Protein

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Protein

• Chapter 7

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Learning Outcomes

• Describe how amino acids form proteins
• Define essential and nonessential amino acids and
  explain why adequate amounts of each of the
  essential amino acids are required for protein
  synthesis
• Distinguish between high quality and low quality
  proteins and list sources of each
• Describe how 2 low quality proteins can be
  complementary to each other to provide the
  required amounts of essential amino acids

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Learning Outcomes

• Explain the methods used to measure the protein
  quality of foods, including assessment of
  biological value
• List the factors that influence protein needs.
  Calculate the RDA for protein for a healthy adult
  with a given body weight
• Explain positive nitrogen balance, negative
  nitrogen balance and nitrogen equilibrium and
  list conditions under which they may occur

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Learning Outcomes

• Describe how protein is digested and absorbed in
  the body
• List the primary functions of protein in the body
• Describe how protein-energy malnutrition can
  eventually lead to disease in the body
• Develop a vegetarian diet plan that meets the
  bodys protein needs

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What makes proteins different from carbohydrates
and lipids?

• What elements are proteins composed of?
• What is different about their chemical structure?
• How much energy is in protein?
• What types of foods are high in protein?

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Protein in select foods
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Structure of Protein

• Contains hydrogen, oxygen, carbon and nitrogen
• Comprised of amino acids
• Nitrogen group (amine)
• Acid group (carboxyl group)
• Hydrogen
• Side chain (R-portion)
• Determines protein name

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Amino ACid
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Amino Acids

• Nonessential amino acids
• Body can produce
• Conditionally essential amino acids
• Essential during infancy, disease or trauma
• Essential amino acids
• Must be taken in via food

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Essential vs. non-essential
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Synthesis of Non Essential Amino Acids

• Transamination
• Transfer of an amine group from an amino acid to
  a carbon skeleton to form a new amino acid
• Deamination
• Amino acid losing an amine group
• Amine Group is incorporated into urea in the
  liver
• Excreted in urine

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Complete and Incomplete Proteins

• Complete Proteins
• Adequate amounts of all 9 of the essential amino
  acids
• Animal proteins-exception gelatin
• Incomplete Proteins
• Inadequate amounts of the essential amino acids
• Plant proteins-exception soy
• Complementary Proteins
• Combining plant proteins to compensate for
  limiting amino acids

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Synthesis of Protein

• Amino acids are linked by peptide bonds to form
  proteins
• Synthesis of protein determined by gene expression

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Synthesis of Proteins (Gene Expression)

• DNA unwinds
• DNA sequence is TRANSCRIBED (copied) into a
  complementary mRNA strand in nucleus
• DNA stays, but mRNA travels to the cytosol
• In the cytosol the ribosomes read the mRNA and
  TRANSLATE the message to make a specific amino
  acid
• The amino acids bond to form a protein

http//www.youtube.com/watch?v983lhh20rGY
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Transcritption
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Translation up close
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Translation up close
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Sequencing gone wrong

• Sickle cell anemia

• Sickle cell

• The amino acid valine replaces glutamic acid in
  the DNA sequence in ½ the polypeptide chains of
  hemoglobin
• This changes the shape of the protein (hemoglobin)

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Sequencing gone wrong MTHFR CgtT (ala to val)
mutation

• Thymine is in place of the more common cytosine
  in the MTHFR gene
• This results in an amino acid change, instead of
  alanine there is a valine
• This changes the structure of the enzyme, so
  those with the mutation have a less active enzyme

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Synthesis of Protein

• Protein Organization
• Primary Structure
• Sequential order of amino acids determine shape
• Secondary Structure
• Tertiary Structure
• Determines function
• Quaternary Structure

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Structure
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Denaturation and Adaptation

• Denaturation of Protein
• Altering proteins 3D structure
• Acid, alkaline, heat, enzymes and agitation
• Adaptation of Protein Synthesis
• Constant state of breakdown, rebuilding and
  repair
• Protein turnover

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Denaturation
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Sources of Protein

• Diet and recycling of body protein
• North America-70 supplied by meat, poultry,
  fish, milk and milk products, legumes and nuts
• Worldwide-35 of protein comes from animal
• How to incorporate more plant protein?

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Plant Protein
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Evaluation of Food Protein Quality

• Biological Value (BV)
• Measures how efficiently the absorbed food
  protein in converted into body tissue proteins
• If a food has an adequate amount of all 9
  essential amino acids it should be efficiently
  incorporated
• To determine the BV, nitrogen retention of the
  body is compared to the N in the food protein.
• The more N retained, the more closely the food
  protein matched the aa profile of a body protein
• Egg whites have a BV of 100

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Evaluation of Food Protein Quality

• Protein Efficiency Ratio (PER)
• Compares amount of wt gain by a growing lab rat
  vs consuming equal amount of a reference protein.
• Measures how well the protein is incorporated
  into the animal
• The PER is closely aligned with the BV

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Evaluation of Food Protein Quality

• Chemical Score
• Amount of essential amino acid/g compared to
  ideal amount based on reference protein
• Ideal is usually egg protein
• Range is from 0.0-1.0

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Evaluation of Food Protein Quality

• Protein Digestibility Corrected Amino Acid Score
  (PDCAAS)
• Chemical score x digestibility
• Most widely used

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Recommended Intakes of Protein

• Nitrogen balance studies
• Equilibrium
• Protein intake equals protein losses
• Who?
• Positive Nitrogen Balance
• Protein intake exceeds protein losses
• Who?
• Negative Nitrogen Balance
• Protein losses exceed protein intake
• Who?

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Protein RDA

• Adults
• .8 g/kg healthy body weight
• Recovery states
• .8 2 g/kg body weight
• Endurance or strength athletes
• .8 1.7 g/kg body weight
• More than this has no additional benefits!

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Protein Digestion and Absorption

• Cooking denatures protein
• Stomach
• Hydrochloric acid denatures
• Pepsin begins enzymatic digestion
• Gastrin controls the release of pepsin
• Small intestine
• CCK released which stimulates release of
  proteases
• Amino acids absorbed into the portal vein

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Protein Metabolism
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Requires Energy (active absorption)
Any remaining peptides are broken down into aa in
absorptive cell
Smallest unit gets absorbed (except in infants up
to 4-5 months-able to absorb some small proteins)
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Functions of Proteins

• Producing Vital Body Structures
• Maintaining Fluid Balance
• Edema
• Contributing to Acid Base Balance (positively
  charge H pumps in cell membranes)
• Buffers
• Forming Hormones, Enzymes and Neurotransmitters

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Fluid Balance

• Protein stays in the capillaries and helps draw
  water back into the vein from the interstitial
  tissue
• If protein intake is too low, too much fluid
  stays in interstitial tissue- edema.

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Functions of Proteins

• Transporting Nutrients
• Hormones (insulin) and nuerotransmitters (
  serotonin made from tryptophan)
• Forming Glucose
• Gluconeogenesis (when?)
• Muscle wasting is cachexia (when?)
• Providing Energy
• 4 kcal/gm

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Functions of Proteins

• Immune Function
• Innate or non specific immunity
• Acquired or specific immunity
• Anergy- immune incompetence
• Benefits of breastfeeding

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Health Concerns

• Protein- Energy Malnutrition (PEM)
• Marasmus
• Minimal amounts of energy, protein and other
  nutrients
• Kwashiorker
• Minimal amounts of protein and moderate energy
  deficit

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Food protein allergies

• When certain foods trigger an immune response
• WBC stimulate antibodies to cause the symptoms
  associated with an allergic reaction
• Eight foods account for 90 of allergies
  (peanuts, tree nuts (walnuts), milk, eggs, fish,
  shellfish, soy, and wheat)

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Special Considerations Renal diets

• Kidney role in protein metabolism
• Early stages of renal disease low protein
• If dialysis high protein, low phosphorus
• Renal disease has high risk of CVD and type 2
  diabetes

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Special Considerations Protein Supplements
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Special Considerations Protein bars
Protein Blend (Soy Protein Isolate, Whey Protein
Isolate, Calcium Caseinate), Glucose Syrup,
Chocolatey Coating (Sugar, Fractionated Palm
Kernel Oil, Cocoa, Whey, Nonfat Milk, Soy
Lecithin, Natural Vanilla Flavor), Glycerin,
Maltitol Syrup, Cookie Bits (Rice Flour, Sugar,
Canola Oil, Alkalized Cocoa, Rice Starch, Baking
Soda, Salt), Natural Flavor, Almond Butter, High
Oleic Canola Oil, Soy Lecithin, Peanut Flour,
MINERALS Calcium Phosphate, Magnesium Oxide,
Zinc Gluconate, Iron (Ferrous Fumarate), Copper
Gluconate, Chromium Aspartate, VITAMINS Vitamin
C (Ascorbic Acid), Vitamin E Acetate, Vitamin B3
(Niacinamide), Pantothenic Acid (Calcium
Pantothenate), Vitamin B6, Vitamin B2, Vitamin B1
(Thiamin Mononitrate), Folic Acid, Biotin,
Vitamin B12. CONTAINS ALMOND, MILK, PEANUT AND
SOY INGREDIENTS. MADE ON EQUIPMENT THAT ALSO
PROCESSES WHEAT.
Kcal 300 DV
Total Fat 6g 9 
Sat fat 3.5g 18 
Trans Fat 0g  
Cholesterol 0mg 0 

Sodium 170mg 7 
Total Carb 38g 13 
Dietary Fiber 1g 4 
Sugars 18g  
Protein 23g 46 
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Special Considerations Weight loss

• High Protein diets
• VLCD
• Protein Sparing Modified Fast
• Weight Loss Surgery

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Vegetarian Diets

• Types of Vegetarians
• Vegan, Lacto-ovo-vegetarians and
  Lacto-vegetarians
• Nutrient Concerns
• Protein (BV value)
• No dairy (Calcium, D, riboflavin)
• No meat (zinc, B12)
• Special Concerns for Infants and Children

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Food Plan for Vegetarians
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Non- meat sources of protein
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Vegetarian Diets

• BF Coffee w/cream and sugar and donut
• Lunch Bagel w/cream cheese, banana, diet Coke
• Snack Cereal w/berries and skim milk
• Dinner Pasta with tomato and cheese sauce,
  garlic bread, water
• Dessert Small dish of frozen yogurt