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