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PROTEINS
Chapter 7
Building Blocks of Proteins?
NH2
R
O
C
C
OH
H
Amine group
R group
Carboxylic Acid group
Examples of Amino Acids
Essential versus Non-essential
Limiting Amino Acid
C is the limiting amino acid in this example
CCCCC
AAAAAAAA
RRRRRR
CAR CAR CAR
CAR CAR
R
A A A
Limiting Amino Acids
Complementary Protein
Food 1
CC
AAAA
RRR
Food 2
CCCC
AA
RRR
CAR CAR CAR
CAR CAR CAR
Dietary Aspects
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PKU = Phenylketonuria

Vegetarian Diets
Protein Synthesis

Step 1:
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Step 2:
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Transcription
Processing
Step 3:
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Translation
Transcription
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Formation of RNA from DNA template
DNA=
A
C
T
G
A
T
RNA=
U
G
A
C
U
A
CODON #1
CODON #2
Condensation Synthesis
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Peptide bond
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Dipeptide
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Tripeptide
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Oligopeptide
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Polypeptide
Levels of Protein Structure
Sickle Cell Anemia
Denaturation of Protein
Turnover and Metabolism
Protein Digestion
Absorption of Amino Acids
Functions of Proteins

Supplies nitrogen in a
useable form

Structural components

Blood clotting

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Maintain fluid and
acid/base balance
Immune function
Functions of Proteins
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Hormones and enzymes
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Insulin and Thyroxine
Pepsin, Trypsin
Visual processes
Formation of glucose
(Gluconeogenesis)
Energy Source (4 kcal/energy)
RDA for Protein

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Promotes equilibrium
0.8 gm of protein / kg of healthy body weight
154 lb.
= 70 kg
2.2 kg/lb.
70 kg x
0.8 g protein
= 56 g protein
kg healthy body wt
Proteins in Foods
Proteins in Foods

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Americans tend to
eat more animal
protein than plant
protein (70%)
There are many
benefits to eating
more plant proteins:
Plant Protein

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No cholesterol
Low in saturated fat
High in (soluble) dietary fiber and
phytochemicals
HOWEVER:

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Somewhat less efficient (than
animal protein)
Lacking in one or more essential
amino acid
Protein-Energy Malnutrition
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Types of PEM:

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Kwashiorkor
Marasmus
Causes:
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Famine
Anorexia
Intestinal disorders
Kwashiorkor
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Low protein density
diet
Energy needs are
marginally met
Subcutaneous fat is
present
Poor growth, edema,
weakness, apathy,
diarrhea, listlessness
Marasmus

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Starving to death
“skin and bones”
appearance
Insufficient protein,
energy, nutrients
Little or no
subcutaneous fat
Reduce brain growth
Nutrition Perspective
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Vegan - primarily eats only plant foods
Fruitarian - primarily eats fruits, honey,
and vegetable oils
Lactovegetarian - consumes plant
products and dairy products
Lactoovovegetarian - consumes plant
products, dairy products, and eggs