Chapter 6: Proteins and Amino Acids

What are some dietary recommendations that you could provide for vegetarians to maintain a balanced diet? Provide three recommendations.

(1) Choose a variety of foods, including whole grains, vegetables, fruits, legumes, nuts, seeds, and, if desired, dairy products and eggs. (2) Choose whole, unrefined foods often and minimize intake of processed foods, highly sweetened, fatty, and heavily refined foods. (3) Choose a variety of fruits and vegetables. (4) If animal foods such as dairy products and eggs are used, choose lower-fat dairy products and use both eggs and dairy products in moderation. (5) Include a regular source of vitamin B12 and, if sun exposure is limited, of vitamin D.

A high-quality protein does all of the following except: A. Supply all the essential amino acids in amounts needed by the body. B. Provide enough amino acids to supply nitrogen for nonessential amino acid synthesis. C. Regulate blood sugar levels. D. Is easy to digest.

Regulate blood sugar levels.

Based on the RDA for protein intake, an 80-kg adult would need approximately ________ grams of protein a day.

80 × 0.8 = 64 grams

What are some of the health benefits and risks associated with vegetarian diets?

Answers may vary. Vegetarians tend to have a lower risk of diabetes, cancer, and all-cause mortality. However, poorly planned vegetarian diets can be low in many nutrients (e.g., iron, zinc, calcium, vitamin D, riboflavin, vitamin B12, and omega-3 fatty acids).

If nitrogen intake exceeds nitrogen excretion, the body is said to be in _____ nitrogen balance. A. Neutral B. Normal C. Negative D. Positive

Positive

Which of the following is not a role of proteins as additives in foods? A. Flavor enhancer B. Texturizer C. Stabilizer D. Preserver

Preserver

What food would be the best protein complement to rice in a meal? A. Whole-grain bread B. Applesauce C. Broccoli D. Red beans

Red beans

The liver converts ammonia into _____.

Urea

A person who does not consume any animal products is considered a: A. Pesco-vegetarian. B. Fruitarian. C. Vegan. D. Vegetarian.

Vegan

Toxic product of protein degradation

ammonia

Protein in raw eggs that interferes with biotin absorption

avidin

Abundant fibrous protein in connective tissue

collagen

Attraction between two amino acids

peptide bond

In maintaining proper acid-base balance, proteins act as: A. Hormones. B. Buffers. C. Antibodies. D. Enzymes.

Buffers

Carbohydrate and lipid are protein sparing because they: A. Provide more energy per gram than protein. B. Are the only sources of glucose for cells. C. Can reduce the need to use amino acids for fuel. D. Act as buffers in the blood instead of protein.

Can reduce the need to use amino acids for fuel.

_____ are protein catalysts for chemical reactions.

Enzymes

What are essential, conditionally essential, and nonessential amino acids? Provide two examples for each.

Essential amino acids are amino acids that your body cannot make and must be provided by the diet. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Conditionally essential amino acids are amino acids that are only essential under certain conditions. These include tyrosine and cysteine. Under normal circumstances, your body makes tyrosine from the essential amino acid phenylalanine, and cysteine from either methionine or serine. If a disease or condition interferes with your ability to synthesize tyrosine or cysteine from its amino acid precursors, then your body will need tyrosine or cysteine from the diet. Nonessential amino acids are amino acids that do not need to be provided by your diet because your body can make them. These include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.

True or False? Americans typically get most of their protein from plant foods.

False

People with celiac disease cannot digest _____, a protein found in grains.

Gluten

Food labels list the quantity of protein per serving in: A. Micrograms. B. Grams. C. Milligrams. D. Kilograms.

Grams

What is the role of hydrochloric acid (HCl) in protein digestion? What happens if HCl secretion is not adequate?

Hydrochloric acid plays an important role in denaturing and unfolding protein and making an amino acid chain more accessible to the action of enzymes. HCI also stimulates proenzyme pepsinogen to active enzyme pepsin. Thus, if an individual does not have an adequate amount of HCI secretion, he or she may experience indigestion.

Amino acids that are attracted to water are called _____.

Hydrophillic

Most proteins go through final digestion in the: A. Mouth. B. Stomach. C. Large intestine. D. Microvilli.

Microvilli.

Which food contains the most complete protein per serving? A. Milk B. Vegetable salad C. Apple D. Rice

Milk

Net protein utilization measures how: A. Easily nitrogen is converted to glucose. B. Much dietary protein the body retains and uses. C. Well the body recycles amino acids. D. Adequately the protein in a food is digested.

Much dietary protein the body retains and uses.

Define nitrogen balance and list two conditions of positive nitrogen balance and two conditions of negative nitrogen balance in the body.

Nitrogen balance is the nitrogen intake minus the sum of all sources of nitrogen excretion. Examples of positive nitrogen balance conditions are pregnancy and other periods of growth (infancy, childhood, and recovering from protein deficiency or illness). Examples of conditions that result in negative nitrogen balance include starvation, extreme calorie restriction, fever, severe illness, and infection.

PEM is seen in the United States predominantly among the following groups except: A. Obese persons. B. Cancer patients. C. AIDS patients. D. Anorexics.

Obese persons Protein-energy malnutrition (PEM) refers to a form of malnutrition which is defined as a range of pathological conditions arising from coincident lack of protein and/or energy in varying proportions.The condition vary in forms ranging from mild through moderate to severe degrees. Types include: Kwashiorkor (protein malnutrition predominant) Marasmus (deficiency in calorie intake) Marasmic Kwashiorkor (marked protein deficiency and marked calorie insufficiency signs present, sometimes referred to as the most severe form of malnutrition PEM is fairly common worldwide in both children and adults and accounts for 6 million deaths annually.[2] In the industrialized world, PEM is predominantly seen in hospitals, is associated with disease, or is often found in the elderly.[2]

What is the association between high intake of animal protein and cardiovascular health? Provide a potential explanation for this observation.

Research has shown that high intake of animal protein is associated with high blood cholesterol levels and greater risk of heart disease and stroke. Scientists suggest that foods high in animal protein are also high in saturated fat and cholesterol, which may contribute to the observed outcome. Whether protein alone—independent of fat—plays a role in the development of heart disease is less clear.

Which condition would increase a person's protein needs the most? A. Fever B. Severe burn C. Common cold D. Muscle-building activities

Severe burn

List the roles of protein in the body.

Structural and mechanical; enzymes; hormones; antibodies; fluid balance; acid-base balance; transport; channels and pumps; energy

True or False? Certain cancer (e.g., colon) has been linked to diets high in animal protein foods.

True

Alteration of a protein by unfolding the polypeptide chain

denaturation