Transcript PROTEINS
PROTEINS PROTEINS Organic compounds Acid and amino group * nitrogen**** * side group AMINO ACID STRUCTURE AMINO ACID EXAMPLES AMINO ACIDS Basic building blocks of protein 20 amino acids 9 essential or indispensable-2 totally essential deprived of essential AA body breaks down own proteins 11 non-essential or dispensable body can make if proper amount of C, H, O, N Conditionally essential Linked by peptide bonds Dipeptide, tripeptide, polypeptide CONDENSATION AMINO ACIDS Squencing: > specific order-exquisite and precise order > genetically determined > errorsickle cell disease > 6th amino acid valine is substituted for glutamine > RBC collapses, cannot carry oxygenillnesseven death AMINO ACIDS Denaturation Change may be irreversible Heat, alcohol, acids, salts of heavy metals disrupt normal chain Excess acidity or alkalinity damages body’s proteins DENATURATION DIGESTION/ABSORPTION Mouth breaks up food Stomach HCl activates pepsinogen to pepsin Pepsin breaks down large polypeptides Beginning of protein digestion DIGESTION – SMALL INTESTINE Intestinal proteases and pancreatic proteases break down polypeptides oligopeptides, tripeptides, dipeptides Intestinal peptidases convert peptides to amino acids Intestinal villi amino acids portal vein to liver Liver – monitors protein synthesis and frees amino acids to circulation CATABOLISM – no storage Bloodstream TRANSPORT OF AMINO ACIDS Transport by diffusion Villiportal veinliver Liver monitors: 1. Protein synthesis 2. Free amino acids to circulation 3. Catabolism Proteins are NOT stored- constant synthesis and catabolism Represents ~ 15-20% of REE FUNCTIONS OF PROTEIN Growth, maintenance Enzymes Hormones Antibodies Fluid and electrolyte balance Acid-base balance Transportation Blood clotting Visual pigments Energy GROWTH, MAINTENANCE Growth – manufacture cells Repair – collagen Replacement Protein turnover – synthesis and degradation ENZYMES - CATALYSTS ANTIBODIES Antigens are invaders (bacterium, toxins, virus, allergens) Body detects antigens works to make antibodies Antibody made with amino acids – pattern stored in DNA memory Adequate protein aids immune system in making antibodies FLUID BALANCE Proteinsamino acids Amino acidstransported to cell –crosses cell wall Inside cell build proteins Large proteins do not cross over cell wall Proteins made inside cell hold water inside Proteins in bloodstream will draw fluid back into blood FLUID BALANCE Blood pressure from pumping action of heart forces fluid into tissue spaces Proteins in bloodstream draw water back into bloodstream as pressure declines Without sufficient protein fluid remains in tissue spacesEDEMA EDEMA ACID-BASE BALANCE Normal blood pH = 7.35-7.45 Protein act as BUFFERS Acidosis - acid (Low pH) = H+ ions Proteins accept H+ ions Alkalosis - base ( pH) = H+ ions Proteins release H+ ions Proteins can (+) or (-) H+ ions to maintain balance If proteins not available or fullcoma or death TRANSPORT PROTEINS Specific for compound or group of related compounds Cell membranes-maintain equilibrium * in and out of cells * move into membrane but shuttle side to side Carrier 1. Vitamins and minerals Fe – captured by protein (ferritin) in intestinal wall ferritin holds in bone marrow or other tissue until body needs Fe Protein (transferrin) carries Fe through bloodstream 2. Oxygen transport and use protein (hemoglobin) combines with Fe to carry O2 in fluids or myoglobin (protein) in muscle cells 3. Lipids- lipoproteins BLOOD CLOTTING Tissue injuredFibrin made Stringy protein fibers to plug leak Also need Vit K and Calcium BLOOD CLOTTING - FIBRIN PROTEIN FOR ENERGY Low priority use of protein Energy needs must be meet Increased need for water ENERGY Deamination Nitrogen stripped off ammonia liver carbon skeleton + CO2 urea gluconeogenesis excreted by kidneys energy OR stored as fat PROTEIN EXCESS NO storage – store as fat May overload kidneys May contribute to excess calorie intake May contribute to calcium excretion Use of animal proteins increase fat and cholesterol intake Fat and CHO are protein sparing PROTEIN RECOMMENDATIONS As % of total energy needs = 10-15% of calories Grams/kilogram of body weight/day = 0.8-1.0 grams of protein/kilogram RDA = 0.8 grams/kg of body weight Protein needs affected by: illness, stress, age Low protein diet fatty liver, low skeletal mass DO ATHLETES NEED MORE PROTEIN???? Casual aerobics 3 times/week 1 gram/kg more than enough Strength building: to make new muscle Depends on LBM 1 gram/kg of body weight Endurance (marathon, triathlon)-Muscle repair – muscle supplies 10-15% of energy during 1 hour run 2 grams/kg body weight Begin training = 1-1.2 gms/kg INGESTING LARGE QUANTITIES OF PROTEIN DOES NOT CAUSE MUSCLE TO INCREASE IN SIZE HEALTH EFFECTS OF PROTEIN PEM – Protein-energy malnutrition PCM – Protein-calorie malnutrition Most widespread form of malnutrition today Affects adults, but especially children Acute – thin for height Chronic – short for age KWASHIORKOR MARASMUS KWASHIORKOR AND MARASMUS KWASHIORKOR KWASHIORKOR Adequate calories with low protein intake Adipose tissue preserved Skeletal muscle preserved or decreased Relatively normal weight Serum proteins decreased Edema Growth failure Fatty liver Apathy Misery Hair changes – pluckability, color strength, texture MARASMUS MARASMUS Low Kcals and low protein intake Low adipose tissue Low skeletal mass Significant weight loss Serum proteins relatively normal No edema Ketosis Immune system compromised Decreased metabolism Decreased body heat Slows brain development-retardation Growth retardation Looks old and sick NUTRITION THERAPY Fluid balance- electrolytes Low fat milk – protein carriers Add fat Protein repletion MALNUTRITION IN HOSPITALIZED PATIENTS Kwashiorkor Low Protein diet IV, Clear Liquid, Normal Protein but Stress, Trauma, high needs, high Burns losses Marasmus Low Kcal Low Protein Starved with chronic disease (Cancer, Malabsorption) Combined Inadequate diet with high protein losses and stress Starved with stress EVALUATE FOR PCM Skeletal muscle Mid-arm muscle circumference Creatinine–height index: 24 hour urine collection – compare to standards Serum proteins Albumin – WNL 3.5-5.0 gm/dl Prealbumin – WNL 20-50 mg/dl Total protein – WNL 6.0-8.4 gm/dl Adipose tissue Circumferences Skin-fold measurements NITROGEN BALANCE POSITIVE BALANCE More of the nutrient Growing children is absorbed than Pregnant women lost Adults recovering from disease EQUILIBRIUM Intake equals losses Healthy adults NEGATIVE BALANCE Losses from body exceed intake Adult with disease (cancer) Fasting/starvation NITROGEN BALANCE CALCULATIONS N balance = protein intake/6.25 – [output (UUN) + 3] Normal UUN = 6-17 gm/day Protein intake = 60 gm/day UUN = 13 gm/day then: 60/6.25 = 9.6 9.6 – [13 + 3] 9.6 - 16 -6.4 gm N/day (catabolism) ANABOLISM Protein intake = 75 gms/day UUN = 6 gm/day then: 75/6.25 = 12 12 – [6 + 3] 12 – 9 +3 HIGHEST QUALITY PROTEIN? PROTEIN QUALITY Chemical scoring Biological value (BV) Net protein utilization (NPU) Protein efficiency ratio Reference protein = egg = 100 (FAO of U.N.) PROTEIN QUALITY PROTEIN BV CHEMICAL NPU EGGS 100 100 100 MILK 93 93 75 86 67 RICE BEEF 75 75 80 FISH 75 75 83 CORN 72 72 56 PROTEIN QUALITY LIMITING AMINO ACID Essential amino acid – not enough for protein synthesis COMPLETE PROTEINS All essential amino acids in amounts required by humans COMPLEMENTARY PROTEINS Combining foods with limiting amino acids to make complete protein DIGESTIBILITY COMPLETE/INCOMPLETE PROTEIN SOURCES COMPLEMENTATION VEGETARIAN DIETS VEGANS – avoids all animal foods SEMI – VEGETARIAN – no red meat Lacto-ovo Vegetarian – Avoids meat but uses eggs and dairy products Lacto-Vegetarian – Avoids meat and eggs but uses dairy products Vegetarians may need more total protein in diet: 45 grams of high quality protein vs 65 grams of lower quality protein BENEFITS TO VEGETARIANISM Lower Calories IBW, Lower BP Higher fiber diet decreased risk of Cancer increased digestive function Lower Blood Cholesterol leveldecrease in cardiovascular disease Decreased Bone Lossless calcium loss VEGETARIAN CONCERNS Biological value Nutrient density Complementary amino acids – Mutual supplementation or Complementation High fiberpoor nutrient absorption Risk of low iron, vit. D intake Risk of inadequate zinc Risk of inadequate amino acids Vit B12 deficiency Lacto-ovo may be high fat diet Children at risk for nutritional deficiencies ALLERGIC REACTIONS