Download Proteins

What Are Proteins?

Proteins: large, complex molecules
composed of amino acids
 DNA determines structure
Contain nitrogen
 20 different amino acids (AA) are used
to make proteins

 Building blocks of proteins
Amino Acids

Amino acids are
linked (bound)
together by special
chemical bonds:
 Peptide bonds

The 20 amino acids
can be bound
together to make up
to 50,000 different
protein molecules
Amino Acids

The structure of an amino acid begins
with a central carbon atom.
 4 attachment sites

The central carbon is surrounded by:
1. a hydrogen atom
2. an acid group
3. an amine group
Identical on every
amino acid
4. a side chain (R group) that is unique to
each amino acid
○ Variations give each AA its distinct properties
Amino Acids
Amino Acids

Essential amino acids: cannot be
produced by our bodies
 Must be obtained from food
 9 amino acids

Nonessential amino acids: can be
made by our bodies
 Using parts of nitrogen of other amino acids
○ Transamination
 11 amino acids
Amino Acids
Conditionally essential amino acids: when nonessential amino acids can’t
be made to meet body needs
How Are Proteins Made?
Proteins are long chains of amino acids.
 Amino acids are joined to each other by
peptide bonds.
 The structure of each protein is dictated
by a DNA of a gene.

 Genes carry the instructions for amino acid
sequencing
How Are Proteins Made?

Dipeptide
 Two amino acids

Tripeptide
 Three amino acids

Oligopeptide
 Four to forty nine amino acids

Polypeptide
 50 to 100 amino acids
 Results in complex shapes
Proteins Organization

The three-dimensional shape of a
protein:
 is determined by the amino acids in the
protein
 is critical to the proper function of the protein
○ Tendons vs. red blood cells
 can uncoil due to damage by heat, acids,
heavy metals, alcohol, and other substances
○ Denatured protein = lost function
 **Denaturation**
Protein Structure Example
Protein Structure Example
Sickle-shaped cell
Protein Denaturation
Why Do We Need Proteins?

contribute to cell growth, repair, and
maintenance
 Growing children, damaged cells, new cells
Why Do We Need Proteins?

act as enzymes and hormones
 Inborn errors of metabolism (IEOM)
Galactosemia
Enzymes
Why Do We Need Proteins?

help maintain fluid balance
 Proteins help pull fluids out of tissues into
blood vessels and cells
○ If insufficient protein intake: edema
Why Do We Need Proteins?

Transport nutrients
 Electrolytes, vitamins, minerals, glucose

Help maintain pH balance
 Act as buffers against acids and bases

Protect against disease
 Antibodies

Serve as an energy source
 Gluconeogenesis
 We want to “spare” protein
Proteins in the Diet

Our bodies do not store proteins, but
they do have a small supply of amino
acids in reserve
 Pool of amino acids

All essential amino acids need to be in
the pool
 Limiting amino acid – essential amino acid
that is missing or in shortest supply
○ May slow or halt protein synthesis (video)
Limiting Amino Acids
Proteins in the Diet
Most proteins contain all of the essential
amino acids (EAAs)!! (except gelatin)
 Complete proteins supply all the EAAs
needed to meet biologic requirements
when consumed at recommended amounts

 “high quality”
 Animal-based, except soybeans/quinoa

Incomplete proteins also supply all of the
EAAs, but usually one AA is limiting (low)
 “low quality”
 Plant-based
Proteins in the Diet

: using two incomplete
proteins together to make a complete protein
The 2 incomplete proteins that supply all EAAs:
: two protein sources that
together supply all nine essential amino acids in
adequate quantities
 Do not have to be eaten at the same time
 Examples?
 Who might this be important for?
Proteins in the Diet
Soy Foods
High quality, complete protein
 Contain vitamins, minerals,
phytochemicals
 What about estrogen/hormones?

 Isoflavones not same as human estrogen
 Will not turn guys into gals

Up to 3 servings per day
Protein Supplementation
Muscle growth =
PRO synthesis > PRO breakdown
 Achieved with weight training and
regular meal consumption

 PRO + CHO
Eating excess protein does not lead to
muscle gain
 May be helpful for certain people

How Much Protein Should We
Eat?

Proper protein intake depends on:

age
 activity level
 health status

Dietary Reference Intake (DRI)
 0.8 g protein per kg body weight (most adults)
 1.2-1.7 g/kg for athletes
 10% – 35% of total energy intake should be
from protein (AMDR)
How Much Protein Should We
Eat?
To convert pounds to kg, simply divide
by 2.2
 A person weighing 160 pounds is how
many kg?

 160 lbs ÷ 2.2 = ~73 kg

If this person is an average adult, what
is his/her PRO requirement?
 73 kg x 0.8 g PRO/kg = 58 g PRO/day
How Much Protein Should We
Eat?

People who require more protein
include:
 children
 adolescents
 pregnant or lactating women
More needed
for growth
and
development
 Athletes
○ Carry more O2, make glucose, repair/make
new tissue
 Vegetarians (some)
○ Plant proteins less well digested
Sources of Protein

Good sources of protein include:




meats
dairy products (milk, egg whites)
soy products (considered “complete”)
legumes (all varieties of dried beans, peas,
peanuts)
○ Also considered a veggie choice!!
 whole grains (compliment the legumes)
 Nuts
 (Don’t discount leafy greens)
Vegetarian Diets



Vegetarianism:
focusing the diet on
foods of vegetable
origin (including
fruits, grains, nuts)
There are many
versions of
vegetarianism.
There are many
reasons to adopt a
vegetarian diet.
Vegetarian Diets
Why Vegetarianism?

People choose vegetarianism for:
 ethical reasons
 concerns over food safety/antibiotics
 ecological reasons
 religious reasons
 health benefits
Health Benefits of Vegetarianism

Reduced risk of:
 obesity, type 2 diabetes
 heart disease and high blood pressure
 some types of cancer
 kidney disease, kidney stones, gallstones
Fewer digestive problems
 Current guidelines emphasize eating
plant protein sources

Considerations of Vegetarianism
Vegetarian diets can be low in some
vitamins and minerals.
 Vegetarians (and everyone else) must
carefully plan a balanced and adequate
diet.
 Vegetarians (and everyone else) can
use soy products as a protein source.

Diet Comparison
Nutrients of Concern
Nutrients of Concern
1.
Potassium
1.
Vitamin B12
2.
Vitamin A
2.
Zinc
3.
Vitamin C
3.
Calcium
4.
Vitamin E
4.
Vitamin D
5.
Vitamin K
5.
Iron
6.
Fiber
7.
Calcium
8.
Vitamin D
9.
Iron
S.A.D (Standard American
Diet)
Vegetarian/Vegan
Vegetarian Food Guide Pyramid
Vegetarian Eating Guides
PCRM’s Power Plate
Vegetarian Society of the
United Kingdom
Protein Imbalances

Too little protein:
 Protein-energy malnutrition (PEM)
○ Marasmus
○ Kwashiorkor
○ Due to poverty, chronic disease, eating
disorders

Too much protein
Marasmus





Starving to death
Insufficient PRO,
energy, & nutrients
Little to no
subcutaneous fat
Reduced brain
growth
Also seen in
hospitalized patients
Kwashiorkor




Not enough protein
Energy needs just
marginally met
Swollen abdomen
Impaired growth,
rash, impaired
immune system,
fatty liver
Too Much Protein
Do not exceed 2 grams/kg body weight
 Why not?

 Not getting enough plant foods
 Risk imbalances in diet
Can You Eat Too Much Protein?
The risks of too much protein may include:
 high cholesterol and heart disease
 Due to high saturated fat, low fiber intakes

possible bone loss
 High-protein diets may cause excess
calcium excretion leading to bone loss.
Can You Eat Too Much Protein?

The risks of too much protein may also
include kidney disease.
 High-protein diets can be difficult for people
with kidney problems.
○ Due to the demand placed on stressed
kidneys to flush out excessive urea
 There is no evidence that high-protein diets
cause kidney disease in healthy people.

Increased cancer risk?
RD Chuckle