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 > error  sickle cell disease > 6 th amino acid valine is substituted for glutamine > RBC collapses, cannot carry oxygen  illness  even 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 Villi  portal vein  liver 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 Proteins  amino acids Amino acids  transported 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 spaces  EDEMA

EDEMA

ACID-BASE BALANCE Normal blood pH = 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 full  coma 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 injured  Fibrin 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 = 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 = 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

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

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 KwashiorkorLow Protein diet Normal Protein but high needs, high losses IV, Clear Liquid, Stress, Trauma, Burns MarasmusLow Kcal Low Protein Starved with chronic disease (Cancer, Malabsorption) CombinedInadequate 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 gm/dl Prealbumin – WNL mg/dl Total protein – WNL gm/dl Adipose tissue Circumferences Skin-fold measurements

NITROGEN BALANCE POSITIVE BALANCE More of the nutrient is absorbed than lost Growing children Pregnant women Adults recovering from disease EQUILIBRIUMIntake 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 = – [13 + 3] gm N/day (catabolism)

ANABOLISM Protein intake = 75 gms/day UUN = 6 gm/day then: 75/6.25 = – [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 PROTEINBVCHEMICALNPU EGGS100 MILK93 75 RICE8667 BEEF75 80 FISH75 83 CORN72 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 level  decrease in cardiovascular disease Decreased Bone Loss  less calcium loss

VEGETARIAN CONCERNS Biological value Nutrient density Complementary amino acids – Mutual supplementation or Complementation High fiber  poor 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