Chapter 7 Metabolism: Transformations and Interactionss3.amazonaws.com/prealliance_oneclass_sample/YzKXql3eYn.pdf · To teach metabolism well—that is, to teach it so that students

Enriched Instructor’s Manual to Accompany Understanding Nutrition, First Canadian Edition 7-1

Chapter 7Metabolism: Transformations and Interactions

I F N O T H I N G E L S E , M Y S T U D E N T S S H O U L D L E A R N …

1. How ingestion of the dietary macronutrients (i.e., carbohydrates, lipids, protein) are used by the cells of the human body. The macronutrients are used to serve a similar purpose (i.e., to make the highenergy compound adenosine triphosphate) but are metabolized by different processes.

2. How the ingestion of different amounts of the macronutrients will affect how the human body’s cells will metabolize them in order to resynthesize adenosine triphosphate.

3. How the human body metabolizes alcohol and how consumption will have a direct effect on health.

L E A R N I N G O B J E C T I V E S

Students should be able to:

• LO 7.1: Discuss the chemical reactions in the human body’s cells, and the difference between anabolism and catabolism. [Remember/Understand]

• LO. 7.2: Describe adenosine triphosphate and why this compound is important in the function of the human body. [Remember/Understand]

• LO 7.3: Explain how the human body handles dietary carbohydrates, in terms of storage and expenditure (i.e., glycogen synthesis, glycogenolysis, and glycolysis). [Remember/Understand]

• LO 7.4: Describe how the human body’s cells break down lipids (i.e., fatty acids) for purposes of supplying energy. [Understand/Apply]

• LO 7.5: Explain the process of deamination and the synthesis of nonessential amino acids. [Understand/Remember]

• LO 7.6: Discuss the metabolic relationship between the Kreb’s Cycle and the electron transport chain. [Remember/Understand]

Copyright © 2013 by Nelson Education Ltd.


• LO 7.7: Explain how feasting and fasting have different effects on the metabolism of the macronutrients in the human body’s cells. [Understand/Apply]

• LO 7.8: Describe how the human body metabolizes alcohol, the effects incurred on brain and liver cells, and the guidelines regarding alcohol consumption. [Understand/Apply]

W H Y I S T H I S C H A P T E R I M P O R T A N T T O S C I E N T I S T S A N D H E A L T H C A R E P R A C T I T I O N E R S ?

“Of special interest to...” symbol key:

= HealthCare Practitioners = Science Majors

• Scientists have long established the metabolic pathways that the body’s cells use to derive energy from macronutrients. Essentially, lipids, carbohydrates, and proteins serve as the fuel sources our cells use to resynthesize ATP in order to support numerous functions.

• Understanding how the human body handles carbohydrates, in terms of digestion, absorption, and metabolism will enable students to gain an appreciation of the importance of this macronutrient. The healthcare practitioner will gain an understanding of how the body reacts to different food sources of carbohydrates by appreciating the metabolic pathways in which cells use this macronutrient.

• The scientist will gain an appreciation of the intricate mechanisms involved in macronutrient metabolism by examining the interaction of various pathways (i.e., glycolysis, Kreb’s cycle, electron transport chain, etc.).

• The healthcare practitioner will learn about the body’s metabolic reaction to feasting (i.e., ingesting more energy than what is expended) or fasting (i.e., very low caloric intake). By understanding that the body will convert excessive macronutrients to fat when energy intake exceeds expenditure, or how the body catabolizes muscle tissue for energy during fasting, the healthcare practitioner will be able to make sound recommendations to patients regarding optimal nutritional strategies.

W H Y S H O U L D S T U D E N T S C A R E ?

• Students should be aware that some fad diets (for example, low carb diets) may likely cause changes to their metabolism that may result in the breakdown of muscle protein for energy. By gaining an appreciation of the complex metabolic pathways in which the body uses the macronutrients, students will understand why the basic premise in nutrition of practising adequacy, variety, and moderation



is sound.

• As many students begin living on their own when attending university, they very often pay little attention to their food that they’re eating and how it may affect their daily energy levels. By selecting convenient “fast food,” students may not be aware that their fat intake exceeds the recommended levels and will lead to deteriorations in their ability to maintain optimal health. By learning how the body metabolizes macronutrients, students will be able to make wellinformed choices in their diet.

• As the incidence of alcohol consumption by Canadian university students is very high, students should understand how the body metabolizes alcohol and how excessive intake is directly related to disease risk, as well as contributing to adverse behaviour due to the effects on the nervous system.

W H A T A R E C O M M O N S T U D E N T M I S C O N C E P T I O N S / S T U M B L I N G B L O C K S ?

1. The most significant challenge to students is keeping track of the complex interactions of the various metabolic pathways in which the body uses the macronutrients.

2. Students very often get caught up on trying to memorize the steps in each metabolic pathway without understanding the “big picture.” By focusing on the macronutrients, students will be able to draw a line from ATP production to the original fuel source from which it was derived.

3. Many students believe that since they do not drink every day, they are considered occasional drinkers, but they do not appreciate the dangers of binge drinking periodically. By focusing on how this chemical alters nervous system function, students will understand that excessive alcohol consumption is a detriment to optimal health.

W H A T C A N I D O I N C L A S S ?

There are a variety of activities that can be done in class. Listed below are some activities that will help introduce the topic of nutrition, and the students to each other.

To teach metabolism well—that is, to teach it so that students do not try to memorize fragments of it blindly but become intrigued with it, feel comfortable with it, and really understand it—is a challenge. It helps when you are enthused about the subject. It also helps to have your objectives clearly in mind, and not to be unrealistically ambitious. Do you want students to memorize and spit back all of the TCA cycle intermediates with their structures, or do you want them to be able to tell you in words what kinds of



transformations can occur among amino acids, fatty acids, and glucose? Offer as much as students are able to assimilate in the available time. It usually isn’t necessary to get into the details of the TCA cycle at the beginning level; too few gain any real understanding.

Classroom Activity 71: ChapterOpening QuizObjective: Introduction to chapter Class size: Any

Instructions: As a way of introducing any new chapter, give a quiz to the class. This is a quiz designed to be projected overhead. For details, please see Chapter 1, Classroom Activity 14.

Classroom Activity 72: Enhancing Understanding of Metabolism1

Key concept: Metabolism basics Class size: Any

Instructions: To explain human metabolism, an analogy based on the automobile can be offered. The oxidation of gasoline produces heat and energy (measured in kilometres per litre) and carbon dioxide and water are waste products. Nutrients and gasoline are both fuels that are oxidized in the presence of oxygen to produce energy, carbon dioxide, and water.

Ask students to consider a car having a manual transmission with only two gears: first and high. First gear is beneficial for rapid acceleration. If you do not shift out of first gear, the car will no longer accelerate, and it will use gasoline very inefficiently. You must shift into high gear to keep the car running efficiently at a higher speed. Human beings obtain energy from two analogous processes: glycolysis and the TCA cycle. Anaerobic glycolysis serves the need for quick energy to accomplish an intense activity for a short duration of time. For endurance activities, additional energy must be obtained from the TCA cycle. Explain that the choice of activity determines the proportion of fat and glucose burned during the activity.

1 Activity provided by Samantha Logan, DrPH, University of Massachusetts, Amherst.



Energy Obtained

Measure of Energy Advantage Disadvantage

Car First gear km/L Quick acceleration Can only be used for a few seconds of acceleration

Human beings

Glycolysis anaerobic

ATP Quick, intense muscle activity Can only be used for a few seconds as lactic acid is produced

Car High gear km/L Used to sustain desired velocity over maximum amount of time

Depends on rate of oxygen delivery to fuel source; better tuned engines achieve maximum km/L

Human beings

TCA cycle aerobic

ATP Used to sustain desired amount of muscle activity over maximum amount of time

Depends on rate of oxygen delivery to fuel source; better conditioning improves rate of oxygen delivery

Classroom Activity 73: Obtain Feedback Regarding Understanding of MetabolismObjective: Review and clarification Class size: Any

Instructions: Chapter 7 is one of the most challenging chapters in the textbook. Asking for feedback regarding the concepts that were grasped and others that were less understood can provide an excellent baseline regarding areas that need clarification for the subsequent class. At the end of class, students are asked to anonymously provide feedback on the day’s lesson. Students are asked to respond to two or three short questions that can vary in format and emphasis. Two common questions are: “What did you learn during this class?” and “What was least understood?”

In addition to providing valuable feedback for the instructor, it challenges students to evaluate their own learning.

Critical Thinking Questions2

These questions will also be posted to the book’s website so that students can complete them online and email their answers to you.

1. Describe the following: catabolism, anabolism, coupled reactions, enzyme/coenzyme, photosynthesis, and cofactor.

2. Discuss how the basic units of carbohydrate, protein, and lipid are utilized in energy pathways to produce energy. What are the differences and similarities?

3. If there were no external sources of energy available to the body, what would it do to produce energy? Discuss.

4. In a state of starvation, several changes happen within our bodies. Talk about these 2 Contributed by Kathleen Rourke.



metabolic changes and discuss the importance of interventions such as IV glucose and tube feedings for hospital patients that are severely sick and unable to eat.

5. Using information regarding the pathways (biochemistry), discuss why dietary plans that only stress one or a couple of food groups are unhealthy physiologically.

6. Many individuals enjoy a drink with friends or family during a special occasion and research does indicate that drinking alcoholic beverages in moderation does have some positive health benefits (in particular wine). However, alcohol consumption does have many negative consequences.

Discuss the differences between digestion and absorption of alcohol and that of other nutrients. Is alcohol a nutrient? As a registered dietitian, what are the areas that you must be mindful of in counselling patients?

W H A T O T H E R R E S O U R C E S A R E A V A I L A B L E ?

Consult the following websites to get reliable information on the following:

For information on basic physiological science, consult the American Physiological Society: http://www.theaps.org

For information regarding the influence of exercise and physical activity on human physiology and metabolism, refer to the following websites:

• Canadian Society for Exercise Physiology: http://www.csep.ca

• American College of Sports Medicine: http://www.acsm.org

Alcohol Use by Canadian University StudentsThe 2004 Canadian Campus Survey (CCS), funded by the Canadian Institutes of Health Research, surveyed alcohol use by Canadian University students. For the results from the CCS, go to the Centre for Addiction and Mental Health website: http://www.camh.net/research/population_life_course.html


http://www.camh.net/research/population_life_course.html

http://www.acsm.org/

http://www.csep.ca/

http://www.the-aps.org/


A N S W E R K E Y F O R A L L I N S T R U C T O R ’ S M A N U A L A C T I V I T I E S

Critical Thinking Questions3

These questions will also be posted to the book’s website so that students can complete them online and email their answers to you.

1. Answer: Catabolism: This is the breakdown of energyyielding compounds to provide energy for the body. For instance, the body can break down fat or it can use its own muscle tissue to provide energy to the body in times of starvation.

Anabolism: This is the building of compounds, such as glycogen and proteins. Anabolic reactions require energy.

Coupled Reactions: These are pairs of chemical reactions that assist one another. Energy released from one reaction can be used by the next reaction to complete the pair of reactions that would not exist independently.

Enzyme/Coenzyme: An enzyme is a protein that “catalyzes” or facilitates a chemical reaction. A coenzyme works with an enzyme and is an organic molecule. Many B vitamins are part of coenzyme structures.

Photosynthesis: The process carried out in plants that allows them to utilize the sun’s energy to make carbohydrates from carbon dioxide and water. In turn, by eating these plants, humans are also afforded energy.

Cofactor: These organic and inorganic substances also help to facilitate the work of enzymes. They include both vitamins and minerals.

2. Answer: Carbohydrates, fats, and proteins all enter energyproducing pathways, but their fates do differ slightly, depending on their role and chemical composition. For example, while carbohydrates and fats are energyyielding compounds, amino acids are really precursors to proteins and only a small percentage of their dietary consumption will be used for energy.

Carbohydrates: Carbohydrates yield energy through a series of reactions beginning with glycolysis. Here a sixcarbon glucose molecule is broken down into two threecarbon molecules that are converted to pyruvate. Anaerobically, pyruvate can be converted to lactate, allowing for a small amount of energy under anaerobic conditions, or the pyruvate can be broken down to acetylCoA under aerobic conditions in the TCA cycle. Conditions that allow pyruvate to move on through the TCA cycle into the electron transport chain will optimize the energy released from the initial glucose molecule

Lipids: Triglycerides compounds are composed of two components, glycerol and fatty acids. Glycerol is a threecarbon compound and, as such, is able to enter glycolysis, either for gluconeogensis or for glycolysis (breakdown of glucose). From

3 Contributed by Kathleen Rourke.



there, glycerol is broken down to pryuvate and continues on into the TCA cycle, producing energy via the electron transport system. Because there is only one glycerol unit for every three fatty acids, the number of glycerol compounds entering glycolysis is significantly less.

Given that fatty acids are split into twocarbon compounds, they cannot enter the energy system until the point of acetylCoA. It is important to remember that because fatty acids enter at the point of acetylCoA, they are not capable of producing glucose.

What is important to note here is that lipids do supply a source of energy from two different vantage points. While they enter the energy system at a different point from that of carbohydrates, there are some points in common. Secondarily, glycerol functions far differently than do the fatty acids. While glycerol can produce some glucose, its capability is limited given its scarcity relative to fatty acids.

Amino Acids: The amino acids that make up proteins are very capable characters. They are able to enter the energy pathway at several points. However, prior to serving in any capacity in the energy pathways, they must be deaminated, which is the process in which their amine group is removed, thus removing the ammoniaproducing unit. Amino acids can serve as a compound to make glucose through glycolysis and in the TCA cycle. Amino acids (nonessential) are distinguished by their ability to make glucose or ketones. Glucogenic amino acids enter glycolysis at the level of pyruvate as threecarbon compounds. They can be used to make pyruvate and then be used in gluconeogenesis to make glucose. Ketogenic amino acids are used to make acetylCoA. Other glucogenic amino acids can enter the TCA cycle as fourcarbon compounds and serve as an energy source or be stored as fat.

Amino acids are capable of producing glucose or ketones (in the absence of glucose) in the event of need for the body. The amino acid’s points of entry into the energy system are several and this demonstrates its vital purpose to our bodies. It must be remembered that the primary function of amino acids is tissue building and repair; therefore, this role in energy production is secondary to that of tissue maintenance.

3. Answer: If macronutrients are not available via ingested food, the body can rely on its stores of energyyielding compounds to survive, often for an extended period. Glycogenolysis in the liver breaks down glycogen stores, and glucose is released into the blood; adipose tissues release fatty acids and glycerol into the blood as well. Because some cells prefer or can only metabolize glucose for energy, gluconeogenesis accelerates once liver glycogen is exhausted. The substrates for gluconeogenesis include glucogenic amino acids from degraded muscle tissues, so some muscle wasting will occur during a lengthy fast. This wasting is limited, however, by the acceleration of the formation of ketones—another energyyielding compound that can be metabolized by certain cells, including those of the brain—from lipid and amino acid fragments. (The fatty acid fragments result from incomplete fat metabolism caused by the glucose shortage.)



4. Answer: In a state of starvation, the body continues to require energy to perform all of its functions. As noted many times throughout your textbook thus far, the brain is only able to utilize glucose or ketones, as is the majority of the nervous system. Even while an individual is asleep, the body continues to carry out thousands of metabolic reactions that require energy; thus, we calculate the basal metabolic rate, which is a significant part of any individual’s daily caloric requirements, for each patient. Therefore, nutrients are needed for the body to function while sleeping. Added to that, a patient in a hospital setting has a body that is trying to heal from a trauma or disease. It must also be kept in mind that a hospital setting adds its own set of stress factors—environmentally, physically, etc. For the most part, hospital patients require added nutrients to heal and protect their bodies from the many hospital stress factors.

Supplemental nutrients via an IV, tube feedings, etc. have been shown to decrease hospital stays for surgical patients. Something as simple as an IV with dextrose will provide the patient with added glucose for brain and nervous system function. While the calories are minimal, at best, it helps to prevent the patient from breaking down their own body tissues (ketosis) to support brain function, etc. The hydration is also important, particularly in the very young and the very old.

Patients with longer stays should have recommended tube feedings or parentrel feedings to support the body functions for the increased periods of time. Such feedings can provide needed vitamins and minerals that may be easily lost in critical illness.

Careful attention to patient hydration and supplemental feedings can save lives as well as avoid costly hospital stays. Nutrition can help to prevent skin breakdown, reverse dehydration, improve healing time, and brighten the overall outlook of the patient.

5. Answer: After reading this chapter, students should be able to see the importance of not only all the macronutrient groups but also the vitamins and minerals that assist as cofactors in many metabolic reactions. All of the food groups work together to ensure that our bodies are properly nourished.

As noted, carbohydrates provide the body with an importance source of energy: glucose. Most particularly, the brain and nervous system benefit from this glucose, but the entire body benefits from the fibre, vitamins, and minerals received when an individual selects wholegrain carbohydrates. Selecting a diet that is void in carbohydrates forces the body to use proteins as an energy source and can deny the body vital amino acids for use in tissue building and repair under traumatic or stressful situations. This differential function between carbohydrates and protein is important to educate patients about when providing nutrition counselling.

Proteins are made up of the important building blocks called amino acids. Some of these are essential, meaning that they cannot be made by the body, and many are nonessential because the body can make them on its own. Selecting a diet with a variety of protein sources provides for the essential amino acids and ensures that the body has the building blocks it needs for tissue building, repair, etc. Production of glucose should be considered a secondary function for amino acids.



While many individuals love foods drenched in butter, etc., dietary lipids need not be so abundant. Yet lipids are vital to a healthy body for production of steroid hormones and cell membranes, just to name a few important roles for lipids. In addition, a small amount of fat within the body is necessary to protect vital organs and to provide insulation from the cold. That being said, no more than two to three tablespoons a day of added lipid is necessary in our diets. As noted, glycerol can provide a limited source of glucose when necessary and fatty acids are broken down to acetylCoA as required for energy production. Otherwise, excess fatty acid consumption is easily converted to and stored as fat in the body.

Without all of these macronutrients working together, our bodies would require one (such as proteins) to replace the function of another (such as carbohydrates). In these events, not only are their “normal” jobs disturbed, but the other nutrients, such as vitamins and minerals, that may accompany a food group are also denied to the body. It is not the food group itself that causes an individual weight problems; it is the quantity of the food group that generally becomes the issue.

6. Answer: Alcohol is not a nutrient and is not treated as a nutrient by the body. It can be very toxic to the body; therefore, the body works quickly to excrete it. As such, alcohol is not digested but quickly absorbed in the stomach and small intestine. If consumed with food, its absorption in the stomach will be disrupted. Alcohol not absorbed in the stomach is broken down by alcohol dehydrogenase, an enzyme secreted into the stomach, or absorbed from the small intestine. All absorbed alcohol is carried from the blood to the liver to be metabolized and the toxins are excreted.

Because of the nature of alcohol, processes that normally take place are put on hold until all alcohol is metabolized by the body. For example, in the liver, fatty acids that are generally preferentially packaged for storage become stored in the liver until all the body’s alcohol has been metabolized. Electrons that are being used for other metabolic processes are now captive as the completion of alcohol metabolism takes place.

In the brain, alcohol acts as an anesthetic; however, alcohol’s effects are inconsistent across each individual’s body, depending on size (weight), gender, genetics, etc. The effect of alcohol on judgment, speech, and overall motor function is quite variable and can be deadly if one becomes over intoxicated.

Finally, alcohol is accompanied by calories and excessive calories are stored as fat by the body. In addition, many mixed drinks include many additional calories. The best advice for patient is that if they choose to drink alcohol, they should do so in moderation. The registered dietitian should advise people never to drink on an empty stomach and never to mix other drugs and alcohol. Remind your patients that alcohol can be extremely toxic to the body and it requires its on priority system for clearance. A glass of wine with friends can be a healthy social event when combined with food and conversation. Know your body and its limits and enjoy family and friends first.



Worksheet Answer KeyWorksheet 71: Metabolism Exercises1. Anabolic

2. Catabolic

3. Catabolic

4. Anabolic

5. Catabolic

6. Anabolic

7. Catabolic

8. Catabolic

9. Catabolic

10. Anabolic

11. Anabolic

12. Catabolic

13. Catabolic

14. Anabolic

15. Catabolic

Worksheet 72: Blood Alcohol Levels 1.–3. Answers will vary based on the individual’s weight.4. Gender, tolerance of alcohol, other drugs used, amount of food present in the

GI tract, certain medical conditions, etc.

Worksheet 73: Anabolic or Catabolic?1. Catabolic

2. Anabolic

3. Anabolic

4. Catabolic

5. Catabolic

6. Anabolic

7. Catabolic

8. Anabolic

9. Catabolic

Worksheet 74: Chapter 7 Crossword Puzzle1. aerobic

2. coenzymes

3. catabolism

4. transamination

5. glycolysis

6. fuel

7. urea

8. anabolism

9. metabolism

10. anaerobic



W O R K S H E E T A C T I V I T I E S

Worksheet 71: Metabolism Exercises

Indicate whether each of the following reactions is anabolic or catabolic by circling the appropriate word:

Reaction Type of Reaction

1. Glucose + glucose glycogen → Anabolic Catabolic

2. C6H12O6 + 6H2O 6CO→ 2 + 6H2O Anabolic Catabolic

3. AB A + B → Anabolic Catabolic

4. Glycerol + fatty acids lipids → Anabolic Catabolic

5. Glycolysis Anabolic Catabolic

6. Glucose molecules linked to form glycogen Anabolic Catabolic

7. Electron transport chain Anabolic Catabolic

8. Oxidation reaction Anabolic Catabolic

9. Muscle tissue breakdown release of amino acids → Anabolic Catabolic

10. Adipose tissue formed from fatty acids Anabolic Catabolic

11. AOH + HB AB + HOH → Anabolic Catabolic

12. AB + HOH AOH + HB → Anabolic Catabolic

13. Beta oxidation of fatty acids Anabolic Catabolic

14. Gluconeogenesis Anabolic Catabolic

15. NADH + H2 NAD→ + Anabolic Catabolic



Worksheet 72: Blood Alcohol Levels

Go to an automatic calculator on the Internet by accessing http://www.ou.edu/oupd/bac.htm. Estimate your potential blood alcohol concentration after a number of drinks.

Use the calculator to complete the table below based on your weight (choose the weight closest to yours from the list). Select one type of drink from the list on the website, and use that same type of drink for each calculation. If you drink, choose the beverage you like best or consume most often. Use three hours as the time period. Pay attention to the description of your theoretical state (e.g., “possible impairment”) as well as your blood alcohol levels.

Type of drink selected: _____________________________________________

Number of Drinks

Blood Alcohol Concentration

1

2

3

4

5

6

7

8

Reflect on this information, and answer the following questions.

1. What did the website predict your state of alertness would be after four drinks? After six? After eight?

2. After how many drinks did it predict your BAC would reach or exceed the legal limit for driving, 0.08%?

3. Calculate your expected BAC using this same number of drinks for two other types of alcoholic beverages. List the beverages you tried, and state how this affected the BAC.

4. What other factors besides those used by the calculator can affect BAC after a given alcohol intake?


http://www.ou.edu/oupd/bac.htm


Worksheet 73: Anabolic or Catabolic?

Metabolism explains how the cells in the body use nutrients to meet its needs. Cells may start with small, simple compounds and use them as building blocks to form larger, more complex structures (anabolism). These anabolic reactions involve doing work and so require energy. Alternatively, cells may break down large compounds into smaller ones (catabolism). Catabolic reactions usually release energy. Determine whether the following reactions are anabolic or catabolic.

Anabolic Catabolic

1. A cracker becomes glucose.

2. Glucose becomes glycogen.

3. You consume more energy than your body expends.

4. Fasting.

5. A piece of ham becomes amino acids.

6. Amino acids become your muscles.

7. A cookie becomes fatty acids.

8. Fatty acids become body fat.

9. Fatty acids provide energy.



Worksheet 74: Chapter 7 Crossword Puzzle

Across Down

1. Requiring oxygen6. Compounds that cells can use for energy8. Reactions requiring energy in which

small molecules are put together to build larger ones

9. The sum total of all the chemical reactions that go on in living cells

10. Not requiring oxygen

2. Small organic molecules that work with enzymes to facilitate the enzymes’ activity

3. Reactions in which large molecules are broken down to smaller ones

4. The transfer of an amino group from one amino acid to a keto acid, producing a new nonessential amino acid and new keto acid

5. The metabolic breakdown of glucose to pyruvate

7. The principal nitrogenexcretion product of metabolism


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Documents

Chapter 7 Metabolism: Transformations and Interactionss3.amazonaws.com/prealliance_oneclass_sample/YzKXql3eYn.pdf · To teach metabolism well—that is, to teach it so that students