proteins enzymes, hormones, and body building lecture 4 february 2, 2015 dr. ponnusamy
TRANSCRIPT
PROTEINS
Enzymes, Hormones, and Body Building
Lecture 4February 2, 2015Dr. Ponnusamy
Department of Food Science
Lecture 4: February 2, 2015
Instructors’ Contact
• Dr. Loredana Quadro Food Science Department, Room 419 Office hours: Thursday 2:30-4:30 pm (no office hours
Feb 5, 2015)
• Dr. Chitra Ponnusamy [email protected]
• Dr. Mary Wasserman [email protected]
Department of Food Science
Lecture 4: February 2, 2015
Six Classes of Nutrients
1. Carbohydrate- macronutrient; yields energy
2. Fats- macronutrient; yields energy
3. Proteins- macronutrient; yields energy
4. Vitamins - micronutrient
5. Minerals - micronutrient
6. Water- macronutrient; no energy
Department of Food Science
Lecture 4: February 2, 2015
The word “protein”
Derived from the Greek word proteios, which means “of the first rank”
Coined by Jon BerzeliusSwedish chemist
discovered that an extract of potatoes is more effective than concentrated sulfuric acid in promoting the breakdown of starch
Department of Food Science
Lecture 4: February 2, 2015
Sources of Protein in the Diet
• In the US, about two-thirds of dietary protein comes from meat, poultry, seafood, eggs and dairy products.
• Most of the world relies on plant proteins from grains, legumes and vegetables.
• As a country’s economy improves, the proportion of animal foods in the diet tends to increase.
• Protein deficiency is rare in the United States.
Department of Food Science
Lecture 4: February 2, 2015
Functions of Body Proteins
• No living tissue can be built without protein
• Protein is part of every living cell
• Proteins account for ~ 20% of body weight
• Proteins come in many forms
• Proteins perform many vital functions
Body proteins are not static; they undergo constant breakdown and are resynthesized. This process is called protein turnover.
Department of Food Science
Lecture 4: February 2, 2015
• Protein is very critical in the regulation of human metabolism. It is used to form muscle, connective tissue,
blood clotting factors, blood transport proteins, lipoproteins, visual pigments, and the protein matrix inside the bones.
Lipoproteins help transport lipids in the body.
Department of Food Science
Lecture 4: February 2, 2015
• Protein is also used to maintain the body fluid balance by producing albumin and globulin. Without
sufficient protein in the blood stream, edema would quickly develop.
Department of Food Science
Lecture 4: February 2, 2015
• Dietary protein also contributes to the acid-base balance by producing buffers that help regulate the
amount of free hydrogen ions in the blood. This accepting or donating of hydrogen ions helps to keep the blood pH slightly alkaline (pH 7.35 to 7.45).
Department of Food Science
Lecture 4: February 2, 2015
• The immune system is also composed of proteins. Antibodies are proteins. Without enough
dietary protein, the immune system will lack the cells needed to function properly, thus energy or the lack of an immune response can appear.
Department of Food Science
Lecture 4: February 2, 2015
• ENERGY SPARING ACTION OF PROTEINS:
Dietary protein can also be used as an energy source . If a diet does not contain enough carbohydrate to supply needed glucose, proteins can be used to synthesize glucose.
Department of Food Science
Lecture 4: February 2, 2015
PROTEINS THUS FUNCTION AS:
Enzymes – over 2000 – necessary for digestion and catalase reactions
Hormones – regulate metabolic reactions• Examples: insulin and adrenaline
Immune functions• antibodies (immunoglobulins)
Department of Food Science
Lecture 4: February 2, 2015
• Transport and Storage proteins hemoglobin, myoglobin, lipoproteins
• Structural proteins for Mechanical Support keratin, collagen, elastin Examples of body structures include skin, hair, nails,
membranes, muscles, teeth, bones, organs, ligaments and tendons.
• Contractile -Muscle proteins myosin, actin, tubulin
Protein, along with calcium is necessary to maintain bone mass and prevent fractures!
Department of Food Science
Lecture 4: February 2, 2015
Protein As Energy
• In the absence of adequate energy, the body will sacrifice protein to provide energy
• The amine group will be degraded (DEAMINATION), incorporated by the liver into urea, and sent to the kidneys for excretion in urine (urea: the principal nitrogen excretion product of metabolism)
Energy from proteins: 4 Calories per gram
Department of Food Science
Lecture 4: February 2, 2015
Proteins are made of Amino Acids (building block of proteins)Amino acids differentiate proteins: Each amino acid has an
amino group, an acid group, a hydrogen atom, and a side
group (R-group)
R-CH-NH2-COOH
R-group differentiates the amino acids from each other
Nitrogen differentiates proteins from carbs and fat
Department of Food Science
Lecture 4: February 2, 2015
Protein
20 Amino Acids + 3D Structures
> 100,000 different proteins
Different protein structures are formed from amino acids owing to:variations in number, proportion and order of amino acids
Department of Food Science
Lecture 4: February 2, 2015
Amino Acids 20 total amino acids 9 are essential Remaining 11 can be
synthesized by body (non-essential)
ESSENTIAL AMINO ACIDS MUST BE SUPPLIED BY THE DIET
NONESSENTIAL AMINO ACIDS ARE THE ONES THE BODY CAN CREATE
O OCCNH
H
H H+
--
SIDEGROUP
Department of Food Science
Lecture 4: February 2, 2015
9 ESSENTIAL AMINO ACIDS
1. HISTIDINE 6.PHENYLALANINE
2. ISOLEUCINE 7. THREONINE
3. LEUCINE 8. TRYPTOPHAN
4. LYSINE 9. VALINE
5. METHIONINE
Department of Food Science
Lecture 4: February 2, 2015
11 NONESSENTIAL AMINO ACIDS
• Human body has the capability of synthesizing the 11 nonessential amino acids.
• When these amino acids are in short supply transamination or the transfer of an amine group (nitrogen group) from an amino acid to a carbon skeleton to form a new amino acid takes place.
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Protein Structure
• Peptide bonds are chemical bonds that link amino acids together.
• Peptide bonds are formed between the acid group of one amino acid and the nitrogen group of the next amino acid.
• Dipeptide bonds are formed between two amino acids.
• Polypeptides are formed between many amino acids.
• A protein is made of one or more polypeptide chains folded into a three-dimensional shape.
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Protein Structure
Department of Food Science
Lecture 4: February 2, 2015
PEPTIDE BONDS
• AMINO ACID CHAINS ARE LINKED TOGETHER BY PEPTIDE BOND
• 2 AA= DIPEPTIDE
• 3 AA= TRIPEPTIDE
• MULTIPLE AMINO ACIDS= POLYPEPTIDE
• FOODS CONTAIN POLYPEPTIDES
Department of Food Science
Lecture 4: February 2, 2015
Insulin : an example of multiple amino acids linked into a protein chain
http://www.chem.uwec.edu/Chem406/Webpages/Ying/overview.htm
Porcine Pro-Insulin:● 3 chains● 74 amino acids
Human and Bovine Insulin:● 2 chains● 51 amino acids
Department of Food Science
Lecture 4: February 2, 2015
Recommended Protein IntakesRecommended protein intakes can be stated by two
methods. As a percentage of total calories:
• Protein should provide 10-35% of total calories As an absolute number (grams per day).
• A healthy adult should consume 0.8 gram per kilogram of desirable body weight per day
• Calculation:
Weight: 150 pounds = 68 Kg (150/2.2)
Grams protein: 68 x 0.8 = 54g protein
Department of Food Science
Lecture 4: February 2, 2015
Increased protein needs
• Growth
• Illnesses
• Injuries
• Pregnancy
• Lactation
Nitrogen Balance
Department of Food Science
Lecture 4: February 2, 2015
Nitrogen Balance
• The term "nitrogen balance" refers to the amount of nitrogen the body excretes, as opposed to the amount of nitrogen the body takes in.
• All of the macronutrients — protein, carbohydrate, and fat — are made up of carbon, hydrogen, and oxygen molecules.
Department of Food Science
Lecture 4: February 2, 2015
• Protein alone also contains an additional nitrogen molecule. When the body digests protein, these nitrogen molecules are generally released into the blood.
• Measuring body nitrogen levels can be the most accurate way to determine whether the body is receiving adequate, inadequate, or excess protein.
Department of Food Science
Lecture 4: February 2, 2015
Nitrogen Balance
• a determination made about the body's ability to meet its protein needs which is reached by comparing the amount of nitrogen taken in with the amount discharged via urine, hair, skin, or perspiration.
Department of Food Science
Lecture 4: February 2, 2015
Negative nitrogen balance
• A body condition in which nitrogen output exceeds nitrogen intake
• Reflects on the body's need to draw on its own stores of protein for energy
• may be caused by dietary imbalances, illness, infection, anxiety, or stress.
Department of Food Science
Lecture 4: February 2, 2015
Positive Nitrogen Balance
• a body condition in which nitrogen intake exceeds nitrogen output;
• a normal state for children, pregnant women, or individuals recovering from illness or surgery
• These individuals require extra protein in order to build tissue.
• Excess protein can also help athletes and body builders recover faster from workouts.
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Nitrogen Balance
Department of Food Science
Lecture 4: February 2, 2015
Protein Source Consumption
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
• Animal products provide sources of protein, B vitamins and minerals such as iron, zinc and calcium.
• However, animal products are low in fiber and can be high in fat.
• Plant sources of protein are also a good source of B vitamins, iron, zinc, fiber and calcium, but in less absorbable forms.
Department of Food Science
Lecture 4: February 2, 2015
Protein Quality: based on essential amino acids
• Complete Protein: Needed for growth
• Proteins from animal foods are 90-99% absorbed Contain all the essential amino acids in the
right proportion• Milk, Meat, Eggs
Soy is the only plant source of complete protein.
Department of Food Science
Lecture 4: February 2, 2015
• Partially Complete Protein
Lacking or low in one or more of the essential amino acids
Plant proteins are 70-90% absorbed
• Example: Gliadin protein of wheat
Department of Food Science
Lecture 4: February 2, 2015
• Limiting Amino Acid- the missing essential amino acid Essential amino acid in shortest supply
(relative to the body’s need) in a food protein
limits the body’s ability to make its own proteins
.
Department of Food Science
Lecture 4: February 2, 2015
HIGH QUALITY PROTEINS
• ANIMAL FOODS - CONTAIN ALL ESSENTIAL AMINO ACIDS; HENCE TERMED HIGH QUALITY PROTEINS EGG WHITE PROTEIN- BIOLOGICAL VALUE 1.0;
REFERENCE PROTEIN CASEIN- MILK PROTEIN- A COMPLETE PROTEIN
• PLANT FOODS – TEND TO MISS ONE OR MORE ESSENTIAL AMINO ACIDS
Except: SOY Protein- Complete with 9 essential amino acids
Department of Food Science
Lecture 4: February 2, 2015
Protein Quality of Foods
Complementary proteins
two or more food proteins whose amino acid assortments complement each other in such a way that the essential amino acids limited in or missing from each are supplied by the others.
Department of Food Science
Lecture 4: February 2, 2015
AA Limiting Proteins
FOOD LIMITING AMINO ACID
Rice lysine
Corn lysine
Wheat lysine
Legume (beans) methionine
Mutual complementation: complementary proteins supply all the essential amino acids; an important consideration for vegetarians
Vegetarian diets include animal products, like dairy.
Department of Food Science
Lecture 4: February 2, 2015
Protein Quality – PB&J example
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Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Meeting Protein Needs with a Vegan Diet
Grains and legumes are considered good sources of proteins.
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Protein Shape Determines Function
• The final shape of a protein determines its function.
• Connective tissue proteins and collagen are elongated.
• Hemoglobin has a spherical shape.
• If the shape of a protein is altered, its function may be disrupted.
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
If Protein Shape is Altered, Function May Be Altered
Department of Food Science
Lecture 4: February 2, 2015
DENATURATION OF PROTEINS
PROTEINS ARE ALWAYS COILED
UNDERGO UNCOILING; IRREVERSIBLE
THIS IS CALLED DENATURATION
FUNCTIONAL ABILITY CHANGES
EXAMPLE- EGG PROTEIN
Department of Food Science
Lecture 4: February 2, 2015
DENATURATION
• CAUSES HEAT EXPOSURE TO
ACID
• EFFECTS PROTEIN’S 3-D
STRUCTURE ALTERED
BROKEN DOWN INTO POLYPEPTIDES
PREPARATION FOR DIGESTION
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Proteins that May Harm Certain Individuals: Phenylketonuria
• PKU is an inherited condition attributed to a defective gene.
• Aspartame, a sugar substitute, contains phenylalanine.
Tyrosine is considered a conditionally essential amino acid
Food Proteins and Health
Department of Food Science
Lecture 4: February 2, 2015
Protein and Health: Deficiency
Marasmus From the Greek ‘to waste away’ Lack of calories and protein
• Starvation Sufferers weigh only HALF as
much as normal
Kwashiorkor Caused by an acute lack of
protein Bloated look associated with
starvation Wasted muscles
Marasmus Kwashiorkor
http://cnhs.gmu.edu/hsci530nurs534/04-MacronutrientMalnutrition.doc
Department of Food Science
Lecture 4: February 2, 2015
Protein and Health: Excess
The problems of protein excess can be found in developed countries Possible to overload the liver and kidneys;
potential risk of kidney stones Can promote calcium excretion Excess protein can be converted to energy
and stored as body fat No apparent benefit to consuming too much
protein when caloric intake is adequate
Department of Food Science
Lecture 4: February 2, 2015
Allergies
• Food allergens = proteins that are not broken down by the digestive tract which then cross the GI lining to enter the blood stream
• 8 foods cause 90% of all allergic reactions egg fish milk peanuts shellfish soy tree nuts wheat
http://www.foodallergy.org/index.html
The immune system is involved
Department of Food Science
Lecture 4: February 2, 2015
• Additional Slides
Department of Food Science
Lecture 4: February 2, 2015
Copyright 2010, John Wiley & Sons, Inc.
Amino Acids
Department of Food Science
Lecture 4: February 2, 2015
Soy
Heart Health ClaimClaim requirement (need to say on label):
1. 25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of [name of food] supplies __ grams of soy protein OR
2. Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease. One serving of [name of food] provides __ grams of soy protein
Department of Food Science
Lecture 4: February 2, 2015
According to the US Food and Drug Administration:
Soy protein products can be good substitutes for animal products because, unlike some other beans, soy offers a 'complete' protein profile. ... Soy protein products can replace animal-based foods—which also have complete proteins but tend to contain more fat, especially saturated fat—without requiring major adjustments elsewhere in the diet. •Ref: Henkel, John (May–June 2000). "Soy:Health Claims for Soy Protein, Question About Other Components". FDA Consumer (Food and Drug Administration) 34 (3): 18–20.PMID 11521249
•Negative of soy consumption in large quantities is the hormonal effects.
Department of Food Science
Lecture 4: February 2, 2015
Whey
• Milk Protein
• High in sulfur containing amino acids antioxidant anticarcinogen immune stimulating
• High concentrations of the branched chain amino acids - muscles
http://www.wheyoflife.org/faq.cfm#1
Department of Food Science
Lecture 4: February 2, 2015
Reported Whey Benefits
• Cardiovascular benefits (antihypertensive and hypocholesteremic)
• Anticarcinogenic effects
• Antibacterial and antiviral properties
• Antioxidant actions
• Immune system stimulation
• Improved bone formation/reduced bone loss
• Increased mineral absorption
• Reduction of tooth enamel demineralization and plaque formation
• Appetite suppression
• Rebuilding of muscle tissue
Department of Food Science
Lecture 4: February 2, 2015
Protein & Athletes, Sports
• Intake of dietary protein 1.2 - 1.6 grams of protein per kilogram of body weight can almost always be obtained in the normal diet
• Special mixtures of amino acids stimulating muscle growth NO solid evidence
• Amino acids and CHO metabolism No hard evidence that this occurs or has bearing on sport
performance
BOTTOM LINE: Exercise hard, eat right (a varied diet), rest
http://www.gssiweb.com/reflib/refs/258/rt42.cfm?pid=38
Department of Food Science
Lecture 4: February 2, 2015
Function of Food Proteins
1. Water Binding
gelatin, non-fat dry milk solids
2. Browning- non enzymatic
Maillard - chemical reaction
3. Structure
gluten for bread, egg white meringue
4. Sweetening
aspartame
5. Fat Substitute
microsized egg protein
Department of Food Science
Lecture 4: February 2, 2015
Protein Functions in Foods
Beverages………………………….. Viscosity
Soups, sauces……………………... Viscosity, emulsification
Dough, baked goods……….……… Matrix, gelation, browning
Dairy…………………………………. Fat retention, Emulsification
Egg substitutes……………………… Foaming, Gelation
Meat products………………………. Absorption, Cohesion
Food coating…………….…………… Cohesion
Confectionary…………..……………. Dispersibility, emulsification