seen as a 3 dimensional structure Basic unit of a protein is an amino acid Amino acids Structure Central carbon with hydrogen backbone Amine group Always has a Nitrogen Acid group R group side chain Differentiates one amino acid from another Determines the structure Determines function of the amino acid Peptide Bond Links together two amino acids Needs to be broken during digestion Module V Protein Protein Structure Dipeptides 2 Amino acids Polypeptides Many amino acids acid sequence produced in the body The structure and function of proteins are determined by their amino There are 20 different amino acids therefore lots of different structures can be Each different protein has a unique amino acid sequence which is encoded in the cellular DNA DNA is copied onto mRNA RNA translated into protein Puts the amino acids in correct order mRNA acts as a messenger carries genetic information from DNA to site of protein synthesis Protein Protein Structure Protein PART 2 AMINO ACIDS AND PROTEIN FUNCTIONS Protein An Essential Nutrient Protein is an essential nutrient Essential amino acids EAA 9 EAA Cannot be made by the body Must be included in the diet to maintain optimal protein status Provide a source of nitrogen for other compounds Can be used as an energy source Non essential amino acids NEAA 11 NEAA Amino acids that the body is able to make from other substances in the diet Provide a source of nitrogen for other compounds Can be used as an energy source Protein Functions Structural Muscle Growth Infancy pregnancy Maintenance and repair of body tissues Energy 4 kcals gram Secondary role if we used it all for energy we would not have any for the other important roles Hormone production Insulin Glucagon CCK Secretin Protein Functions Blood proteins Regulation of fluid balance Prevents edema swelling of the tissues Maintenance of acid base balance Involved in blood clotting Fibrin Delivery of oxygen to tissues Transport proteins Albumin Lipoproteins Enzymes reactions Immune function Antibodies Speed up and control chemical Protein PART 3 PROTEIN DIGESTION ABSORPTION AND METABOLISM Protein Digestion 1 Denaturation results in a loss of protein function and exposure of peptide bonds for digestion 2 Protein in food is broken down into the individual amino acids 3 Body uses pool of amino acids to make new tissues and to maintain existing tissues Locations of Digestion 1 Mouth Grinding and mixing of food 2 Stomach Protein with 3D structure denatured exposes bonds with acid Acid breaks some bonds Pepsin an enzyme breaks more bonds Enzymes secreted into small intestine for protein digestion 3 Pancreas 4 Small intestine Proteases enzymes from the pancreas and small intestine digest polypeptides Amino acids and di tripeptides absorbed into enterocyte where peptidases digest them into single amino acids Protein Absorption 1 Protein absorbed into the enterocytes cells lining the small intestine as amino acids dipeptides or tripeptides a Secondary active transport Carried with sodium b Use different transporter based on R group Can affect protein quality if very unbalanced Competitive inhibition Taking high amounts of one amino acids can block absorption of another amino acid c Released as amino acids into capillaries bloodstream d Capillaries go to portal vein Part of enterohepatic circulation circulation between small intestine and liver e Portal vein goes to liver 2 Liver a Amino Acids can be taken up before the rest of body gets a chance b Regulates level of amino acids in blood Amino Acid Metabolism 1 Transamination Transfer of an amine group from an amino acid to the carbon skeleton to form a new different amino acid Used for Formation of nonessential amino acids Vitamin B6 is needed In the absence of Vitamin B6 all amino acids would be essential Amino Acid Metabolism 2 Deamination Removal of the amine group from an Energy production from amino acid or gluconeogenesis for some amino acid Used for amino acids Nitrogen is excreted Vitamin B6 is also needed 3 Nitrogen excretion Excess nitrogen from amine group is synthesized into urea in the liver Urea is transported to the kidney and excreted in the urine Nitrogen also lost through Feces as protein Skin Hair Nails as protein Vitamin B6 Definition Classification Water soluble vitamin Functions Amino acid metabolism transamination to Heme synthesis hemoglobin in red blood make NEAA cells Deficiency signs symptoms Anemia Vitamin B6 Good Dietary Sources Meat Fish Poultry Eggs Dairy products Peanut butter Potatoes Green vegetables Bananas Whole grain cereals Supplements Used to treat PMS carpal tunnel syndrome Excess supplements toxicity Nerve damage and skin lesions Protein Digestion and Amino Acid Metabolism Protein PART 4 PROTEIN REQUIREMENTS Protein Requirements Protein requirement is based on the goal of nitrogen balance where nitrogen intake equals nitrogen output 1 Protein Intake into the body and used Amount of protein Better usage when lower to a point Poorer usage when high used for energy Protein quality rating the protein Digestibility affects quality Animal proteins and soy are most digestible 90 of amino acids absorbed Legumes 70 80 grains and vegetables 60 90 Amino acid content determines protein quality Based on the amount of the EAA essential amino acid in the lowest proportion Limiting amino acid amino acid missing or in lowest supply Complete high quality protein contains all EAA in the optimal ratios Incomplete low quality protein missing or low in one or more EAAs Meat eggs dairy fish Grains beans and vegetables Complementary proteins Two incomplete proteins that when combined provide sufficient amounts of all EAA make a complete protein Beans and Rice Protein Requirements 2 Output Feces depends mainly on digestibility Urine Insensible Losses Skin Nails Hair Sweat and other Protein Requirements 3 Need 0 8 g protein per kg body weight per day