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UB NTR 108 - Nutrition 108 Exam 2

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Cristal LeeNutrition Exam 2: pg 56-113Module V. ProteinA. Structure:1. Proteins are long chains of subunits seen as a 3-dimensional structure2. Basic Unit of a protein=amino acid *20 different amino acidsa. Amino Acids1. Structure:a. Amine group- always has Nitrogenb. Carbon skeleton- central carbon with hydrogen (backbone)- acid group- The r-group (side chain) *makes each amino acid different -differentiates one amino acid from another -determines the structure and function of the amino acid2. Peptide Bonda) Links together two amino acidsb) Needs to be broken during digestion b. Dipeptides: two amino acids c. Polypeptides: Many amino acids 3. The structure an function of proteins are determined by their amino acid sequence-There are 20 diff. amino acids, therefore lots of different structures can be producedin the body. 4. Each different protein has a unique amino acid sequence which is encoded in the cellular DNA a. DNA transcribed into RNA- RNA acts a messenger; carries genetic info from DNA to site of protein synthesis b. RNA translated into protein- Puts the amino acids in correct orderB. Protein is an essential nutrient1. Essential amino acids (EAA)- Cannot be made by the body- Must be included in diet to maintain optimal protein status- Provide a source of nitrogen for other componds- Can be used as an energy source2. Non-essential amino acids (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 sourceC. Functions of Proteins1. Structural: muscle2. Growth: infancy, pregnancy3. Maintenance and repair of body tissues4. Energy- 4kcals/g- Secondary role-if we used it all for energy, we would not have any for the other important roles5. Hormone production a. Insulin, glucagon, secretin6. Blood proteins a. Regulation of fluid balance (edema) b. Maintenance of acid-base balance c. Involved in blood clotting d. Delivery of oxygen to tissues e. Transport proteins1. Albumin2. Lipoproteins7. Enzymes a. Speed up and control chemical reactions1. Digestion2. Absorption3. Metabolism8. Immune Functiona. AntibodiesD. Protein Digestion-stomach, acid of the stomach *Goal of digestion is to get to the single amino acid 1. Denaturation results in a loss of protein function and exposure of peptide bonds for digestion.2. During digestion, protein in food is broken down into the individual amino acids3. The body uses this pool of amino acids to make new tissues and to maintain existing tissues.a. Mouth1. Grinding and mixing of food**b. Stomach1. Protein with 3D structure denatured with acid2. Acid breaks some bonds3. Pepsin (an enzyme) breaks more bonds c. Pancreas1. Enzymes secreted into small intestine for protein digestiond. Small Intestine1. Proteins and Polypeptides digested by pancreatic enzymes2. Small peptides broken into dipeptides and amino acids by intestinalenzymesE. Protein Absorption1. In the adult, essentially all protein must be absorbed as amino acids or dipeptides2. Small Intestinea. Taken up into the electrocyte (cells lining the GIT)1. amino acids or dipeptides are absorbed2. Secondary active transport3. carried with sodium (like glucose)4. Use different transporter based on R groupa. Can affect protein quantity if very unbalancedb. Competitive inhibition-taking high amts of one amino acids can block absorption of another amino acid***Capillaries -> portal vein -> liverb. Released as amino acids into capillariesc. Capillaries go to portal veinPart of enterohepatic circulationd. Portal Vein goes to liver3. Livera. Amino acids can be taken up before the rest of body gets a chanceb. Regulates level of amino acids in bloodF. Amino Acid Metabolism*1. Transamination=Transfer-Transfer of an amine group from an amino acid to the carbon skeleton to form a new (different) amino acid a. Used for1. formation of nonessential amino acids b. Vitamin B6 is needed-In the absence of vitamin B6, all amino acids would be essential**2. Deamination=Removala. Used for1. Excretion of amine2. energy production from amino acidb. Vitamin B6 is also needed**3. Nitrogen excretiona. Loss of nitrogen in1. Feces (as protein)2. Skin, hair, nails (as protein)3. Urine (as urea)= by liver and kidneysb. Excess nitrogen (amine group)1. Synthesized into urea in the liver2. Urea is transported to the kidney and excreted in the urineG. Protein Requirement1. Based on balance=intake minus output a. Intake (into the body and used)1. Amount of proteina. Better usage when lower (to a point)b. Poorer usage when high (used for energy)2. Protein Quality (rating the protein)a. Digestibility affects qualityb. Amino acid content determines protein quality-Amino acid score-Based on the amount of the EAA (essential amino acid) in the lowest proportionc. Terms associated with protein quality- Complete protein (all 9 essential amino acids)-all EAA in the optimal rations (meat, eggs, dairy)- Incomplete proteins-missing or having a low amt of one or more EAAs (grains, beans, and vegetables)- Complementary proteins-Two proteins that have a high amt of the EAA that is low in the other-Combination of the proteins leads to a high quality protein intake (beans and rice)d. Animal proteins versus plant proteinsQuality Animal PlantHigh (ideal) Egg QuinoaVery good Milk, meat SoyGood LegumesFair GrainsPoor Gelatinb. Output1. Feces (depends mainly on digestibility) of digestion, mostly2. Urine (depends on intake and quality)3. Insensible Losses (not very controllable)- Skin, Nails, Hair, Sweat, and otherc. Need1. Maintenance a. Sedentary (need 0.8g protein x kg body weight)b. Active lifestyle (need extra 10-15grams a day)2. Pregnancy3. Lactation4. Growtha. Infancy (highest protein needs per kg)b. Childhoodc. Adolescence5. Exercisea. Endurance/cardiovascular (use more protein for fuel)b. Weight training (protein needed to build muscle tissue)6. Diseasea. Injury-(Burn patients-very high protein needs)b. Illness- (Aids or cancer patients may have increased protein needs)2. Protein requirement (RDA)a. Adult**0.8g protein x kg body weight/per day (e.g. 170 pound male. 170/2.2=77kg 77kg*0.8g/kg=62g protein/day)b. Based on1. Average loss of nitrogen per day2. How much protein is required to replace nitrogen losses3. Protein quality4. Adjustment for population variability (generous recommendations)H. Vegetarianism***1. Typesa. Vegan 1. No animal products (no meat, poultry,


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