Download Chapter 6 Proteins and Amino Acids Important Math Calculations

Chapter 6
Proteins and Amino Acids
Important Math Calculations
Nitrogen balance = ____ g of nitrogen intake – ___ g of nitrogen output
Converting weight in pounds to kilograms: ____ lbs  2.2 = ___ kg
Calculating the RDA for protein for adults: ____ weight in kg  0.8 = ___ g protein daily
There are several methods of determining protein quality including the following:
Chemical score =
mg of essential amino acid in food
mg of essential amino acid in reference food
Protein Efficiency Ratio =
weight gain in g
protein intake in g
Net Protein Utilization =
Biological Value =
nitrogen retained
 100
100 nitrogen intake
nitrogen retained
 100
100 nitrogen absorbed
PDCAAS = chemical score 3% digestibility of the protein
Chapter Outline
I. Why Is Protein Important? *Many vital compounds are proteins, including enzymes,
hormones, transport proteins, and regulation of both acid-base and fluid balance.
II. Amino Acids Are the Building Blocks of Proteins (Table 6.1). *Proteins are long chains of
amino acids. Amino acids are composed of a central carbon atom bonded to carboxyl, amino,
and side groups.
A. Amino acids are identified by their side groups. *At least 20 amino acids are
important in human nutrition; 9 of these amino acids are considered essential (must
come from the diet), while the body can make the other 11 (nonessential) amino acids.
B. Protein structure: unique three-dimensional shapes and functions (Figure 6.3). *The
amino acid sequence of a protein determines its shape and function.
1. Amino acid sequence
2. Protein shape
C. Protein denaturation: destabilizing a protein’s shape (Figure 6.4). *Denaturing of
proteins changes their shape and therefore their functional properties.
Key terms: wasting, essential amino acid, nonessential amino acid, conditionally essential amino
acid, peptide bond, dipeptide, oligopeptide, hemoglobin, hydrophilic amino acids, hydrophobic
amino acids, disulfide bridge, denaturation
III. Functions of Body Proteins
A. Structural and mechanical functions (Figure 6.6)
B. Enzymes (Figure 6.7A and Figure 6.7B)
C. Hormones (Figure 6.8)
D. Immune function
E. Fluid balance (Figure 6.10)
F. Acid-base balance (Figure 6.11)
G. Transport functions
H. Source of energy and glucose
Key terms: collagen, keratin, motor proteins, antibody, immune response, extracellular fluid,
interstitial fluid, intravascular fluid, edema, pH, buffer, acidosis, alkalosis, deamination
IV. Protein Digestion and Absorption
A. Protein digestion (Figure 6.14). *Protein digestion begins in the stomach through the
action of hydrochloric acid and the enzyme pepsin.
1. In the stomach
2. In the small intestine
3. Undigested protein
B. Amino acid and peptide absorption (Figure 6.15). *Proteins are completely digested in
the small intestine and absorbed by facilitated diffusion and active transport.
Key terms: precursor, protease, proenzyme, trypsin/trypsinogen, chymotrypsin/chymotrypsinogen, peptidases, celiac disease, cystic fibrosis
V. Proteins in the Body
A. Protein synthesis (Figure 6.16)
B. The amino acid pool and protein turnover (Figure 6.17)
C. Synthesis of nonprotein molecules
D. Protein and nitrogen excretion
E. Nitrogen balance (Figure 6.18)
Key terms: DNA, messenger RNA, ribosomes, transfer RNA, ribosomal RNA, amino acid pool,
protein turnover, neurotransmitter, urea, positive nitrogen balance, negative nitrogen balance,
nitrogen balance, nitrogen equilibrium
VI. Proteins in the Diet. *Dietary protein is found in meats, dairy products, legumes, grains, and
vegetables. In general, animal foods contain higher quality protein than what is found in plant
foods.
A. Recommended intakes of protein. *Protein needs are highest when growth is rapid,
such as during infancy, childhood, and adolescence.
1. Adults
2. Other life stages (Table 6.2)
3. Physical stress
B. Protein consumption (Table 6.3). *The protein intake of most Americans exceeds their
RDA.
C. Protein quality
1. Complete proteins
2. Incomplete and complementary proteins (Table 6.4)
D. Evaluating protein quality
1. Chemical, or amino acid, scoring
2. Protein efficiency ratio
3. Net protein utilization
4. Biological value
5. Protein digestibility corrected amino acid score
E. Estimating your protein intake
F. Proteins and amino acids as additives and supplements
Key terms: complete protein, incomplete protein, complementary protein, chemical scoring,
amino acid scoring, limiting amino acid, protein efficiency ration, net protein utilization,
biological value, protein digestibility corrected amino acid score, protein hydrolysate
VII. Vegetarian Eating
A. Why people become vegetarians
B. Types of vegetarians (Table 6.6)
C. Health benefits of vegetarian diets
D. Health risks of vegetarian diets
E. Dietary recommendations for vegetarians
VIII. The Health Effects of Too Little or Too Much Protein
A. Protein-energy malnutrition (Figure 6.20). *Protein deficiency is most common in
developing countries and results in the conditions known as marasmus and kwashiorkor.
1. Kwashiorkor
2. Marasmus
3. Nutritional rehabilitation
B. Excess dietary protein (Figure 6.21). *Protein excess is also harmful and may affect
risk for osteoporosis, heart disease, and cancer.
1. Kidney function
2. Mineral losses
3. Obesity
4. Heart disease
5. Cancer
6. Gout
Key terms: protein-energy malnutrition, kwashiorkor, marasmus, gout
Classroom Activities
ACTIVITY 1: VEGETARIAN DIETS: FACT OR FALLACY?
This activity can be used for both small and large classes. The instructor can put the following
statements about vegetarianism on the board, on an overhead transparency, or a PowerPoint
slide:
1. Vegetarian diets do not provide enough protein and other essential nutrients.
ANSWER: Fallacy. With careful planning, a diet that contains no animal products can be
nutritionally complete and can also offer many health benefits.
2. The main reason individuals become vegetarian is because of religion.
ANSWER: Fallacy. There are many reasons people become vegetarians such as health reasons,
necessity, concern for the environment, a desire to reduce world hunger and make better use of
scarce resources, an aversion to eating another living creature, or concerns about cruelty to
animals.
3. All vegetarians include no meat in their diet.
ANSWER: Fallacy. There are many different types of vegetarians including: semi-vegetarians,
pesco-vegetarians, lacto-ovo-vegetarians, lacto-vegetarians, ovo-vegetarians, vegans, and
fruitarians.
4. Vegetarian diets usually contain less fat, saturated fat, and cholesterol than nonvegetarian
diets.
ANSWER: Fact
5. Vegetarians usually weigh less for their height than nonvegetarians.
ANSWER: Fact. Vegetarians usually weigh less because their diets provide less energy. Other
healthful lifestyle factors may add to this.
6. Semi-vegetarian diets are the most lacking in vital nutrients.
ANSWER: Fallacy. Vegan diets are the most restrictive.
7. The vitamin that must be supplemented in vegan diets is vitamin C.
ANSWER: Fallacy. Vitamin B12 must be supplemented.
8. Vegetarians may use soy products as a source of complete protein in their diet.
ANSWER: Fact
9. Vegans consume more heme iron in their diets than nonheme iron.
ANSWER: Fallacy. Plant foods contain a form of iron called nonheme iron that is not as well
absorbed as the heme iron in animal foods.
The students then have to decide whether the statements are fact or fallacy and explain why. As
each statement is analyzed, the instructor can expand on why it is or is not a fact. For smaller
classes, this activity works well when students get into groups and discuss all statements
presented.