PROTEINS
PROTEINS
Organic compounds
Acid and amino group * nitrogen**** * side group
AMINO ACID STRUCTURE
AMINO ACID EXAMPLES
AMINO ACIDSBasic 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 ACIDSSquencing:
> 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 diffusionVilliportal veinliverLiver 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 PROTEINGrowth, maintenanceEnzymesHormonesAntibodiesFluid and electrolyte balanceAcid-base balanceTransportationBlood clottingVisual pigmentsEnergy
GROWTH, MAINTENANCE
Growth – manufacture cells
Repair – collagen
Replacement
Protein turnover – synthesis and degradation
ENZYMES - CATALYSTS
ANTIBODIESAntigens 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 BALANCENormal blood pH = 7.35-7.45Protein act as BUFFERSAcidosis - acid (Low pH) = H+ ions
Proteins accept H+ ionsAlkalosis - base ( pH) = H+ ions
Proteins release H+ ionsProteins can (+) or (-) H+ ions to maintain balanceIf proteins not available or fullcoma or death
TRANSPORT PROTEINSSpecific 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
DeaminationNitrogen 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 caloriesGrams/kilogram of body weight/day = 0.8-1.0 grams of protein/kilogramRDA = 0.8 grams/kg of body weightProtein needs affected by:
illness, stress, ageLow 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 weightBegin training = 1-1.2 gms/kgINGESTING 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 intakeAdipose tissue preservedSkeletal muscle preserved or decreasedRelatively normal weightSerum proteins decreasedEdemaGrowth failureFatty liverApathyMiseryHair changes – pluckability, color strength, texture
MARASMUS
MARASMUSLow Kcals and low protein intakeLow adipose tissueLow skeletal massSignificant weight lossSerum proteins relatively normalNo edemaKetosisImmune system compromisedDecreased metabolismDecreased body heatSlows brain development-retardationGrowth retardationLooks 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
Normal Protein but high needs, high losses
IV, Clear Liquid,
Stress, Trauma, Burns
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 PCMSkeletal muscle
Mid-arm muscle circumference Creatinine–height index: 24 hour urine
collection – compare to standardsSerum 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 BALANCEPOSITIVE BALANCE
More of the nutrient is absorbed than lost
Growing children
Pregnant women
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/dayProtein 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
RICE 86 67
BEEF 75 75 80
FISH 75 75 83
CORN 72 72 56
PROTEIN QUALITYLIMITING 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 foodsSEMI – VEGETARIAN – no red meatLacto-ovo Vegetarian – Avoids meat but uses eggs and dairy productsLacto-Vegetarian – Avoids meat and eggs but uses dairy productsVegetarians 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