Chapter 1 - Fuel Metabolism and Nutrition: Basic Principles

Question 1

The largest amount of stored energy in the body
(A) Protein
(B) Triacylglycerol
(C) Liver glycogen
(D) Muscle glycogen

Answer 1

The answer is B. Adipose triacylglycerols contain the largest amount of stored energy in humans, followed by protein (even though loss of too much protein will lead to death), muscle glycogen, and liver glycogen (see Table 1.1).

Question 2

The energy source reserved for strenuous muscular activity
(A) Protein
(B) Triacylglycerol
(C) Liver glycogen
(D) Muscle glycogen

Answer 2

The answer is D. Muscle glycogen is used for energy during exercise. The glycogen is degraded to a form of glucose that can enter metabolic pathways for energy generation. Because exercise is strenuous, muscle requires large amounts of energy, and this can be generated at the fastest rate by converting muscle glycogen to pathway precursors within the muscle. Liver glycogen will produce glucose that enters the circulation. Once in the circulation, the muscle can take up that glucose and use it to generate energy; however, the rate of energy generation from liver-derived glucose is much slower than that from muscle-derived glucose.

Question 3

The primary source of carbon for maintaining blood glucose levels during an overnight fast
(A) Protein
(B) Triacylglycerol
(C) Liver glycogen
(D) Muscle glycogen

Answer 3

The answer is C. Liver glycogenolysis is the major process for maintaining blood glucose levels after an overnight fast. The muscle cannot export glucose to contribute to the maintenance of blood glucose levels, and fatty acid carbons cannot be utilized for the net synthesis of glucose.

Question 4

The major precursor of urea in the urine
(A) Protein
(B) Triacylglycerol
(C) Liver glycogen
(D) Muscle glycogen

Answer 4

The answer is A. The nitrogen in amino acids derived from protein is converted to urea and excreted in the urine. Uric acid, another excretion product that contains nitrogen, is derived from purine bases (found in nucleic acids), not from protein.

Question 5

A 32-year-old male is on a weight- maintenance diet, so he does not want to lose or gain any weight. Which amino acid must be present in the diet so the patient does not go into a negative nitrogen balance?
(A) Alanine
(B) Arginine
(C) Glycine
(D) Threonine
(E) Serine

Answer 5

The answer is D. The lack of one essential amino acid will lead to a negative nitrogen balance due to increased protein degradation to supply that amino acid for the ongoing protein synthesis. Of the amino acids listed, only threonine is an essential amino acid (alanine can be synthesized from pyruvate [which can be derived from glucose], arginine is produced in the urea cycle using aspartic acid and the amino acid ornithine, glycine is derived from serine, and serine is derived from 3-phosphoglycerate, which can be produced from glucose).

Question 6

After a fast of a few days, ketone bodies become an important fuel
(A) Liver
(B) Brain
(C) Skeletal muscle
(D) Red blood cells

Answer 6

The answer is B. The brain begins to use ketone bodies when levels start to rise after
3 to 5 days of fasting. Normally, the brain will use only glucose as a fuel (most fatty acids cannot cross the blood–brain barrier to be metabolized by the brain), but when ketone bodies are elevated in the blood, they can enter the brain and be used for energy.

Question 7

Ketone bodies are used as a fuel after an overnight fast
(A) Liver
(B) Brain
(C) Skeletal muscle
(D) Red blood cells

Answer 7

The answer is C. Skeletal muscle oxidizes ketone bodies, which are synthesized in the liver from fatty acids derived from adipose tissue. As the fast continues, the muscle will switch to oxidizing fatty acids, which allows ketone body levels to rise such that the brain will begin using them as an energy source.

Question 8

Fatty acids are not a significant fuel source at any time
(A) Liver
(B) Brain
(C) Skeletal muscle
(D) Red blood cells

Answer 8

The answer is D. Oxidation of fatty acids occurs in mitochondria. Red blood cells lack mitochondria and therefore cannot use fatty acids. The brain will not transport most fatty acids across the blood–brain barrier (the essential fatty acids are a notable exception). Therefore, the brain cannot use fatty acids as an energy source. The brain does, however, synthesize its own fatty acids, and will oxidize those fatty acids when appropriate. Red blood cells can never use fatty acids as an energy source due to their lack of mitochondria.

Question 9

During starvation, this tissue uses amino acids
to maintain blood glucose levels
(A) Liver
(B) Brain
(C) Skeletal muscle
(D) Red blood cells

Answer 9

The answer is A. The liver converts amino acids to blood glucose by gluconeogenesis. The other substrates for gluconeogenesis are lactate from the metabolism of glucose within the red blood cells and glycerol from the breakdown of triacylglycerol to free fatty acids and glycerol. Neither the brain, nor the skeletal muscle, nor the red blood cell can export glucose into the circulation.

Question 10

This tissue converts lactate from muscle to a fuel for other tissues
(A) Liver
(B) Brain
(C) Skeletal muscle
(D) Red blood cells

Answer 10

The answer is A. Exercising muscle produces lactate, which the liver can convert to glucose by gluconeogenesis. Blood glucose is oxidized by red blood cells and other tissues. Only the liver and kidney (to a small extent) can release free glucose into the circulation for use by other tissues.

Question 11

A young woman (5’ 3” tall, 1.6 m) who has a sedentary job and does not exercise consulted a physician about her weight, which was 110 lb (50 kg). A dietary history indicates that she eats approximately 100 g of carbohydrate, 20 g of protein, and 40 g of fat daily.

What is this woman’s BMI?
(A) 16.5
(B) 17.5
(C) 18.5
(D) 19.5
(E) 20.5

Answer 11

The answer is D. The BMI is calculated by dividing the weight of the individual (in kilograms) by the square of the height of the individual (in meters). For this woman, BMI 5 50/1.62 5 19.5.

Question 12

A young woman (5’ 3” tall, 1.6 m) who has a sedentary job and does not exercise consulted a physician about her weight, which was 110 lb (50 kg). A dietary history indicates that she eats approximately 100 g of carbohydrate, 20 g of protein, and 40 g of fat daily.

According to the woman’s BMI, into
what classification does her weight and height place her?
(A) Underweight
(B) Normal range
(C) Overweight (preobese)
(D) Class I obese range
(E) Class II obese range

Answer 12

The answer is B. According to Table 1.2, a BMI of 19.5 places the woman at the lower end of the normal range. Underweight is indicated by a BMI of <18.5; preobesity occurs above a BMI of 25, but <30. Class I obesity is indicated by a BMI between 30 and 35, and class II obesity by a BMI between 35 and 40.

Question 13

A young woman (5’ 3” tall, 1.6 m) who has a sedentary job and does not exercise consulted a physician about her weight, which was 110 lb (50 kg). A dietary history indicates that she eats approximately 100 g of carbohydrate, 20 g of protein, and 40 g of fat daily.

How many calories (kcal) does this woman consume each day?
(A) 1,440
(B) 1,340
(C) 940
(D) 840
(E) 640

Answer 13

The answer is D. The woman consumes 400 calories (kcal) of carbohydrate (100 g x 4 kcal/g), 80 calories of protein (20 x 4), and 360 calories of fat (40 x 9) for a total of 840 calories daily.

Question 14

A young woman (5’ 3” tall, 1.6 m) who has a sedentary job and does not exercise consulted a physician about her weight, which was 110 lb (50 kg). A dietary history indicates that she eats approximately 100 g of carbohydrate, 20 g of protein, and 40 g of fat daily.

What is the woman’s approximate DEE in calories (kilocalories) per day at this weight?
(A) 1,200
(B) 1,560
(C) 1,800
(D) 2,640
(E) 3,432

Answer 14

The answer is B. This woman’s DEE is 1,560 calories (kcal). DEE equals BMR plus physical activity. Her weight is 110 lb/2.2 5 50 kg. Her BMR (about 24 kcal/kg) is 50 kg 3 24 5 1,200 kcal/day. She is sedentary and needs only 360 additional kcal (30% of her BMR) to support her physical activity. Therefore, she needs 1,200 1 360 5 1,560 kcal each day.

Question 15

A young woman (5’ 3” tall, 1.6 m) who has a sedentary job and does not exercise consulted a physician about her weight, which was 110 lb (50 kg). A dietary history indicates that she eats approximately 100 g of carbohydrate, 20 g of protein, and 40 g of fat daily.

On the basis of the woman’s current weight, diet, and sedentary lifestyle, which one of the following does the physician correctly recommend that she should undertake?
(A) Increase her exercise level
(B) Decrease her protein intake
(C) Increase her caloric intake
(D) Decrease her fat intake to ,30% of her
total calories
(E) Decrease her caloric intake

Answer 15

The answer is C. Because her caloric intake (840 kcal/day) is less than her expenditure
(1,560 kcal/day), the woman is losing weight. She needs to increase her caloric intake. Exercise would cause her to lose more weight. She is probably in negative nitrogen balance because her protein intake is low (0.8 g/kg/day is recommended). Although her fat intake is 43% of her total calories and recommended levels are <30%, she should increase her total calories by increasing her carbohydrate and protein intake rather than decreasing her fat intake.

Question 16

Consider a normal 25-year-old man, about 70 kg in weight, who has been shipwrecked
on a desert island, with no food available, but plenty of freshwater. Which of the following fuel stores is least likely to provide significant calo- ries to the man?
(A) Adipose triacylglycerol
(B) Liver glycogen
(C) Muscle glycogen
(D) Muscle protein
(E) Adipose triacylglycerol and liver glycogen

Answer 16

The answer is B. As indicated in Table 1.1, in the average (70 kg) man, adipose tissue contains 15 kg of fat or 135,000 calories (kcal). Liver glycogen contains about 0.08 kg of carbohydrate (320 calories), and muscle glycogen contains about 0.15 kg of carbohydrate (600 calories). In addition, about 6 kg of muscle protein (24,000 calories) can be used as fuel. Therefore, liver glycogen contains the fewest available calories.

Question 17

The shipwrecked man described in the previous question will have most of his fuel stored as triacylglycerol instead of protein in muscle due to triacylglycerol stores containing which of the following as compared to protein stores?
(A) More calories and more water
(B) Less calories and less water
(C) Less calories and more water
(D) More calories and less water
(E) Equal calories and less water

Answer 17

The answer is D. Adipose tissue contains more calories (kilocalories) and less water than does muscle protein. Triacylglycerol stored in adipose tissue contains 9 kcal/g, and adipose tissue has about 15% water. Muscle protein contains 4 kcal/g and has about 80% water.

Question 18

A vegan has been eating low-quality vegetable protein for many years, and is now exhibiting a negative nitrogen balance. This may be occurring due to a lack of which one of the following in his/her diet?
(A) Linoleic acid
(B) Starch
(C) Serine
(D) Lysine
(E) Linolenic acid

Answer 18

The answer is D. A negative nitrogen balance will result from a diet deficient in one essential amino acid, or in a very diseased state. Linoleic and linolenic acids are the essential fatty acids in the diet, and a lack of these fatty acids will not affect nitrogen balance. Starch is a glucose polymer, and the lack of starch will not affect nitrogen balance. Lysine is an essential amino acid, whereas serine can be synthesized from a derivative of glucose. Lack of lysine in the diet will lead to a negative nitrogen balance as existing protein is degraded to provide lysine for new protein synthesis.

Question 19

A medical student has been studying for exams, and neglects to eat anything for 12 hours. At this point, the student opens a large bag of pretzels and eats every one of them in a short period. Which one of the following effects will this meal have on the student’s metabolic state?
(A) Liver glycogen stores will be replenished.
(B) The rate of gluconeogenesis will be
increased.
(C) The rate at which fatty acids are
converted to adipose triacylglycerols
will be reduced.
(D) Blood glucagon levels will increase.
(E) Glucose will be oxidized to lactate by
the brain and to CO2 and H2O by the red blood cells.

Answer 19

The answer is A. After a meal of carbohydrates (the major ingredient of pretzels), glycogen is stored in the liver and in muscle, and triacylglycerols are stored in adipose tissue. Owing to the rise in glucose level in the blood (from the carbohydrates in the pretzels), insulin is released from the pancreas and the level of glucagon in the blood decreases. Since blood glucose levels have increased, there is no longer a need for the liver to synthesize glucose, and gluconeogenesis decreases. The change in insulin-to-glucagon ratio also inhibits the breakdown of triacylglycerols and favors their synthesis. The brain oxidizes glucose to CO2 and H2O, whereas the red blood cells produce lactate from glucose, since red blood cells cannot carry out aerobic metabolism.

Question 20

After a stressful week of exams, a medical student sleeps for 15 hours, then rests in bed for an hour before getting up for the day. Under these conditions, which one of the following statements concern- ing the student’s metabolic state would be correct?
(A) Liver glycogen stores are completely depleted.
(B) Liver gluconeogenesis has not yet been activated.
(C) Muscle glycogen stores are contributing to the maintenance of blood glucose levels.
(D) Fatty acids are being released from adipose triacylglycerol stores.
(E) The liver is producing and oxidizing ketone bodies to CO2 and H2O.

Answer 20

The answer is D. During fasting, fatty acids are released from adipose tissue and oxidized by other cells. Liver glycogen is not depleted until about 30 hours of fasting. After an overnight fast, both glycogenolysis and gluconeogenesis by the liver help maintain blood glucose levels. Muscle glycogen stores are not used to maintain blood glucose levels. The liver produces ketone bodies but does not oxidize them, but under the conditions described in this question, ketone body formation would be minimal.

Question 21

A physician working in a refugee camp in Africa notices a fair number of children with emaciated arms and legs, yet a large protruding stomach and abdomen. An analysis of the children’s blood would show significantly reduced levels of which one of the following as compared with those in a healthy child?
(A) Glucose
(B) Ketone bodies
(C) Albumin
(D) Fatty acids
(E) Glycogen

Answer 21

The answer is C. The children are exhibiting the effects of kwashiorkor, a disorder resulting from adequate calorie intake but insufficient calories from protein. This results in the liver producing less serum albumin (due to the lack of essential amino acids), which affects the osmotic balance of the blood and the fluid in the interstitial spaces. Owing to the reduction in osmotic pressure of the blood, water leaves the blood and enters the interstitial spaces, producing edema in the children (which leads to the expanded abdomen). The children are degrading muscle protein to allow the synthesis of new protein (due to a lack of essential amino acids), and this leads to the wasting of the arms and legs of children with this disorder. The children will exhibit normal or slightly elevated levels of ketone bodies and fatty acids in the blood, as the diet is calorie sufficient. Glycogen levels may only be slightly reduced (since the diet is calorie sufficient), but glycogen is not found in the blood. Glucose levels will be only slightly reduced, as gluconeogenesis will keep glucose levels near normal.

Question 22

A 50-year-old male with a “pot belly” and a strong family history of heart attacks is going to his physician for advice on how to lose weight. He weighs 220 lb (100 kg) and is about 6’ tall (1.85 m). His lifestyle can be best described as sedentary.

What is this patient’s BMI?
(A) 24
(B) 29
(C) 31
(D) 36
(E) 40

Answer 22

The answer is B. The BMI is equal to kg/m2, which in this case is equal to 100/1.852, which is about 29.

Question 23

A 50-year-old male with a “pot belly” and a strong family history of heart attacks is going to his physician for advice on how to lose weight. He weighs 220 lb (100 kg) and is about 6’ tall (1.85 m). His lifestyle can be best described as sedentary.

Into which of the following categories does his BMI place him?
(A) Underweight
(B) Healthy
(C) Overweight (preobese)
(D) Obese (class I)
(E) Obese (class II)

Answer 23

The answer is C. The patient is in the overweight (preobese) category with a BMI of 29. As indicated in Table 1.2, a BMI of ,18.5 is the underweight category, a BMI between 18.5 and 24.9 is the healthy range, a BMI between 25 and 30 is the overweight (preobese) category, and any BMI of 30 or above is considered the obese range. Class I obese is between 30 and 35, whereas class II obese is between 35 and 40. Class III obesity, or morbidly obese, is the classification for individuals with a BMI of 40 or higher.

Question 24

A 50-year-old male with a “pot belly” and a strong family history of heart attacks is going to his physician for advice on how to lose weight. He weighs 220 lb (100 kg) and is about 6’ tall (1.85 m). His lifestyle can be best described as sedentary.

How many kilocalories per day would the patient need to maintain this weight?
(A) 2,400
(B) 2,620
(C) 3,120
(D) 3,620
(E) 3,950

Answer 24

The answer is C. The DEE is equal to the BMR plus physical activity factor. For the patient in question, the BMR 5 24 kcal/kg/day 3 100 kg, or 2,400 kcal/day. Since the patient is sedentary, the activity level is 30% that of the BMR, or 720 kcal/day. The overall daily needs are therefore 2,400 1 720 kcal/day, or 3,120 kcal/day. If the patient consumes ,3,000 kcal/day, or increases his physical activity level, then weight loss would result.

Question 25

A 50-year-old male with a “pot belly” and a strong family history of heart attacks is going to his physician for advice on how to lose weight. He weighs 220 lb (100 kg) and is about 6’ tall (1.85 m). His lifestyle can be best described as sedentary.

For which of the following disease processes is this patient at higher risk?
(A) Diabetes mellitus, type 1
(B) Insulin resistance syndrome
(C) Gaucher disease
(D) Low blood pressure
(E) Sickle cell disease

Answer 25

The answer is B. The patient’s weight, age, and activity put him at higher risk for insulin resistance syndrome. The entire syndrome includes hypertension, diabetes mellitus (type 2), decreased high-density lipoprotein levels, increased triglyceride levels, increased urate, increased levels of plasminogen activator inhibitor 1, nonalcoholic fatty liver, central obesity, and polycystic ovary syndrome (PCOS) (in females). Insulin resistance syndrome leads to early atherosclerosis throughout the entire body. The patient is not at increased risk for diabetes mellitus, type 1, as that is the result of an autoimmune condition that destroys the β cells of the pancreas such that insulin can no longer be produced. The lifestyle exhibited by the patient has not been linked to autoimmune disorders. Gaucher disease is a disorder of the enzyme β-glucocerebrosidase, and is an autosomal recessive disorder. Since this disease is an inherited disorder, the patient’s lifestyle does not increase his risk of having this disease. The patient’s increasing weight might lead to increased blood pressure, but not to reduced blood pressure. Sickle cell disease is another autosomal recessive disorder leading to an altered β-globin gene product, and like Gaucher disease, it is an inherited disorder that is not altered by the patient’s lifestyle.

Question 26

Which of the following metabolic patterns would be observed in a person after 1 week of starva- tion? Choose the one best answer.

Brain use of fuels /
Liver glycogen content (% of normal) /
Nitrogen balance /
Gluconeogenesis

(A) Glucose only / <5 / Positive / Inhibited
(B) Glucose and ketone bodies / <5 / Negative / Activated
(C) Ketone bodies only / <5 / Negative / Inhibited
(D) Fatty acids and ketone bodies / 50 / Positive / Activated
(E) Glucose and fatty acids / 50 / In balance / Inhibited

Answer 26

The answer is B. After 3 to 5 days of starvation, the brain begins to use ketone bodies, in addition to glucose, as a fuel source. Glycogen stores in the liver are depleted (,5% of normal) during the first 30 hours of fasting. Inadequate protein in the diet results in a negative nitrogen balance. Blood glucose levels are being maintained by gluconeogenesis, using lactate (from red blood cells), glycerol (from triacylglycerol), and amino acids (from the degradation of muscle proteins) as carbon sources.

Question 27

When compared with an individual’s state after an overnight fast, a person who fasts for 1 week will have which one of the following patterns expressed?

Blood glucose level / Amount of muscle protein / Amount of adipose triacylglycerol / Level of blood ketone bodies

(A) Higher / Greater / Greater / Lower
(B) Higher / Lower / Lower / Lower
(C) Lower / Greater / Greater / Greater
(D) Lower / Lower / Lower / Greater
(E) The same / The same / The same / The same

Answer 27

The answer is D. If a person who has fasted overnight continues to fast for 1 week, muscle protein will continue to decrease because it is being converted to blood glucose. However, it will not decrease at as rapid a rate as with a shorter fast, because the brain is using ketone bodies and, therefore, less glucose. The individual’s blood glucose levels will decrease about 40%, because initially glycogenolysis and then gluconeogenesis by the liver help to maintain blood glucose levels, but oxidation of ketone bodies by the brain will reduce the brain’s overall dependence on glucose. Adipose tissue will decrease as triacylglycerol is mobilized. Fatty acids from adipose tissue will be converted to ketone bodies in the liver. Blood ketone body levels will rise, and the brain will use ketone bodies as an alternative energy source, to reduce its dependency on glucose (during starvation, about 40% of the brain’s energy needs can be met by oxidizing ketone bodies, whereas the other 60% still requires glucose oxidation).

Question 28

Which one of the following is a common metabolic feature of patients with anorexia ner- vosa, untreated type 1 DM, hyperthyroidism, and nontropical sprue?
(A) A high BMR
(B) Elevated insulin levels in the blood
(C) Loss of weight
(D) Malabsorption of nutrients
(E) Low levels of ketone bodies in the blood

Answer 28

The answer is C. All of these patients will lose weight—the anorexic patients because of insufficient calories in the diet, the patients with type 1 DM because of low insulin levels that result in the excretion of glucose and ketone bodies in the urine, those with hyperthyroidism because of an increased BMR, and those with nontropical sprue because of decreased absorption of food from the gut. The untreated diabetic patients will have high ketone levels because of low insulin. Ketone levels may be elevated in anorexia and also in sprue, due to a reduction in levels of gluconeogenic precursors. An increased BMR would be observed only in hyperthyroidism. Nutrient malabsorption would occur only in nontropical sprue and anorexia.

Question 29

An 18-year-old person with type 1 diabetes has not injected her insulin for 2 days. Her blood glucose is currently 600 mg/dL (normal values are 80 to 100 mg/dL). Which one of the following cells of her body can still utilize the blood glucose as an energy source?
(A) Brain cells
(B) Muscle cells
(C) Adipose cells

Answer 29

The answer is A. Muscle and adipose cells require insulin to stimulate the transport of glucose into the cell, whereas the glucose transporters for the blood–brain barrier are always present,
and are not responsive to insulin. Thus, the brain can always utilize the glucose in circulation, whereas muscle and adipose tissue are dependent on insulin for glucose transport into the tissue.

Question 30

A patient is brought to the emergency room after being found by search and
rescue teams. He was mountain climbing,
got caught in a sudden snowstorm, and
had to survive in a cave. He had no food for
6 days. In adapting to these conditions, which metabolic process has increased rather than decreased?
(A) The brain’s use of glucose
(B) Muscle’s use of ketone bodies
(C) The red blood cells’ use of glucose
(D) The brain’s use of ketone bodies
(E) The red blood cells’ use of ketone bodies
(F) Muscle’s use of glucose

Answer 30

The answer is D. In the starvation state, muscle decreases the use of ketone bodies, causing an elevation of ketone bodies in the bloodstream. The brain uses the ketone bodies for energy and uses less glucose, which decreases the need for gluconeogenesis, thus sparing muscle protein degradation to provide the precursors for gluconeogenesis. Red blood cells cannot use ketone bodies and must utilize glucose. Therefore, the use of glucose by red blood cells would be unchanged under these conditions.

Question 31

A 27-year-old male got lost while hiking in Yo- semite National Park. He was found 8 days later. He had nothing to eat and only water to drink before being rescued.

Which one of the following would be his primary source of carbons for maintaining blood glucose levels when he was found?
(A) Liver glycogen
(B) Muscle glycogen
(C) Fatty acids
(D) Triacylglycerol
(E) Ketone bodies

Answer 31

The answer is D. The glycerol component of triacylglycerol would be the major contributor of carbons for gluconeogenesis among the answer choices provided. Substrates for hepatic gluconeogenesis are lactate (from red blood cells), amino acids (from muscle), and glycerol (from adipose tissue). Fatty acids would be used for energy, but the carbons of fatty acids cannot be used for the net synthesis of glucose. Hepatic glycogen stores are exhausted about 30 hours after the initiation of the fast, and muscle glycogen stores contribute only to muscle energy needs and not to the maintenance of blood glucose levels.

Question 32

A 27-year-old male got lost while hiking in Yo- semite National Park. He was found 8 days later. He had nothing to eat and only water to drink before being rescued.

Which cell can only use glucose for energy needs?
(A) Brain
(B) Red blood cells
(C) Hepatocyte
(D) Heart
(E) Muscle

Answer 32

The answer is B. Red blood cells lack mitochondria, so they can use only glucose for fuel (fatty acids and ketone bodies require mitochondrial proteins for their oxidative pathways). The brain can also use ketone bodies, along with glucose. The liver can use glucose, fatty acids, and amino acids as energy sources. The heart can use glucose, fatty acids, amino acids, and lactic acid as potential energy sources.

Question 33

A 27-year-old male got lost while hiking in Yo- semite National Park. He was found 8 days later. He had nothing to eat and only water to drink before being rescued.

Which one of the following is an essential nutrient that he has not received over the last 8 days?
(A) Lactic acid
(B) Oleic acid
(C) Steric acid
(D) EPA
(E) Palmitic acid

Answer 33

The answer is D. Eicosapentaenoic acid (EPA, a 20-carbon fatty acid containing five double bonds) can be derived from an essential fatty acid found in fish oils (linolenic acid), and is
a precursor of eicosanoids (prostaglandins, leukotrienes, and thromboxanes). EPA is also ingested from fish oils. Lactic acid is produced from muscle and red blood cells, and is not an essential nutrient. Palmitic acid (a fatty acid containing 16 carbons, with no double bonds), oleic acid (a fatty acid containing 18 carbons, with one double bond), and stearic acid (a fatty acid containing 18 carbons, with no double bonds) can all be synthesized by the mammalian liver through the normal pathway of fatty acid synthesis.

Question 34

A 27-year-old male got lost while hiking in Yo- semite National Park. He was found 8 days later. He had nothing to eat and only water to drink before being rescued.

The man’s brain would attempt to decrease consumption of glucose and increase consumption of ketones in order to protect the breakdown (catabolism) of which one of the following?
(A) Muscle glycogen
(B) Liver glycogen
(C) Muscle protein
(D) Red blood cells (to provide heme)
(E) Adipose triacylglycerol

Answer 34

The answer is C. In an attempt to save muscle tissue (amino acids used for gluconeogenesis), the brain in starvation mode will utilize ketone bodies for a portion of its energy needs. Liver glycogen stores would be depleted under the conditions described. Heme is not used for energy production, and produces bilirubin when degraded, which cannot be used to generate energy or ketone bodies. Muscle glycogen cannot contribute to blood glucose levels, as muscle tissue lacks the enzyme that allows free glucose to be produced within the muscle.

Question 35

A 27-year-old male got lost while hiking in Yo- semite National Park. He was found 8 days later. He had nothing to eat and only water to drink before being rescued.

Which one of the following lab tests should be run on the patient to determine whether he is suffering from overall protein malnutrition?
(A) Albumin
(B) Blood urea nitrogen (BUN)
(C) Creatinine
(D) Ferritin
(E) Creatine phosphokinase (CPK)

Answer 35

The answer is A. Albumin, though nonspecific, is considered the standard for assessing overall protein malnutrition. Albumin is made by the liver and is found in the blood. It acts as a nonspecific carrier of fatty acids and other hydrophobic molecules. When amino acid levels become limiting, the liver reduces its levels of protein synthesis, and a reduction in albumin levels in the circulation is an indication of liver dysfunction. Ferritin is an iron storage protein within tissues, and its circulating levels are low at all times. Creatinine is a degradation product of creatine phosphate (an energy storage molecule in muscle), and its presence in the circulation reflects the rate of creatinine clearance by the kidney. High levels of creatinine indicate a renal insufficiency. Creatine phosphokinase is a muscle enzyme that is released into circulation only when there is damage to the muscle. Blood urea nitrogen indicates the rate of amino acid metabolism to generate urea, but does not indicate protein malnutrition.