Chapter 06: Protein

Janet eats beans, grains, fruits, and vegetables, and milk. Her diet is considered a. lactovegetarian. b. ovolactovegetarian. c. flexitarian. d. vegan.

ANS: A Diets than contain plant foods plus milk are lactovegetarian diets; ovolactovegetarian diets include milk and eggs. Vegan diets contain only plant foods. Diets that contain plant foods plus dairy, eggs, and occasional meat, fowl, or fish are flexitarian

High urinary urea excretion may be caused by a. high protein intake. b. phenylketonuria. c. kidney failure. d. administration of growth hormone

ANS: A High levels of urinary urea excretion may be caused by protein intake in excess of the body's need; excess protein is deaminated and used to provide energy; and the ammonia is converted to urea by the liver and excreted by the kidneys. Kidney failure causes high blood levels of urea because the kidneys are unable to excrete it; urinary urea levels would be low. Phenylketonuria is an inability to break down excess phenylalanine and would have very little effect on urea excretion. Administration of growth hormone would cause anabolism, which would result in greater use of amino acids and less urea excretion

The most important function of hydrochloric acid in the stomach is to a. convert pepsinogen to its active enzyme form, pepsin. b. denature dietary proteins to allow digestion. c. kill bacteria in food and prevent foodborne illness. d. stop the action of salivary amylase.

ANS: A Hydrochloric acid is essential in the stomach for activating pepsinogen to pepsin in order to begin protein digestion. The acid does denature some proteins, but this is not essential to digestion. Stomach acid may play a role in killing pathogenic bacteria and does stop the action of salivary amylase, but these effects are less important

Without vitamin B6, the body would be unable to a. absorb amino acids. b. digest proteins. c. convert ammonia to urea. d. regulate acid-base balance

ANS: A Vitamin B6 (pyridoxine) is needed as a carrier for absorption of amino acids. It has several roles in protein metabolism, but it is not needed for protein digestion or for conversion of ammonia from protein breakdown to urea in the liver. Pyridoxine is not involved in regulation of acid-base balance.

Some proteins contain an alpha helix, which is part of their _____ structure. a. primary b. secondary c. tertiary d. quaternary

ANS: B The alpha helix structure is an example of the secondary structure of proteins. The primary structure is the amino acid sequence. The tertiary structure comprises bonds that form within chains in loops or folds. Quaternary structure is formed by combinations of more than one polypeptide

A person who follows a strict kosher diet would not eat a. macaroni and cheese. b. a cheeseburger and fries. c. a bean-and-cheese burrito. d. roast beef with mashed potatoes.

ANS: B A strict kosher diet would not include a cheeseburger because meat and dairy may not be eaten together. Both macaroni with cheese and a bean-and-cheese burrito contain only dairy. Roast beef with mashed potatoes is acceptable as long as the beef has been slaughtered appropriately.

The property of protein that is most important to its buffering properties is a. its ability to create osmotic pressure in intravascular, intracellular, and interstitial fluids. b. the fact that amino acids include both an acid carboxyl group and an amine base group. c. its ability to pump nutrients and other vital substances across cell membranes. d. its communication (hormones) and catalytic (enzyme) functions that help regulate body functions

ANS: B All of these statements are true of proteins, but the condition that allows it to act as a buffer is the composition of amino acids that includes both an acid carboxyl group and an amine base grou

During acute bacterial infections, patients need extra protein to manufacture a. hormones. b. antibodies. c. antibiotics. d. enzymes.

ANS: B During bouts of infection, the immune system uses protein to produce antibodies. Hormones are chemical messengers in the body that are sometimes proteins but are not directly involved in fighting infection. Antibiotics help recover from bacterial infections but are administered to the patient and are not produced by the body. Enzymes are protein catalysts in the body and are also not involved in fighting infection.

If a person usually ate 2 ounces of lean meat at lunchtime and decided to substitute cooked lentils instead, how much of the lentils would the person need to eat? a. 2 tablespoons b. cup c. cup d. 1 cup

ANS: B Each ounce of meat is equivalent to cup cooked dry peas or lentils. Therefore, 2 oz of meat would be equivalent to cup

An example of the lifestyle habit of "chaining" is a. gradually reducing intake of sugar-sweetened beverages. b. eating a piece of fruit with breakfast every day. c. keeping a record of all food and beverages eaten. d. involving all family members in choosing healthy foods.

ANS: B Eating a piece of fruit with breakfast every day is an example of "chaining." Chaining involves linking two behaviors; soon the individual will always want to eat a piece of fruit whenever he or she eats breakfast. Gradually reducing intake of sugar-sweetened beverages, keeping a record of all food and beverages eaten, and involving all family members in choosing healthy foods are other good strategies to help improve eating habits.

A patient fell off a bicycle and broke one arm and one leg. Immediately after the accident, the patient's body will be in a state of a. anabolism. b. catabolism. c. deamination. d. hypermetabolism.

ANS: B Immediately after a serious accident, the physical stress, immobility, and need to break down damaged tissues cause loss of tissue through catabolism. Anabolism occurs when new protein is being formed during growth or healing. Deamination is one part of catabolism; it involves removal of the amino group when amino acids are broken down. Hypermetabolism is a term that describes an increased state of metabolism in general.

Eric follows a vegetarian eating pattern, and he wants to know whether he needs to take any vitamin and mineral supplements. What would be most important to find out? a. Whether he includes complementary vegetable proteins b. Whether he follows a vegan eating pattern or eats some animal foods c. Whether his skin has regular exposure to sunlight d. Whether he relies on mostly natural or mostly processed foods

ANS: B It would be important to find out whether Eric follows a vegan diet; strict vegan diets do not contain any vitamin B12 (found only in animal products) and vitamin D (obtained mostly from fortified milk). Including complementary vegetable proteins would improve the overall quality of his protein intake but would not affect his vitamin and mineral intake. Regular skin exposure to sunlight would help manufacture some vitamin D, but would not help with vitamin B12 status, and so the question of sun exposure is less important. Processed food may contain fewer micronutrients that natural foods, but this is less critical than whether he includes any animal foods in his diet.

The sports coaches at a university are designing training diets for their teams. Why do they need to provide more protein for the men's rowing team than for the women's rowing team? a. The men's team is more active than is the women's team. b. The men's team has more lean body mass than does the women's team. c. The men's team has a higher metabolic rate than does the women's team. d. The men's team uses dietary protein less efficiently than does the women's team.

ANS: B Men generally require more protein than do women because they have more lean body mass than do women; lean body mass requires more protein to maintain. Men are not necessarily more active than women when they compete in the same sport. They do have a higher metabolic rate, but this is because they have more lean body mass; their higher metabolic rate affects their energy needs, not their protein needs. Men do not use protein less efficiently than do women.

For clients with phenylketonuria the most important part of treatment is to a. not eat any foods that contain phenylalanine. b. limit their phenylalanine intake to the amount their bodies need. c. take enzyme supplements to help digest phenylalanine. d. take penicillin to prevent complications.

ANS: B People with phenylketonuria do need some phenylalanine to make essential proteins, but they should not take in more than they need because they will be unable to break down the excess. Phenylalanine is an amino acid, the smallest product of protein digestion, and so it is not digested by enzymes. Penicillin is used to prevent secondary infections in people with sickle cell anemia but is not used to treat phenylketonuria

An example of a meal that contains complementary proteins is a. pasta and tomato sauce. b. split pea soup with crackers. c. oatmeal and buttered toast. d. fruit yogurt with strawberries

ANS: B Split pea soup with crackers contains complementary proteins: The incomplete legume protein in the split pea soup complements the incomplete grain protein in the crackers. Vegetables such as tomato sauce and fruit such as strawberries do not contain sufficient protein to complement another incomplete protein in a meal. Both oatmeal and toast are grains, and so their incomplete proteins are not complementary. Fruit yogurt contains complete protein and does not need to be combined with an incomplete protein.

The RDA of protein for a healthy adult who weighs 60 kg is _____ g/day. a. 36 b. 48 c. 60 d. 72

ANS: B The RDA of protein for a healthy adult is 0.8 g/kg per day. Therefore, the RDA for an adult who weighs 60 kg is 48 g/day (0.8 60).

Nonessential amino acids can be made by the liver from a. glucose and urea. b. other amino acids. c. fatty acids and glycerol. d. enzymes and hormones.

ANS: B The body can make nonessential amino acids from other amino acids. Once the amino group has been removed from an amino acid and has been formed into urea, the body cannot turn it back into an amino acid. Fatty acids and glycerol cannot be used to make amino acids. Enzymes and hormones may help control the manufacture of nonessential amino acids but are not themselves used to make them

Body proteins may become denatured in the presence of a a. drug overdose. b. very high fever. c. vitamin deficiency. d. high stress level.

ANS: B Very high fever may denature body proteins because the extreme heat changes the shape of the protein. Drug overdoses, vitamin deficiencies, and high stress levels do not cause proteins to become denatured.

Most physically active adults in America do not need to eat more protein than inactive adults because a. exercise does not increase protein needs as long as energy needs are met. b. exercise increases the efficiency of recycling amino acids so that extra needs are met endogenously. c. most people have high enough protein intake to provide the extra protein needed for active muscles. d. most Americans are not sufficiently active to cause an increase in protein requirements.

ANS: C Athletes have higher protein needs than nonathletes (1.2 to 1.7 g/kg versus 0.8 g/kg, respectively). However, most Americans consume the amount of protein recommended for athletes, and so most American athletes do not need to increase their protein intake. Exercise does not increase the efficiency of protein turnover

The most accurate statement about amino acids is that a. most amino acids contain sulfur. b. they are stored in the liver for use when needed. c. essential amino acids cannot be manufactured by body cells. d. nonessential amino acids cannot be manufactured body cells

ANS: C Body cells cannot manufacture essential amino acids. Cells can make nonessential amino acids from essential amino acids. The liver is not able to store significant amounts of amino acids. Some but not most amino acids contain sulfur.

Examples of individuals who may have an increased risk for malnutrition include a. inactive middle-aged men. b. sleep-deprived adolescents. c. children with chronic infections. d. breastfed infants.

ANS: C Chronic infection at any age and especially in childhood increases the risk of malnutrition because nutrient needs may be higher and nutrients may not be so well absorbed. Also, appetite may be lower. Inactivity in middle-aged men is likely to lead to overnutrition, not undernutrition. Sleep-deprivation in adolescents is not associated with malnutrition. Breast-fed infants are usually well nourished and are not at high risk for malnutrition.

If a patient has a torn ligament, then during healing and recovery, the patient's body would need to manufacture a. fibrin. b. albumin. c. collagen. d. hemoglobin.

ANS: C Collagen is the main structural protein found in ligaments and other connective tissues, bone, and teeth. Fibrin is an important protein in blood clots. Albumin is an important blood plasma protein. Hemoglobin is the main protein that carries oxygen in the blood.

The protein found in muscles whose function is similar to that of hemoglobin in blood is a. collagen. b. oxyglobin. c. myoglobin. d. myosin.

ANS: C Hemoglobin carries oxygen in blood; the protein that carries oxygen in muscles is myoglobin. Myosin is a contractile protein found in muscles, and collagen is a structural protein found in ligaments and tendons. "Oxyglobin" does not exist.

An example of a food that contains complete protein is a. oatmeal. b. lentil soup. c. peanut butter. d. hard-boiled egg.

ANS: D Eggs and most other animal foods contain complete protein. Grains, legumes, and nuts contain incomplete proteins

High levels of glucocorticoid hormones are likely to be produced by someone who a. participates in a weight-training program. b. consumes excessive amounts of protein. c. is pregnant. d. has a large infected wound

ANS: D Glucocorticoid hormones are produced by the adrenal cortex and have a major role in protein catabolism. For an infected wound, catabolism is necessary to break down damaged tissue. Weight training and pregnancy are anabolic conditions. Consuming excessive amounts of protein places a burden on the kidneys for excretion of nitrogenous waste but does not affect glucocorticoid hormone levels

An example of a situation in which nitrogen balance is positive is a. aging. b. infection. c. starvation. d. pregnancy.

ANS: D Positive nitrogen balance means that more nitrogen is retained in the body than is excreted. This would be the situation in pregnancy, when new tissue is being formed in the mother and fetus. Aging, infection, and starvation are all times when the nitrogen balance would be negative.

If a man weighs 190 lb and eats 150 g protein per day, his protein intake is _____ of the Recommended Dietary Allowance (RDA). a. less than 100% b. between 100% and 150% c. between 150% and 200% d. greater than 200%

ANS: D The RDA for protein is 0.8 g per kilogram of body weight. This man's weight is 190 lb, or 86 kg; 86 kg 0.8 = 69.1 g protein per day. Thus, an intake of 150 g is more than twice his RDA of 69.1 g of protein per day.

If a person were to eat a diet that provided carbohydrate, fat, and micronutrients, but very little protein, for example if he or she ate only whole-wheat pita bread with olive oil, a. the body would manufacture amino acids to make essential proteins from fatty acids and glycogen. b. body metabolism would decrease to conserve amino acids until protein intake was resumed. c. the liver would recirculate amino acids instead of breaking them down and excreting urea. d. the body would break down muscle tissue to provide amino acids to make essential proteins

ANS: D The body needs regular dietary protein to provide amino acids. If no protein is eaten in the diet, the body uses muscle tissue to provide amino acids to make essential body proteins. The liver cannot recirculate amino acids; some are always broken down, and the nitrogen portion is excreted as urea. Body metabolism may decrease slightly, but it would not be sufficient to conserve amino acids for any length of time. The body cannot manufacture amino acids from fatty acids and glycogen.

A small child has normal weight, but his arms and legs are thin, whereas his belly and face appear swollen. His mother tells you that the only food they have had in the house for the past 3 weeks is noodles and some bread. The child probably has a. malabsorption syndrome. b. acute infection. c. marasmus. d. kwashiorkor.

ANS: D The child probably has kwashiorkor caused by inadequate protein intake with adequate energy intake (noodles and bread provide carbohydrate but little protein). Marasmus is caused by inadequate intakes of both energy and protein and is characterized by extreme wasting in the entire body. Acute infection or malabsorption syndromes may exacerbate malnutrition but are not the primary cause.

An appropriate size serving of meat, poultry, or fish is about the size of a. your fist. b. a dollar bill. c. the palm of your hand. d. one fourth of a dinner plate.

aNS: C An appropriate size serving of meat, poultry, or fish is about the size of the palm of your hand. This represents about 3 ounces. A serving the size of a fist or one fourth of most dinner plates would be too large. A dollar bill is flat and therefore does not indicate a three-dimensional serving size.