Study Guide 6 – Introduction to Protein
Nutr 12
Protein and Amino Acid Functions
Describe the different ways in which proteins and amino acids function in the body. Give examples
of proteins in each category shown below. List some roles of intact amino acids in the body
 Body structure
 Movement (muscle contraction)
 Catalysis
 Transport
 Signaling between tissues/organs
 Defense
 Blood clotting
 Fluid balance
 Acid-base balance
Define: edema
Protein Structure
Describe the structures of amino acids, dipeptides, and proteins.
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Describe the “amine group”, “acid group”, and “side groups” of an amino acid. Which
chemical element is provided by proteins that is absent from the other energy nutrients?
About what fraction of the amino acids in proteins are essential? Give examples of essential
and nonessential amino acids.
Explain how the sequence of amino acids in a protein determines its ultimate shape,
characteristics, and role in the body.
Protein Synthesis
Which macromolecule provides the basic information (or “code”) that determines a protein’s
structure? Where is this type of molecule located in the cell?
Outline the process by which a protein is produced in the cell. Identify the roles of DNA, messenger
RNA (mRNA), transfer RNA (tRNA), and ribosomes.
 What would be the effect of a genetic mutation on the protein’s primary structure? Describe
the underlying defect in sickle cell anemia.
 Why must all essential amino acids be available during protein synthesis? What would
happen if one were unavailable – could the protein be made?
Define: genetic code, DNA, chromosome, gene, transcription, translation
Protein and Amino Acid Metabolism
How are amino acids used in the body? Compare the possible fates of the carbons in the amino
acids those of the nitrogen.
Describe how amino acids enter and exit the amino acid “pool.” Are amino acids and proteins
“stored” anywhere in the body? How are excess amine groups excreted?
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Are protein supplements or much higher protein intakes suggested for faster muscle-building?
Faster hair-growing? Improved immune function? What happens to the extra protein you eat?
New terms: deamination, transamination, glucogenic amino acids, lipogenic (ketogenic) amino
acids, protein turnover, urea
Figure: Protein Turnover
Nitrogen Balance
Compare "nitrogen equilibrium", "positive nitrogen balance" and "negative nitrogen balance" and
name circumstances when each might occur.
Into which category of nitrogen balance would you place healthy, non-growing adults? Would that
change if they should begin to eat excessive amounts of protein?
Describe a simple experiment that could be done to determine an individual’s protein requirements.
Protein Nutrition
What is the protein RDA for adults? Know how to use this value to determine a person’s specific
protein recommendation. Is the adult RDA value equally applicable for lean and obese individuals?
Identify the range of protein intakes suggested for adult men and women.
Explain why a low intake of calories (for example: when a person goes on a reducing diet) could
lead to negative nitrogen balance.
List some foods that are good sources of protein. Compare the protein content of a 3 oz serving of
meat, 1 cup of milk, and 1 slice of bread. Which has the most protein? The least?
Describe the two main factors that influence protein quality. Which foods generally supply higher
quality proteins, plant proteins or animal proteins?
 Why does a person need to get all of the essential amino acids in the diet regularly?
 Compare foods that supply high-quality proteins with those that provide lower quality
proteins. Explain why you selected these foods.
 Define: limiting amino acid, and identify the limiting amino acids in grains and legumes.
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Define: protein complementarity. Give examples of complementary proteins.
 Do complementary proteins need to be consumed in one meal for best use of the proteins
in these foods?
 Is a peanut butter sandwich a good example of complementary proteins? Explain your
answer.
Vegetarian Diets
Explain the differences among the different types of vegetarian diets. Be able to characterize
lacto-ovo vegetarian diets, lacto vegetarian diets, and vegan diets. Are there any advantages to
consuming a vegetarian diet?
Is protein a problem nutrient for people on vegetarian diets? Are animal proteins “better for us” for
some reason than plant proteins?
Which nutrients are the main nutrients of concern for many vegetarians?
Protein-Energy Malnutrition (PEM)
Describe the conditions of marasmus and kwashiorkor. What are their clinical effects?
Be able to link the symptoms of kwashiorkor with the loss of specific body proteins in individuals
with this condition.
Protein Excess
What are some potential problems associated with excessive protein consumption?
Health Problems Related to Proteins/ Amino Acids
 Food Allergies
List foods that commonly cause food allergy. What causes a food allergy? Which
age group is most susceptible? Are food allergies outgrown in time?
What are common symptoms of food allergy? Contrast food allergies with food
intolerances (like lactose intolerance).
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Phenylketonuria (PKU)
Describe the condition of phenylketonuria (PKU). What are its potential effects in
untreated individuals?
Explain why the use of foods sweetened with aspartame is discouraged for an
individual with PKU.
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