ProteinProtein

Chapter 5

What Are Proteins?What Are Proteins?

• Complex molecules• Amino acids

• Peptide bonds– Condensation reaction

• Nitrogen

• Classification• Number of amino acids

– Oligopeptides and polypeptides

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

The Main Components of an The Main Components of an Amino AcidAmino Acid

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

Essential, Nonessential, & Essential, Nonessential, & Conditionally Essential Amino AcidsConditionally Essential Amino Acids

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

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)

The Steps of Protein SynthesisThe Steps of Protein Synthesis

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

The Primary Structure of a The Primary Structure of a ProteinProtein

The Secondary Structure of a The Secondary Structure of a ProteinProtein

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

The Quaternary Structure & The Quaternary Structure & Prosthetic Groups of HemoglobinProsthetic Groups of Hemoglobin

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

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

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

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

Overview of Protein DigestionOverview of Protein Digestion

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

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

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

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

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

Regulation of Fluid Balance by Regulation of Fluid Balance by AlbuminAlbumin

Protein and Energy MetabolismProtein and Energy Metabolism

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

Urea Synthesis and ExcretionUrea Synthesis and Excretion

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

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

The RDAs for the Essential The RDAs for the Essential Amino Acids in AdultsAmino Acids in Adults

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

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

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

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

Nutrition MattersNutrition Matters

Food Safety

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

Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,

Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection

Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,

Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection

Infectious Agents of Foodborne Illness, Infectious Agents of Foodborne Illness,

Food Sources, & Symptoms of InfectionFood Sources, & Symptoms of Infection

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

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

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

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

What Causes Foodborne What Causes Foodborne Illness?Illness?

• Parasites• Protozoa

• Cysts

• Giardia intestinalis – Symptoms

• Worms • Trichinella

• Anisakis simplex

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

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

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)

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

Guidelines for Cooking, Serving, & Guidelines for Cooking, Serving, & Reheating Foods to Prevent Reheating Foods to Prevent

Foodborne IllnessFoodborne Illness

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

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

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