chapter5
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ProteinProtein
Chapter 5
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What Are Proteins?What Are Proteins?
• Complex molecules• Amino acids
• Peptide bonds– Condensation reaction
• Nitrogen
• Classification• Number of amino acids
– Oligopeptides and polypeptides
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What Are Proteins?What Are Proteins?
• Amino acids• Three common parts
• Central carbon bonded to a hydrogen
• Amino group (-NH2)
• Carboxylic acid (-COOH)
• R-group
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The Main Components of an The Main Components of an Amino AcidAmino Acid
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What Are Proteins?What Are Proteins?
• Amino acids• Classification
• Essential – 9 amino acids
• Nonessential – 11 amino acids
• Conditionally essential – 6 amino acids
• Transamination• α-keto acid
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Essential, Nonessential, & Essential, Nonessential, & Conditionally Essential Amino AcidsConditionally Essential Amino Acids
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Are All Food Proteins Equal?Are All Food Proteins Equal?
• Categorization of food proteins• Complete protein sources
• Sources
• Incomplete protein sources • Limiting amino acids
• Protein complementation
• Protein quality • High-quality vs. low-quality protein sources
• GMOs
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How Are Proteins Made?How Are Proteins Made?
• Step 1: Cell signaling initiates protein synthesis• Up-regulation• Down-regulation
• Step 2: Transcription transfers genetic info• Chromosomes and genes• Messenger ribonucleic acid (mRNA)
• Step 3: Translation produces new peptide• Ribosomes • Transfer ribonucleic acid (tRNA)
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The Steps of Protein SynthesisThe Steps of Protein Synthesis
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How Do Proteins Get Their How Do Proteins Get Their Shapes?Shapes?
• Protein structure• Primary structure
• Number and sequence of amino acids
• Critical to function of protein
• Sickle cell anemia
• Secondary structure• α-helix
• β-folded sheets
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The Primary Structure of a The Primary Structure of a ProteinProtein
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The Secondary Structure of a The Secondary Structure of a ProteinProtein
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How Do Proteins Get Their How Do Proteins Get Their Shapes?Shapes?
• Protein structure• Tertiary structure
• Folding due to R-group interactions
• Quaternary structure • Two or more peptide chains come together• Prosthetic groups
• Denaturation • Denaturating agents • FDA and EPA recommendations
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The Quaternary Structure & The Quaternary Structure & Prosthetic Groups of HemoglobinProsthetic Groups of Hemoglobin
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Genetics, Epigenetics, Nutrition, Genetics, Epigenetics, Nutrition, and Nutrigenomics and Nutrigenomics
• Genetic alterations• Mutations
• Chance genetic modification
• Polymorphism
• Health and disease risks
• Epigenetics • Connection between genes & physiology
• Chronic degenerative disease risk
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Genetics, Epigenetics, Nutrition, Genetics, Epigenetics, Nutrition, and Nutrigenomicsand Nutrigenomics
• Nutrigenomics• How nutrition and genetics interact to influence
health
• Human Genome Project
• Future for personalized nutrition
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How Are Dietary Proteins How Are Dietary Proteins Digested, Absorbed, & Circulated?Digested, Absorbed, & Circulated?
• Chemical digestion begins in the stomach• Gastrin
• HCl– Disrupts secondary, tertiary, and quaternary
structures– Converts pepsinogen to pepsin
• Pepsin– Breaks bonds between amino acids
• Mucus and other substances
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How Are Dietary Proteins How Are Dietary Proteins Digested, Absorbed, & Circulated?Digested, Absorbed, & Circulated?
• Protein digestion continued in small intestine• In lumen and enterocytes
• Secretin and CCK• Pancreas releases bicarbonate
• Pancrease releases proenzymes – Trypsin– Chymotrypsin– Elastase– Carboxypeptidase
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Overview of Protein DigestionOverview of Protein Digestion
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How Are Dietary Proteins How Are Dietary Proteins Digested, Absorbed, & Circulated?Digested, Absorbed, & Circulated?
• Absorption occurs in small intestine• Transported from lumen into brush border cells
• Passive and active transport mechanisms
• Circulation• Circulated to liver via the hepatic portal system
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How Are Dietary Proteins How Are Dietary Proteins Digested, Absorbed, & Circulated?Digested, Absorbed, & Circulated?
• Food intolerance
• Food allergy• Common allergens
• Signs and symptoms
• Anaphylaxis
• Best prevention is avoidance
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What Are the Major Functions of What Are the Major Functions of Proteins & Amino Acids in the Body?Proteins & Amino Acids in the Body?
• Provide structure• Important during periods of growth and
development
• Enzymes • Catalysts
• Speed up chemical reactions
• Facilitate movement • Skeletal muscle• Actin and myosin
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What Are the Major Functions of What Are the Major Functions of Proteins & Amino Acids in the Body?Proteins & Amino Acids in the Body?
• Transport proteins• Protein deficiency
• Communication• Hormones
• Cell-signaling process
• Immune system• Antibodies
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What Are the Major Functions of What Are the Major Functions of Proteins & Amino Acids in the Body?Proteins & Amino Acids in the Body?
• Fluid balance• Intracellular vs. extracellular space
• Intravascular vs. interstitial fluid
• Edema
• Regulate pH
• Glucose synthesis and ATP production• Gluconeogenesis
• Other purposes
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Regulation of Fluid Balance by Regulation of Fluid Balance by AlbuminAlbumin
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Protein and Energy MetabolismProtein and Energy Metabolism
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Protein Turnover, Urea Protein Turnover, Urea Excretion, and Nitrogen BalanceExcretion, and Nitrogen Balance
• Protein turnover • Proteolysis
• Labile amino acid pool
• Regulated by hormones
• Urea excretion • Deamination
• Ammonia (NH3)
– Liver converts to urea
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Urea Synthesis and ExcretionUrea Synthesis and Excretion
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Protein Turnover, Urea Protein Turnover, Urea Excretion, and Nitrogen BalanceExcretion, and Nitrogen Balance
• Nitrogen balance• When protein loss equals protein intake
• Measure of overall protein status
• Negative nitrogen balance
• Positive nitrogen balance
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How Much Protein Do You How Much Protein Do You Need?Need?
• Reasons for protein consumption• Essential amino acids• Needed additional nitrogen
• DRIs for amino acids• RDAs• No ULs
• DRIs for proteins• RDAs• Life stages with higher protein recommendations
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The RDAs for the Essential The RDAs for the Essential Amino Acids in AdultsAmino Acids in Adults
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How Much Protein Do You How Much Protein Do You Need?Need?
• Protein needs of athletes• Debated among experts
• DRI committee• International Society of Sport Nutrition• American College of Sports Medicine
• Supplements
• Other recommendations• AMDRs• USDAs dietary source recommendations
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Vegetarian Diets: Healthier Than Vegetarian Diets: Healthier Than Other Dietary Patterns?Other Dietary Patterns?
• Various forms of vegetarianism• Lacto-ovo-vegetarian
• Lactovegetarians
• Vegans • Deficiency risks
• Key to a healthy vegetarian diet• Wide variety of foods in moderation
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What Are the Consequences of What Are the Consequences of Protein Deficiency?Protein Deficiency?
• Children are especially affected
• Protein-energy malnutrition (PEM)• Micronutrient deficiencies
• Types• Marasmus
– Severe, chronic, overall malnutrition– Adults and children
• Kwashiorkor – Edema and ascites
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Protein Excess: Is There Cause Protein Excess: Is There Cause for Concern?for Concern?
• Not causally associated with adverse health outcomes
• High protein intakes often accompanied by high intakes of fat, saturated fat, and cholesterol
• Intake of red meat or processed meats • Increased cancer risk
• Recommendations
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Nutrition MattersNutrition Matters
Food Safety
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Foodborne illness• Disease caused by ingesting unsafe food
• Causes• Infectious agents
• Noninfectious agents
• Strains of microorganisms• Serotypes – genetic strains or types
• Incubation period
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Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,
Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection
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Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,
Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection
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Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,
Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Preformed toxins • Serious and rapid reactions
• Staphylococcus aureus • Toxin is not easily destroyed by cooking
• Common foods
• MRSA• “Community acquired”
• MRSA-infected foods
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Preformed toxins• Clostridium botulinum
• Food sources
• High cooking temperatures destroy the toxin
• Disease of botulism
• Aspergillus• Aflatoxin
• Food sources
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Enteric toxins • Result in diarrhea in one to five days
• Noroviruses • Symptoms
• Cannot be treated with antibiotics
• Some serotypes of E. coli
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Enterohemorrhagic • Invasion of intestinal cells
• Signs and symptoms
• Salmonella • Food sources
• Incubation period
• E. coli O157:H7 and E. coli O104:H4• Incubation period
• Food sources
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Parasites• Protozoa
• Cysts
• Giardia intestinalis – Symptoms
• Worms • Trichinella
• Anisakis simplex
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What Causes Foodborne What Causes Foodborne Illness?Illness?
• Prions • Altered proteins
• Secondary structure is disrupted
• Resilient
• Mad Cow disease
• Creutzfelt-Jakob disease • Variant Creutzfeldt-Jakob disease
• WHO recommendations
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How Can Noninfectious Substances How Can Noninfectious Substances Cause Foodborne Illness?Cause Foodborne Illness?
• Algae toxins• Shellfish poisoning
• Marine toxins• Red tide
– Brevetoxins
• Pesticides• Herbicides• Antibiotics• Hormones
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How Can Noninfectious Substances How Can Noninfectious Substances Cause Foodborne Illness?Cause Foodborne Illness?
• Food allergies and sensitivities• Monodosium glutamate (MSG)
• Sulfites
• Food proteins
• New concerns• Acrylamide
• Melamine
• Bisphenol A (BPA)
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How Do Food Manufacturers How Do Food Manufacturers Prevent Contamination?Prevent Contamination?
• Food-handling techniques• Food production, preservation, and packaging
• Hazard Analysis Critical Control Points (HACCP)
• Salting, smoking, drying, and fermentation• Heat treatment• Pasteurization • Cold treatment• Irradiation
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Guidelines for Cooking, Serving, & Guidelines for Cooking, Serving, & Reheating Foods to Prevent Reheating Foods to Prevent
Foodborne IllnessFoodborne Illness
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What Steps Can You Take to What Steps Can You Take to Reduce Foodborne Illness?Reduce Foodborne Illness?
• Check consumer advisory bulletins• FightBac!
• Clean• Hands, surfaces, and cooking utensils
• Wash• Fruits and vegetables
• Separate foods• Cook foods to proper temperature • Chill
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What About Avoiding Foodborne What About Avoiding Foodborne Illness While Traveling or Camping?Illness While Traveling or Camping?
• Drink only purified or treated water• Bottle water
• Avoid ice
• Avoid or carefully wash fresh fruits & veggies
• Avoid beef and beef products• Areas with variant Creutzfelt-Jakob disease
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What Are Some Emerging What Are Some Emerging Issues of Food Biosecurity?Issues of Food Biosecurity?
• Food biosecurity • Prevention of terrorist attacks on food supply
• Bioterrorism Act
• Changes in food production and distribution • Origin of food on label