Chapter Four: Proteins and
Amino Acids
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Explain how the chemical structure of
proteins differs from the other energy
nutrients
Identify and describe the multiple functions of
protein in the body
Explain the difference between essential and
non-essential amino acids
Describe the concept of nitrogen balance
Proteins cntd.
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Describe conditions associated with
either positive or negative nitrogen
balance
Describe causes and characteristics of
marasmus and kwashiorkor
Explain what makes a protein complete
and identify sources of them
Explain the types of vegetarian diets
What do you already know?
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Proteins in Review
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Energy provided: 4 kcal per gram
12-15% of calories per day
Sources in the Food Guide Pyramid
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Bread, Cereal, Rice and Pasta Group
Vegetable Group
Milk, Yogurt and Cheese Group
Meat and Meat Alternates Group
Chemical View of Protein
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Contains same elements as other
energy nutrients (carbon, hydrogen and
oxygen) plus nitrogen
Made up of building blocks called amino
acids (20 amino acids)
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Essential amino acids must be supplied in
foods (9 are essential)
Non-essential am. acids—body can make
Nutritional Role of Proteins
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Primary function is to Build, Maintain,
and Repair the Body — not to provide
energy
Enzymes: catalysts that facilitate
chemical reactions
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Anabolic—build body compounds
Catabolic—dismantle body compounds
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Example—digestive enzymes
Nutritional Roles cntd.
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Fluid and Electrolyte Balance
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Help maintain distribution of fluids in the
body
Proteins are hydrophilic—water loving
Acid-Base Balance
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Controls blood pH (acidity or alkalinity)
Release or bind hydrogen ions
Protein roles cntd.
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Antibodies
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Hormones
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Formed from protein
Maintains resistance to disease
Messenger molecules
Examples are insulin and thyroxin
Transport—carry other nutrients, e.g.
oxygen, lipids, vitamins and minerals
Protein Roles cntd.
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Nitrogen Balance—maintenance of
same amount of protein in body tissues
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Positive Balance—nitrogen in > nitrogen
out
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Growing children
Pregnant woman
Negative Balance—nitrogen in < nitrogen
out
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Fasting or starvation
Severe traumas—burns, tissue loss
Protein Roles cntd.
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Zero balance
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Nitrogen in = nitrogen out
Normal daily functioning
Measured by sample of body tissue or
urine
Protein Deficiency
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Marasmus
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Energy deficiency common in young
children ages 6-18 months
Food is low in kcalories and protein
Kwashiorkor: (Red hair)
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Protein deficiency common in children after
age two—after weaning
Symptoms: edema, distended abdomen
and orange hair
Proteins in Foods
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Complete Proteins:
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Contain all essential amino acids
Sources are animal foods with the
exception of gelatin
Incomplete Proteins:
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Limited in amounts or number of essential
amino acids
Sources are grains, vegetables and
legumes
Protein Sparing
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Carbohydrate needed to spare protein
from being used for energy
If protein is used for energy it is
deaminized—nitrogen is removed—and
the C, H, and O are used for energy
Low carbohydrate diets are not
recommended for this reason
Vegetarian Diets
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Vegetarianism: rely mostly on non animal
foods for their diet
Levels of Vegetarianism
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Lacto-vegetarians—milk only
Lacto-ova—milk and eggs
Vegans—exclude all animal products
Advantages:
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Easier to maintain desired weight
Lower cholesterol and higher fiber foods
Lower rates of colon cancer and heart disease
Better digestion—low fat and high fiber
Vegetarian Pyramid
Vegetarianism cntd.
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Nutritional concerns
Vitamin B12 only found in animal
products
 Vitamin D mainly available in milk and
animal fats
 Iron and Zinc are not as available in
non-animal sources
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TEST Questions
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1. Proteins are chemically different
from carbohydrates and fat because
they also contain:
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A.
B.
C.
D.
Phosphorus
Sodium
Iron
Nitrogen
Test Questions
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4. The basic building blocks of protein
are:
a. glucose units
b. amino acids
c. side chains
d. saturated bonds