Energy Metabolism Test Bank Answers Ch4

Chapter 4

Energy Metabolism

Learning Objectives

Upon successful completion of this chapter, students should be able to:

1. Explain the roles of carbohydrates, lipids, and protein in energy metabolism.
2. Discuss how the respiratory quotient helps us understand nutrient oxidation.
3. Define basal and resting metabolic rate, and describe factors that influence metabolic rate and how these factors relate to weight management.
4. Define adaptive thermogenesis and diet-induced thermogenesis, and describe factors that influence thermogenesis and how these factors relate to weight management.
5. Define activity energy expenditure and non-exercise activity thermogenesis, and describe factors that influence activity energy expenditure.
6. Apply the energy balance equation to weight gain, weight loss, and weight maintenance.

Chapter Outline/Summary

I. Energy balance equation tells us that energy intake = energy expenditure +/- energy (fat) storage. While the kcal value of fat (3,500 kcal per one pound of stored fat) seems like this equation is predictable, it is not quite that simple. Reducing “energy in” has an effect on “energy out.”

II. Energy in: the metabolic fate of ingested food

A. How food energy is transformed:

Carbohydrates, lipids, and protein (the energy nutrients) provide the energy for metabolism and activity. Before their energy can be used, a compound called adenosine triphosphate (ATP) must be formed. This occurs as the energy nutrients proceed through anaerobic (carbohydrates only) or aerobic (all energy nutrients) processes – glycolysis, the citric acid cycle, and electron transport and oxidative phosphorylation.

B. Role of carbohydrates in energy metabolism:

Carbohydrates are initially broken down through glycolysis, which may be anaerobic (the end product being lactic acid) or aerobic (the end product being pyruvate). Pyruvate enters the citric acid cycle by joining with acetyl coenzyme A, which forms oxaloacetate and then citrate, proceeding through a series of reactions that result in hydrogen carriers moving electrons to the inner membrane of the mitochondria where ATP is synthesized through oxidative phosphorylation.

C. Role of lipids in energy metabolism:

Lipids are a vast source of potential energy. Before they can enter the citric acid cycle, lipids must undergo beta oxidation, in which pairs of carbon atoms are successively removed from their lengthy carbon chains. As with carbohydrates, as lipids proceed through the citric acid cycle, hydrogen carriers move electrons to the inner membrane of the mitochondria where ATP is synthesized through oxidative phosphorylation. Sufficient carbohydrate is required for the citric acid cycle to operate efficiently. Without carbohydrate excess lipids are converted to ketones that may build up in the tissues.

D. Role of protein in energy metabolism:

Energy metabolism should never be the primary function of proteins, although amino acids can enter the same aerobic metabolic pathways as lipids and carbohydrates.

E. How we know which nutrient is used for fuel:

The volume of carbon dioxide produced for every unit of oxygen consumed allows us to calculate the respiratory quotient (RQ), a value that reflects the relative contribution of carbohydrate, fat, and protein to energy expenditure. The caloric value of oxygen consumed varies at different RQs, so individuals doing the same activity, but metabolizing different proportions of energy nutrients, may be expending different amounts of energy.

F. Dietary fats as key regulators of energy balance:

For body weight to remain stable, nutrients burned to sustain metabolism must be oxidized in proportion to their presence in the diet. Carbohydrates and protein tend to be oxidized in proportion to their presence in the diet. Fat oxidation is not as tightly regulated. An individual consuming a high-fat diet must burn that fat for energy, or the excess will be stored. Exercise can increase fat oxidation.

III. Energy expenditure: metabolic rate

1. Determination of RMR:

Metabolic rate is most accurately obtained by direct calorimetry (heat production). This method is reserved for the research laboratory. Indirect calorimetry – measurement of oxygen consumed and carbon dioxide produced – is a more practical method of estimating heat production. RMR can also be estimated with mathematical equations.

1. Factors that affect RMR:

Body size is the most important factor governing RMR. Other factors include: age, muscle mass, thyroid hormone levels, nutritional status (fasting or low caloric intake lowers RMR), genetics, and race.

1. Exercise and RMR:

After we exercise, we continue to expend energy due to excess postexercise oxygen consumption (EPOC). Some people may experience an increase in RMR following regular exercise, but the research on this is not yet conclusive.

1. RMR and obesity:

Because of their larger body size, overweight/obese individuals have higher RMRs than non-obese/overweight. Some obese individuals have lower RMRs than expected. Repeated dieting may be one factor responsible for this.

IV. Energy expenditure: adaptive thermogenesis

1. Mechanism for adaptive thermogenesis:

Adaptive thermogenesis is the production of heat after exposure to the cold or after eating. Diet-induced thermogenesis (DIT) is the component of adaptive thermogenesis that occurs after eating. Brown adipose tissue (BAT) is responsible for this. Some animals and humans have smaller amounts of, or less active, BAT which may contribute to obesity.

1. Defective thermogenesis and obesity:

Eating more frequent, smaller meals, a diet rich in carbohydrates, and certain foods can increase DIT. About half of studies have found defective DIT in obesity.

V. Activity energy expenditure

1. Measurement:

All of the activity that occurs when we are not at rest constitutes activity energy expenditure. The cost of physical activity is greater among people with larger body sizes. Heart rate is a good indicator of caloric expenditure, because there is an approximately linear relationship between heart rate and oxygen consumption.

1. Relationship to weight:

Activity energy expenditure is the component of energy out that makes the most difference in calories out between people. Non-exercise activity thermogenesis (NEAT) – fidgeting, activities of daily living, standing, climbing stairs, random muscle movements – has the potential to increase daily energy expenditure and help people lose or maintain weight. NEAT decreases when people consume too few calories. The physical activity index (PAI), calculated by dividing total daily energy expenditure by RMR, helps explain how much activity is needed to allow weight loss or weight maintenance.

VI. Conclusions about energy metabolism

Most people attribute weight gain to excess caloric intake. But weight gain also occurs when energy expenditure is insufficient.

Suggested Activities and Applications

Application 4.1 Resting Metabolic Rate

Students will pick two appropriate formulas from Table 4-4 and calculate their RMR. They will comment on factors not reflected in the formulas that might make their actual RMR lower or higher. For example, while formulas take into account gender, age, and body size, formulas cannot account for thyroid hormone, nutritional status, race, and genetics.

Application 4.2 Diet-Induced Thermogenesis

Students will summarize their personal eating habits, number of meals per day, frequency of snacking, timing of meals and snacks, size of typical meals, and types of foods consumed. Based on this, they will make some assumptions about aspects of their diet that might affect energy expenditure. For example, research suggests that frequency of eating, type of nutrients consumed, and specific foods (caffeine, hot peppers) may influence diet-induced thermogenesis.

Application 4.3 NEAT

Students are asked to ponder their own non-exercise energy expenditure (NEAT). They should think about how active they typically are in the course of a few typical days – if they have a job, what does it require in terms of physical exertion? Do they stand a lot? Does their leisure consist of seated activities, or activities that require some movement? How many labor-saving devices do they typically use? Do they commute by car or by subway? Then students can brainstorm, perhaps in groups, some ways to increase NEAT.

Test Bank Ch. 4

True/False

1. BMR accounts for 65-75% of total energy output.

2. The terms calorie (with a small c) and kilocalorie are often used interchangeably.

3. People usually use one energy nutrient at a time to fuel their activities.

4. The caloric value of oxygen varies depending on whether carbohydrate or fat is the primary fuel being used.

5. Obesity can develop from a failure to balance fat intake with fat oxidation.

6. After you eat, most dietary carbohydrate is either used for cellular functions or converted to glycogen for storage in the liver and muscles.

7. Some experts have estimated that an intake of 2,000-2,500 kcal of carbohydrate over several days, after carbohydrate stores were at maximum, would be required before carbohydrate would be converted to fat.

8. Fat stores are limited in size.

9. Replacing dietary carbohydrates with fat promotes obesity.

10. A diet that is high in fat and low in carbohydrate reduces the size of glycogen stores and stimulates hunger.

11. Fats in your diet are more satiating than carbohydrates and are more likely than carbohydrates to turn off appetite.

12. People who regularly consume a high-fat diet tend to eat more.

13. When carbohydrate stores run low, fat oxidation slows.

14. All fats have the same metabolic effects.

15. Most people who expend more energy in exercise and physical activity oxidize more fat.

16. High intensity exercise has been shown to oxidize a higher proportion of calories from fat.

Multiple Choice

17. Which of the following is NOT one of the three principle components of daily total energy expenditure (TEE):

A. Basal/Resting Metabolic Rate (BMR or RMR)

B. Adaptive Thermogenesis

C. Active Energy Expenditure

D. Energy Nutrients

18. How much adaptive thermogenesis is accounted for in daily energy output?

A. 10-15%

B. 15-25%

C. 25-30%

D. 30-40%

19. Which of the three components of daily total energy expenditure (TEE) has the greatest potential for increased TEE and possible weight loss?

A. Basal/Resting Metabolic Rate

B. Adaptive Thermogenesis

C. Activity energy Expenditure

D. All of the above

20. Generally, energy expenditure equal to _____kcal will result in a loss of 1lb.

A. 1,500 kcal

B. 2,500 kcal

C. 3,500 kcal

D. 4,000 kcal

21. This compound is made up of adenine (a carbon-nitrogen substance), ribose (a sugar), and three inorganic phosphates and stores chemical energy from food in high-energy bonds between the phosphates.

A. Adenosine triphosphate (ATP)

B. Glycolysis

C. Monosaccharide

D. Amino acid

22. __________________________ is the sum of all the energy transformation process in the human body.

A. Glycolysis

B. Metabolism

C. Electron transport

D. Oxidative phosphorylation

23. This metabolic process takes place in the cytoplasm, or fluid portion, of each cell and does not require/ use oxygen.

A. Anaerobic metabolic process

B. Aerobic metabolic process

C. Ketosis

D. Resting Metabolic Rate

24. This metabolic process occurs in the cell mitochondria and requires oxygen.

A. Anaerobic metabolic process

B. Aerobic metabolic process

C. Resting Metabolic Rate

D. Adaptive Thermogenesis

25. ___________________________ are required to burn fats.

A. Carbohydrates

B. Proteins

C. Both carbohydrates and proteins are required to burn fats

D. Fats

26. ________________________ is a metabolic process that may occur anaerobically or aerobically, in which glucose or glycogen is broken down to pyruvate (aerobic) or lactate (anaerobic) and APT is produced.

A. Oxidative phosphorylation

B. Glycolysis

C. Citric Acid Cycle

D. All of the above

27._____________________________ cannot continue indefinitely, in part because the production of lactic acid inhibits a key enzyme (phosphofructokinase) and ultimately slows down metabolism.

A. Aerobic glycolysis

B. Anaerobic glycolysis

C. Oxidative phosphorylation

D. All of the above

28.________________________ is the aerobic metabolic process that fully breaks down carbohydrate, fat, or protein to generate ATP, from carbon dioxide and water, and removes hydrogen atoms for the electron transport system.

29. _________________________ is the final stage of aerobic energy metabolism, in which ATP is synthesized from the energy generated in the electron transport system.

A. Aerobic glycolysis

B. Oxidative phosphorylation

C. Glycolysis

D. All of the above

30. ___________________________ is the aerobic process involving the removal of pairs of carbon atoms from fatty acids to allow fats to enter the citric acid cycle.

A. Ketosis

B. Glycolysis

C. Beta Oxidation

D. All of the above

31. _________________________ is the buildup of ketone bodies in body tissue resulting from incomplete oxidation of fats.

A. Ketosis

B. Beta oxidation

C. Citric acid cycle

D. Diet induced thermogenesis

32. In the average adult, about _____% of total stored energy is in the form of protein.

A. 10%

B. 25%

C. 30%

D. 40%

33. __________________________ is an indicator of the proportion of carbohydrate, fat, and protein being used to produce energy; this is calculated by dividing liters of carbon dioxide produced by liters of oxygen consumed.

A. Energy nutrients

B. Beta oxidation

C. Respiratory quotient

D. Adaptive thermogenesis

34. __________________________ are fats mainly found in animal products, such as butter, cheese and beef.

A. Polyunsaturated fats

B. Saturated fats

C. Monounsaturated fats

D. All of the above

35. _______________________ are fats mainly found in plant products, such as safflower oil and corn oil.

A. Polyunsaturated fats

B. Saturated fats

C. Monounsaturated fats

D. All of the above

36. _____________________ are fats that are also found in plant fats. These fats are found predominantly in nuts, olive oil, and canola oil.

A. Polyunsaturated fats

B. Saturated fats

C. Monounsaturated fats

D. All of the above

37. _______________________ is the measurement of heat generated as a result of metabolism and is the most accurate technique for measuring resting energy expenditure.

A. Direct calorimetry

B. Indirect calorimetry

C. Kilocalorie

D. All of the above

38. _______________________ is heat production that follows exposure to the cold or food intake.

A. Excess postexercise oxygen consumption

B. Adaptive thermogenesis

C. Diet induced thermogenesis

D. B& C

39. Which of the following describes the process of thermogenesis?

A. burning of fat

B. synthesis of fat

C. generation of heat

D. generation of water

40. Which of the following nutrients is oxidized at a higher rate when its intake is increased?

A. Fat

B. Carbohydrate

C. Protein

D. A and B

E. B and C

41. If muscle work is anaerobic, which of the following cannot serve as fuel?

A. fat

B. protein

C. carbohydrate

42. What fraction of the day’s energy expenditure of the average person is represented by the basal metabolism?

A. about 1/10

B. up to ½

C. about 2/3

D. over 9/10

Fill in the Blank/Short Answer

43. _________________ are the nutrients (carbohydrate, fat, and protein) that contain calories.

44. ______________________ is the measure of the energy value of food; technically, the amount of heat required to raise the temperature of 1kg of water 33.8°F (1°C).

45. Describe the difference between slow-twitch (type I) muscle fibers and fast-twitch (type II) muscle fibers.

46. ______________________ represents the sum of oxygen consumption of the active tissues of the body when an individual is resting but not asleep.

47. Describe three factors that influence RMR.

48. Describe NEAT. Why is NEAT important when considering weight loss strategies?

49. What are the major differences between aerobic and anaerobic metabolism? What types of activities are aerobic? Anaerobic?

50. What is the significance of the RQ?

51. Why might the components of energy out be even more important than food intake in explaining difficulties some people have in losing weight?

52. Describe the concept of diet-induced thermogenesis. Why is thermogenesis important factor for weight management professionals to consider?