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Chapter 6: Proteins & Amino Acids
Copyright 2012 John Wiley & Sons, Inc. All rights reserved.
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Proteins & Amino Acids
The word protein comes from the Greek
proteios meaning of primary importance
Protein are essential to every cellular funtion
Catalyze chemical reactions
Fundamental components of skeletal and
muscular tissue
Vital to inmune response
2012 John Wiley & Sons, Inc. All rights reserved.
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Student learning outcomes: At the end
of this chapter, you should be able to:
Describe the role of proteins and amino acids
in health and disease
Plan a diet to meet protein recommendations
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THINK about thisthen share within
a PAIRthen SHARE with the class
What do you know about proteins and amino
acids?
What are benefits of eating plant foods over
animal foods?
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Sources of protein
Animal: meat, eggs, dairy products High in saturated fat and cholesterol; provide B
vitamins and some absorbable minerals (iron, zinc,calcium) low in fiber
Plant: grains, nuts, legumes Low in saturated fat and cholesterol; high in fiber,
phytochemicals, and unsaturated fat Legumes: starchy plant seeds producing bean pods,
including peas, peanuts, beans, soybeans, lentils,chickpeas
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Sources of protein
Animal products are high on protein, iron, zinc, and calcium but also
add saturated fat and cholesterol to the diet
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Sources of protein
Plant source of
protein are rich in
fiber, phytochemical,
and monosaturated
and polysaturated
fats
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Amino acids: building blocks of proteins Carbon, hydrogen, amino group (contains nitrogen),
acid group, and side chain
20 different side chains make 20 different amino
acids
Amino acids
The generalstructure
of an amino acid
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Building blocks
Match the building blocks with the nutrient:
____ complex carbohydrates a) amino acids
____ triglycerides b) fatty acids and glycerol
____ proteins c) polysaccharides
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Amino acids link to form proteins
Aminoacids linked by
peptide bonds are
called peptides. When
two amino acids are
linked, they form a
dipeptide; three form atripeptide. Many amino
acids bonded together
constitute a
polypeptide.
Polypeptide chains may
contain hundreds of
amino acids.
The order and chemical
properties of the amino
acids in a polypeptidechain determine how
the polypeptide folds
and, hence, the three-
dimensional shape of
the protein.
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Amino acids link to form proteins
We obtain amino acids from eating plant andanimal foods.
Our bodies reassemble the amino acidbuilding blocks into our body proteins.
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Essential vs. non-essential amino acids
Essential/indespensible: Cannot be made in
the body so essential to eat them
If one is missing, body proteins are broken down to
make new proteins
Non-essential/despensible: Body can make
them from other proteins so not essential to
eat them
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Essential vs. non-essential amino acids
Twenty amino acids are
commonly found in
proteins. The table show
here lists them based on
whether they are essential
or nonessential and
indicates those that are
conditionally essencial
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Amino acids structure
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Amino acids structure
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Grupo I. Aminocidos apolares. Aminocidos cuyo resto R
no es polar. Esto es, no posee cargas elctricas en R al tener
en l largas cadenas hidrocarbonadas. Estos aminocidos, si
estn en gran abundancia en una protena, la hacen insoluble
en agua.
Grupo II Aminocidos polares no ionizables. Poseen
restos con cortas cadenas hidrocarbonadas en las que
hay funciones polares (alcohol, tiol o amida).
Contrariamente al grupo anterior si una protena los tiene
en abundancia ser soluble en agua.
Grupo III Aminocidos polarescidos. Pertenecen a este grupo
aquellos aminocidos que tienen
ms de un grupo carboxilo. En las
protenas, si el pH es bsico o
neutro, estos grupos se encuentran
cargados negativamente.
Grupo IV Aminocidos polares
bsicos. Son aquellos aminocidosque tienen otro u otros grupos
aminos. En las protenas, estos
grupos amino, si el pH es cido o
neutro, estn cargados
positivamente.
Amino acids structure
http://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva12.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva13.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva13.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva10.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva12.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva11.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva11.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva10.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva14.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva13.GIFhttp://web.educastur.princast.es/proyectos/biogeo_ov/2BCH/B1_BIOQUIMICA/t15_PROTEINAS/diapositivas/Diapositiva12.GIF -
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Relacin de los aminocidos y sus
abreviaciones correspondientes
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Essential vs. non-essential amino acids
FoodA Food B
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Essential vs. non-essential amino acids
Can you use only the amino acids
from FoodA to make this protein?
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Essential vs. non-essential amino acids
Can you use only the amino acids
from FoodA to make this protein?
The yellow triangle is anon-essential amino acid
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Essential vs. non-essential amino acids
Can you use only the amino acids
from FoodA to make this protein?
The blue square is alimiting amino acid
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Essential vs. non-essential amino acids
Can you use only the amino acids
from FoodA to make this protein?
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Essential vs. non-essential amino acids
Can you use only the amino acids
from Food B to make this protein?
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Essential vs. non-essential amino acids
Can you use only the amino acids
from FoodsA and B to make this protein?
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Essential vs. non-essential amino acids
Did you use all of the amino acids
from FoodsA and B to make this protein?
It not, what did the body do with the extras?
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Essential vs. non-essential amino acids
FoodsA and B are complementary: each
supplies some amino acids for the full set
of needed amino acids
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Essential vs. non-essential amino acids
Essential amino acids
Cannot be made
Need to be eaten
Non-essential amino acids
Can be made from others
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What a scientist sees
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Protein folding
Amino acids interact to form the 3-dimensional
structures of proteins
Structures of proteins determines their functions
If protein structure is changed, then protein function
may change
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Protein folding
The final structure of
a protein molecule
consists of one ormore folded
polypeptide chain
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Protein denaturation
Denaturation:change in a proteins three-dimensional shape
Occurs with: Heat from cooking or a fever
Low pH in the stomach or when the body becomes
acidic (for example, in diabetic ketoacidosis)
Neurodegenerative diseases such as Alzheimersdisease, mad cow disease, Parkinsons disease
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Protein denaturation
Denaturation. Alteration of a proteins three-dimensional structure
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Concept check
Which chemical element is found in protein butnot in carbohydrate or lipid?
What determines whether an amino acid mustbe consumed in the diet?
What determines the shape of a protein?
How does denaturation affect protein function?
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Protein
digestion
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Application
Insulin is a protein. Why do diabetics need to
inject insulin rather than take it orally?
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The purple amino acids are absorbed by the same
transport system as the green amino acids. If youconsume a sports drink that is supplemented withthe green amino acids what will happen to theabsorption of the purple ones.
Protein digestion
a) nothingb) the larger amount of green ones
will limit the absorption of thepurple ones
c) the small amount of the purpleones will be absorbed first
d) both will be absorbed equallybecause the body needs them
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Concept check
Where does the chemical digestion of proteinbegin?
Why might supplementing one amino acidreduce the absorption of other amino acids?
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Amino acid pool
Amino acid pool: amino acids available for
use in the body
From the diet or breakdown of body proteins
Used to make other proteins or chemicals (forexample: DNA, RNA, histamine, etc.)
Used to provide energy or make glucose or fatty
acids
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Amino acid pool
The amino acids in the amino acid pool come from _________ and ___________.
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Genes contain instructions for proteins
Each gene contains the instructions for oneRNA molecule. RNA is transcribed (re-written)from DNA.
Messenger RNA (mRNA) molecules exit thenucleus and contain instructions for the orderofamino acids in a protein. The nucleotideinstructions in DNA and RNA are translated to
the amino acid language ofproteins.
P i
h i
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Protein synthesis
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Genes contain instructions for proteins
S h i i i
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Synthesizing proteins
The instructions for making proteins are contained in the nucleus of the cell in
stretches of DNA called genes.
When a protein is synhesis begins, and the information contained in the gene
is used to make the necessary protein.
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Gene mutations
Changes in gene sequence can change thesequence of the amino acids in a protein
Changes in (amino acid) sequence can change howa protein folds and change its structure
Changes in protein structure can change proteinfunction
+ - -
i kl ll i
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sickle-cell anemia
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Gene regulation
All cells contain the same DNA. During development,
some genes are turned on and others are turned off so
cells can carry out specific functions.
For example, insulin-producing cells turn on the insulin gene
and turn off muscle contraction genes.
Chemicals can turn genes on and off.
For example, high iron turns on the ferritin gene to make more
ferritin which is needed for iron storage.
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Concept check
Building blocks of proteins are:
a) nucleotides
b) amino acids
c) DNA and RNA
d) codons
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Concept check
Amino acids are linked together:
a) During translation
b) In the nucleus
c) When DNA is made from RNA
d) During transcription
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Protein functions
Speed up chemical reactions
Structures
Some chemical signals (for example, hormones)
Transportation of substances
Movement of muscles
Immunity (for example, antibodies)
Blood clotting
Fluid balance
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Body Proteins Provide Many Functions
Proteins provide structure
The most visible example is the protein in muscles
Skin and hair are also composed largely of protein
The most abundant protein in the body is collagen; it holds cells togetherand forms the protein framework of bones and teeth
Enzyme proteins speed up metabolic reactions
Enzymes are proteins that speed up metabolic reactions but are notused up or destroyed in the process
Enzymes that function in the body are made by the body and thereforedo not need to be consumed in the diet
d i id i
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Body Proteins Provide Many Functions
Proteins transport molecules throughout our body
Transport proteins act as shuttles. In the blood they carry substancesfrom one organ to another. For example, hemoglobin, the protein thatgives red blood cells their red color, picks up oxygen in the lungs andtransports it to other organs of the body
Proteins protect us from injury and infection Skin, which is made up primarily of protein, is the first barrier against
infection and injury
Proteins help us move
Some hormones are proteins
Proteins help regulate fluid balance
Proteins help regulate acidity
Protein functions
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Protein functions
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Protein functions
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Using proteins
Amino acids from the diet are used to make
proteins and nitrogen-containing molecules
Extra amino acids cannot be stored
Extra amino acids are used for energy or
stored as fat
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Using proteins for energy
When we do not consume enough calories to
meet needs, body proteins are broken down
since amino acids are not stored
Deamination removes amino group (NH2) Produces urea which is excreted in urine
Carbon, hydrogen, and oxygen can be broken
down to produce ATP or used to make glucoseor fatty acids
Using proteins for energy
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Using proteins for energy
h k
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Concept check
Why does protein synthesis stop when the
supply of an amino acid is limited?
How does the body know in what order toassemble the amino acids when making a
protein?
When is protein used as an energy source?
P i l i i (P M)
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Protein-energy malnutrition (PEM)
Loss of fat and muscle and decreasedimmunity from long-term protein and calorie
deficiencies
Types:
Kwashiorkor: pure protein deficiency
Marasmus: overall energy deficiency
Protein energy malnutrition (PEM)
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Protein-energy malnutrition (PEM)
P i
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Protein excess
Increased urea output
Increased demands on the kidneys
Increased loss of water from the body
Possible increased loss of calcium Increased risk of kidney stones
Hi h i di
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High-protein diets
Usually:
high in animal proteins with high saturated fat
and cholesterol and low in fiber
low in grains, fruits, and vegetables
high in calories and fat
Increased risk of heart disease, cancer,
obesity, and diabetes
P i ll i
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Protein allergies
When a protein is absorbed intact, the
immune system can recognize it as an
antigen and start cellular reactions
The second time immune system detects thatsame allergen (allergy-causing antigen), there
is an allergic reaction
Major food allergens: milk, eggs, peanuts,tree nuts, fish, shellfish, soy, and wheat
P i f d l b l
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Protein on food labels
F d i i i i
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Food sensitivities
Do not involve the immune system
Trigger various symptoms after consumption
Examples:
MSG symptom complex or Chinese restaurant
syndrome
Gluten intolerance or Celiac disease
Consumption of gluten in rye, wheat or barley triggers anautoimmune reaction against villi in the small intestines
C h k
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Concept check
What are consequences of low or high protein
diets?
Ni b l
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Nitrogen balance
Nitrogen intake equals nitrogen loss
Maintaining body protein and weight
Negative nitrogen balance:
more nitrogen lost than consumed
From illness, injury, or decreased consumption
Positive nitrogen balance:
more nitrogen consumed than lost
From growth, pregnancy, or weight training
Nitrogen balance
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Nitrogen balance
P t i d d d il ll
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Protein recommended daily allowanceDuring the first year of life, growth is rapid, so a large amount
of protein is required per unit of body weight. As growth rate
slows, requirements per unit of body weight decrease butcontinue to be greater than adult requirements until age 19.
What is the RDA for a 2-year-old child who weighs 14
kilograms?
a)14 g/day
b)15.4 g/day
c)11.2 g/day
d)21 g/day
P t i d d d il ll
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Protein recommended daily allowance
0.8 g/kilogram of body weight for adults
With more weight, more protein is needed for
maintenance and repair
70 kg (154 lb) adult = 56 g of protein/day Average consumption = 70 g of protein/day
Higher needs in infants, during pregnancy
and lactation (breast feeding), after injury,
and in endurance athletes
Pregnant/lactating women: add 25 g of protein/day
C l l t
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Calculate
100 pound adult
weight in kilograms equals weight in pounds
x0.45 kg/lb
Protein RDA = 0.8 g/kilogram of body weight
How much protein does this person need?
Pr t i i t k i thl t
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Protein intake in athletes
Protein supplements
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Protein supplementsProtein and amino acid supplemens
Protein and amino acid supplements are rarely needed to meet protein needs. Nonetheless,
supplements are marketed to boost total protein intake, to add individual amino acids, and
to provide enzyme activity
Protein dietary recommendations
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Protein dietary recommendations
Acceptable Macronutrient Distribution Rangefor protein:10% to 35% of calories
Dietary Guidelines 2010 recommend that we
choose a variety of protein foods, includingseafood, lean meat and poultry, eggs, beans,
soy products, and unsalted nuts and seeds
Protein quality
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Protein quality
High-quality, or complete dietary, proteins
Contain all amino acids to meet bodys needs
More easily digested
Animal proteins and soy
Incomplete proteins
Lower in one or more essential amino acids Most plant proteins
Use complementary proteins
Complementary proteins
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Complementary proteins
Choosing healthy proteins
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g y p
Debate
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Debate
Should you switch to soy?
What should I eat?
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What should I eat?
Get protein without too much saturated fat
Eat both animal and plant proteins
Go with beans
What are some menu items
you could consume?
Vegetarian diets
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Vegetarian diets
Reasons to be vegetarian: Limited land and/or resources
Health
Religion Personal ethics
Environmental concerns
Benefits: lower cost and healthier
Risks: amino acid, mineral, and B vitamin
deficiency
Well-Planned Vegetarian Diets Are Healthy
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Well Planned Vegetarian Diets Are Healthy
You dont need to eat any animal foods to stay healthy.By combining plant proteins containing different limitingamino acids you can get the right combinations ofamino acids to meet your protein needs
Vegetarian diets include a variety of eating patterns
Traditionally, vegetarianism is defined as abstinence frommeat, fish, and fowl, but the term has come to mean manydifferent things
Well-Planned Vegetarian Diets Are Healthy
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Well Planned Vegetarian Diets Are Healthy
Vegetarian diets can have nutritional, health, and economicadvantages
Vegetarians have been shown to have lower risks for obesity,diabetes, cardiovascular disease, high blood pressure, and sometypes of cancer
Despite the health and economic benefits of vegetarian diets,nutrient deficiencies can be a problem, particularly for peopleconsuming vegan diets
Vegetarian pyramids help you choose a meatless diet
Types of vegetarian diets
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Types of vegetarian diets
Semivegetarian: Excludes red meat but may includefish and poultry, as well as dairy products and eggs
Pescetarian: Excludes all animal flesh except fish
Lacto-ovo vegetarian: Excludes all animal flesh but
includes eggs and dairy products Lacto vegetarian: Excludes animal flesh and eggs but
includes dairy products
Vegan: Excludes all food of animal origin
Meeting dietary needs with a vegan diet
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Meeting dietary needs with a vegan diet
Meeting dietary needs with a vegan diet
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Meeting dietary needs with a vegan diet
Concept check
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Concept check
How can nitrogen balance be maintained?
What are benefits and risks of consuming a
plant-based diet?
How can vegetarians avoid nutrient
deficiencies?
Think critically
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Think critically
Sickle cell anemia is an inherited disease caused by anabnormality in the gene for the protein hemoglobin. It
causes red blood cells to take on a sickle shape.
Sickle cell hemoglobin differs from normal
hemoglobin by one amino acid. Why might this
difference change the shape of the hemoglobin?
Do you think sickle-shaped red blood cells can
travel easily through narrow capillaries?
How might this disorder affect the ability to get
oxygen to the bodys cells?
What are similarities and differences
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What are similarities and differences
between:
Proteins and amino acids?
Chromsomes and genes?
DNA and mRNA? Plant and animal proteins?
Kwashiorkor and marasmus?
Vegetarian and vegan diets?
Applications
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Applications
What advice could you give to a loved onabout protein consumption to decrease
disease risk?
Nutrition in the news
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Nutrition in the news
Atkins diets
Protein supplements for weight lifters
Checking student learning outcomes
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Checking student learning outcomes
How do proteins contribute to health anddisease?
What advice would you give to a loved one
about protein consumption?