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Chapter 7-1 Chapter 7 – Energy Metabolism Learning Objectives After completing Chapter 7, the student will be able to: 7.1 7.2 7.3 H7 Identify the nutrients involved in energy metabolism and the high-energy compound that captures the energy released during their breakdown. a. Discuss the chemical reactions that occur within the body, including metabolism, anabolism, and catabolism. Summarize the main steps in the energy metabolism of glucose, glycerol, fatty acids, and amino acids. a. Describe how carbohydrates, proteins, and fats are used to meet the energy needs of the body. b. Explain the process of glycolysis. c. Explain the process of deamination and the synthesis of non-essential amino acids. d. Discuss the TCA cycle and the electron transport chain. Explain how an excess of any of the three energy-yielding nutrients contributes to body fat and how an inadequate intake of any of them shifts metabolism. Describe how alcohol disrupts metabolism and impairs health. a. Discuss the term moderation in reference to alcohol consumption. b. Explain how the body metabolizes alcohol. c. Discuss the role of the liver in alcohol metabolism. d. Discuss the short- and long-term effects of alcohol on health. Assignments and Other Instructional Materials The following ready-to-use assignments are available in this chapter of the instructor’s manual: New! Case Study 7: Excessive Alcohol Use Worksheet 7-1: Metabolism Exercises1 Worksheet 7-2: Anabolic or Catabolic?2 Updated! Worksheet 7-3: Fat and Carbohydrate Metabolism (Internet Exercise) Worksheet 7-4: Blood Alcohol Levels Worksheet 7-5: Chapter 7 Crossword Puzzle3 Critical thinking questions with answers New! Key Terms and Definitions Other instructional materials in this chapter of the instructor’s manual include: Answer key for study card questions Classroom activities Worksheet answer keys (as appropriate) Handout 7-1: The Carbons of a Typical Triglyceride Visit the book’s instructor companion website to download: Handout 7-2: Alcohol’s Effects on Nutrients in the Body 1 Worksheets 7-1 and 7-3 contributed by Daryle Wane. Worksheet 7-2 and Handout 7-1 contributed by Sharon Rady Rolfes 3 Contributed by Carrie King. 2 © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-2 Glossary Chapter Key Terms acetyl CoA (ASS-eh-teel or ah-SEET-il, coh-AY): a 2-carbon compound (acetate or acetic acid) to which a molecule of CoA is attached. aerobic (air-ROE-bic): requiring oxygen. anabolism (an-AB-o-lism): reactions in which small molecules are put together to build larger ones. Anabolic reactions require energy. o ana = (build) up anaerobic (AN-air-ROE-bic): not requiring oxygen. o an = not ATP, or adenosine (ah-DEN-oh-seen) triphosphate (try-FOS-fate): a common high-energy compound composed of a purine (adenine), a sugar (ribose), and three phosphate groups. ATP 5 A–P~P~P, with each ~ denoting a “high-energy” bond. catabolism (ca-TAB-o-lism): reactions in which large molecules are broken down to smaller ones. Catabolic reactions release energy. o kata = (break) down CoA (coh-AY): coenzyme A; the coenzyme derived from the B vitamin pantothenic acid and central to energy metabolism. coenzymes: complex organic molecules that work with enzymes to facilitate the enzymes’ activity. Many coenzymes have B vitamins as part of their structures. o co = with Cori cycle: the pathway in which glucose is metabolized to lactate (by anaerobic glycolysis) in the muscle, lactate is converted back to glucose in the liver, and then glucose is returned to the muscle; named after the scientist who elucidated this pathway. coupled reactions: pairs of chemical reactions in which some of the energy released from the breakdown of one compound is used to create a bond in the formation of another compound. electron transport chain: the final pathway in energy metabolism that transports electrons from hydrogen to oxygen and captures the energy released in the bonds of ATP; also called the respiratory chain. enzymes: proteins that facilitate chemical reactions without being changed in the process; protein catalysts. fatty acid oxidation: the metabolic breakdown of fatty acids to acetyl CoA; also called beta oxidation. fuel: compounds that cells can use for energy. The major fuels include glucose, fatty acids, and amino acids; other fuels include ketone bodies, lactate, glycerol, and alcohol. gluconeogenesis (gloo-ko-nee-oh-JEN-ih-sis): the making of glucose from a noncarbohydrate source such as amino acids or glycerol. o gluco = glucose glycolysis (gly-COLL-ih-sis): the metabolic breakdown of glucose to pyruvate. Glycolysis does not require oxygen (anaerobic). o glyco = glucose o lysis = breakdown keto (KEY-toe) acid: an organic acid that contains a carbonyl group (C5O). ketone (KEE-tone) bodies: acidic compounds produced by the liver during the incomplete breakdown of fat when is not available carbohydrate. lactate: a 3-carbon compound produced from pyruvate during anaerobic metabolism. metabolism: the sum total of all the chemical reactions that go on in living cells. Energy metabolism includes all the reactions by which the body obtains and expends the energy from food. o metaballein = change mitochondria (my-toh-KON-dree-uh): the cellular organelles responsible for producing ATP aerobically; made of membranes (lipid and protein) with enzymes mounted on them. (The singular is mitochondrion.) o mitos = thread (referring to their slender shape) o chondros = cartilage (referring to their external appearance) oxaloacetate (OKS-ah-low-AS-eh-tate): a carbohydrate intermediate of the TCA cycle. © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-3 photosynthesis: the process by which green plants use the sun’s energy to make carbohydrates from carbon dioxide and water. o photo = light o synthesis = put together (making) pyruvate (PIE-roo-vate): a 3-carbon compound that plays a key role in energy metabolism. TCA cycle or tricarboxylic (try-car-box-ILL-ick) acid cycle: a series of metabolic reactions that break down molecules of acetyl CoA to carbon dioxide and hydrogen atoms; also called the citric acid cycle or the Krebs cycle after the biochemist who elucidated its reactions. o neo = new o genesis = making Alcohol Terms acetaldehyde (ass-et-AL-duh-hide): an intermediate in alcohol metabolism. alcohol: a class of organic compounds containing hydroxyl (OH) groups. o ol = alcohol alcohol abuse: a pattern of drinking that includes failure to fulfill work, school, or home responsibilities; drinking in situations that are physically dangerous (as in driving while intoxicated); recurring alcoholrelated legal problems (as in aggravated assault charges); or continued drinking despite ongoing social problems that are caused by or worsened by alcohol. alcohol dehydrogenase (dee-high-DROJ-eh-nayz): an enzyme active in the stomach and the liver that converts ethanol to acetaldehyde. alcoholism: a pattern of drinking that includes a strong craving for alcohol, a loss of control and an inability to stop drinking once begun, withdrawal symptoms (nausea, sweating, shakiness, and anxiety) after heavy drinking, and the need for increasing amounts of alcohol to feel “high.” antidiuretic hormone (ADH): a hormone produced by the pituitary gland in response to dehydration (or a high sodium concentration in the blood) that stimulates the kidneys to reabsorb more water and therefore to excrete less. In addition to its antidiuretic effect, ADH elevates blood pressure and so is also called vasopressin (VAS-oh-PRES-in). beer: an alcoholic beverage traditionally brewed by fermenting malted barley and adding hops for flavor. binge drinking: pattern of drinking that raises blood alcohol concentration to 0.08 percent or higher, usually corresponds to four or more drinks for women and five or more drinks for men on a single occasion, generally within a couple of hours. cirrhosis (seer-OH-sis): advanced liver disease in which liver cells turn orange, die, and harden, permanently losing their function; often associated with alcoholism. o cirrhos = an orange drink: a dose of any alcoholic beverage that delivers ½ ounce of pure ethanol: o 5 ounces of wine o 10 ounces of wine cooler o 12 ounces of beer o 1½ ounces of liquor (80 proof whiskey, scotch, rum, or vodka) drug: a substance that can modify one or more of the body’s functions. ethanol: a particular type of alcohol found in beer, wine, and liquor; also called ethyl alcohol (see Figure H7-1). Ethanol is the most widely used and abused—drug in our society. It is also the only legal, nonprescription drug that produces euphoria. excessive drinking: heavy drinking, binge drinking, or both. fatty liver: an early stage of liver deterioration seen in several diseases, including kwashiorkor and alcoholic liver disease. Fatty liver is characterized by an accumulation of fat in the liver cells. fibrosis (fye-BROH-sis): an intermediate stage of liver deterioration seen in several diseases, including viral hepatitis and alcoholic liver disease. In fibrosis, the liver cells lose their function and assume the characteristics of connective tissue cells (fibers). heavy drinking: consuming an average of more than one drink per day for women and more than two drinks per day for men. liquor or distilled spirits: an alcoholic beverage traditionally made by fermenting and distilling a carbohydrate source such as molasses, potatoes, rye, beets, barley, or corn. MEOS or microsomal (my-krow-SOmal) © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-4 ethanol-oxidizing system: a system of enzymes in the liver that oxidize not only alcohol but also several classes of drugs. moderation (alcohol): up to one drink per day for women with no more than three drinks on any single day and up to two drinks per day for men with no more than four drinks on any single day. narcotic (nar-KOT-ic): a drug that dulls the senses, induces sleep, and becomes addictive with prolonged use. proof: a way of stating the percentage of alcohol in distilled liquor. Liquor that is 100 proof is 50 percent alcohol; 90 proof is 45 percent, and so forth. Wernicke-Korsakoff (VER-neekey KORE-sah-kof) syndrome: a neurological disorder typically associated with chronic alcoholism and caused by a deficiency of the B vitamin thiamin; also called alcohol related dementia. wine: an alcoholic beverage traditionally made by fermenting a sugar source such as grape juice. Lecture Presentation Outline Key to instructor resource annotations (shown to the right of or below outline topics): Website = Available for download from book companion website: HN = student handout IM = Included in this instructor’s manual: CS = case study, WS = worksheet, CA = classroom activity Introductory/whole chapter resources: PL figure JPEGs; Test Bank; IM WS 7-5 I. Chemical Reactions in the Body – Explain the following: A. The Site of Metabolic Reactions—Cells – Metabolic reactions take place inside of cells (Figure 7-1) B. The Building Reactions—Anabolism (Figure 7-2) C. The Breakdown Reactions—Catabolism IM WS 7-1, 7-2 D. The Transfer of Energy in Reactions—ATP (Figure 7-3) 1. Adenosine triphosphate (ATP) (Figure 7-4) 2. Coupled reactions E. The Helpers in Metabolic Reactions—Enzymes and Coenzymes – Enzymes and coenzymes are helpers in reactions 1. Enzymes 2. Coenzymes 3. Cofactors II. Breaking Down Nutrients for Energy (Figure 7-5) IM CA 7-1, 7-2 A. Glucose IM WS 7-3 1. Glucose-to-Pyruvate – Glycolysis (Figure 7-6) 2. Pyruvate’s Options—Anaerobic or Aerobic a. Anaerobic – lactate b. Aerobic – acetyl CoA 3. Pyruvate-to-Lactate (Anaerobic) (Figure 7-7) a. Oxygen is not available or cells lack sufficient mitochondria b. Lactate c. Cori cycle 4. Pyruvate-to-Acetyl CoA (Aerobic) – Is irreversible (Figures 7-8, 7-9, and 7-10) B. Glycerol and Fatty Acids IM HN 7-1 1. Glycerol-to-Pyruvate – Conversion of glycerol to pyruvate 2. Fatty Acids-to-Acetyl CoA – Fatty acid oxidation 3. Fatty Acids Cannot Make Glucose – Fatty acids cannot be used to synthesize glucose (Figures 7-11 and 7-12) C. Amino Acids (Figure 7-13) 1. Amino Acid Deamination 2. Amino Acid Pathways © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-5 D. The Final Steps of Energy Metabolism 1. The TCA Cycle – The TCA cycle contains a 4-carbon compound called oxaloacetate that has a critical role (Figures 7-14 and 7-15) 2. The Electron Transport Chain (Figure 7-16) a. Consumes oxygen b. Produces carbon dioxide and water c. Produces energy as ATP 3. The kCalories-per-Gram Secret Revealed (Figures 7-17 and 7-18) a. Fat, with more C-H bonds than other nutrients, provides 9 kcal/gram b. Carbohydrate provides 4 kcal/gram c. Protein provides 4 kcal/gram III. Feasting and Fasting A. Feasting—Excess Energy 1. Excess Protein – Is converted to fat but this is inefficient and indirect 2. Excess Carbohydrate – Is converted to fat but this is inefficient and indirect. 3. Excess Fat – Is efficiently converted to fat B. The Transition from Feasting to Fasting – Draws on reserves (Figure 7-19) C. Fasting—Inadequate Energy 1. Adaptation: Making Glucose – Produced from some amino acids (from proteins) and glycerol (from triglycerides) 2. Adaptation: Creating an Alternate Fuel a. The shift to ketosis occurs when the brain becomes fueled by ketone bodies b. Ketones (Figure 7-20) c. Ketosis causes a suppression of the appetite d. Hormones slow the metabolism 3. Adaptation: Conserving Energy – Symptoms of starvation: a. Muscle wasting b. Decreased heart rate, respiratory rate, metabolic rate, and body temperature c. Impaired vision d. Organ failure e. Decreased immunity f. Depression, anxiety, and food-related dreams D. Low-Carbohydrate Diets 1. Result in changes in metabolism similar to what occurs during fasting 2. Ketones will be present in the urine when glycogen depletion has occurred 3. When a dieter returns to a well-balanced diet, the body will retain depleted nutrients IV. Highlight: Alcohol in the Body A. Alcohol in Beverages (Figure H7-1) 1. Beer, wine, and distilled liquor (hard liquor) 2. Alcohol behaves like a drug 3. Moderation of drinks (Figure H7-2 and H7-3) a. 5 ounces of wine b. 10 ounces of wine cooler c. 12 ounces of beer d. 1 ½ ounces distilled liquor (80 proof) B. Alcohol’s Influence 1. In the GI Tract a. Quickly absorbed b. Carbohydrates decrease the absorption of alcohol c. Alcohol dehydrogenase breaks down alcohol in the stomach d. Women absorb more alcohol then men 2. In the Liver (Figures H7-4 and H7-5) a.. Accumulation of fatty acids b. Alcohol dehydrogenase breaks down alcohol to acetaldehyde IM WS 7-4 © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-6 c. Alcohol abuse has damaging effects. d. Coenzyme NAD e Fatty liver f. Fibrosis g. Cirrhosis h. Microsomal ethanol-oxidizing system (MEOS) 3. In the Brain (Figure H7-6) – Alcohol acts as a narcotic, anesthetizes pain C. Alcohol’s Damage 1. Dehydration – Alcohol suppresses antidiuretic hormone (ADH), resulting in the loss of body water 2. Malnutrition Website HN 7-2 a. Heavy drinkers may have inadequate food intake. b. Impaired nutrient metabolism will result from chronic alcohol abuse. c. Vitamin B6, folate, thiamin deficiencies d. Wernicke-Korsakoff syndrome is seen in chronic alcoholism 3. Short-Term Effects a. Accidents, fatalities, and breaking the law b. Binge drinking or heavy drinking can result in death 4. Long-Term Effects a. Abuse during pregnancy b. Third leading cause of preventable death c. Health effects of heavy alcohol consumption 1. Arthritis 2. Cancer 3. Fetal alcohol syndrome 4. Heart disease 5. Hyperglycemia 6. Hypoglycemia 7. Infertility 8. Kidney disease 9. Liver disease 10. Malnutrition 11. Nervous disorders 12. Obesity 13. Psychological disturbances D. Personal Strategies 1. Serve and consume nonalcoholic beverages 2. Drink slowly and consume alcohol moderately 3. Do not drive Case Study 7: Excessive Alcohol Use Steve Q. is a 52-year-old Hispanic male with a family history of alcoholism. He is 6 feet 1 inch tall and weighs 238 pounds, with much of his excess weight around his middle. He considers himself a social drinker although he has had two arrests for driving under the influence of alcohol. Steve recently has been diagnosed with diabetes and takes an oral medication to control his blood glucose. He also has high cholesterol and has recently started on a lipidlowering medication. Recent tests have revealed Steve has fatty liver, which concerns him. He also reports having occasional low blood glucose (hypoglycemia) and feeling shaky and dizzy. 1. How much alcohol can the liver process per hour? a. ½ ounce b. 1 ounce c. 1 ½ ounces d. 2 ounces e. 2 ½ ounces © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-7 2. How many ounces of 80 proof liquor are in a single serving? a. ½ ounce b. 1 ounce c. 1 ½ ounces d. 2 ounces e. 2 ½ ounces 3. If Mr. Q. drinks a quart of beer, how many servings of alcohol is he consuming? a. about 1 serving b. just over 2 servings c. nearly 3 servings d. about 4 servings e. almost 6 servings 4. The maximum rate of alcohol breakdown is determined by the amount of a. acetaldehyde. b. acetaldehyde dehydrogenase. c. alcohol dehydrogenase. d. acetate. e. acetyl CoA. 5. Mr. Q. is concerned about his recent fatty liver diagnosis. Which of the following is true of fatty liver? a. It rarely progresses, even if drinking continues. b. It is characterized by the formation of scar tissue. c. It is generally “silent” and rarely has effects on the liver or on health in general. d. In the early stages, it is reversible with abstinence from alcohol. e. Even with abstinence, it is likely to progress to cirrhosis. 6. Mr. Q. had blood alcohol concentrations well above the legal limit when he was arrested for his DUIs. At what blood alcohol concentration do unconsciousness, coma, and death become likely outcomes? a. 0.05 b. 0.10 c. 0.15 d. 0.20 e. 0.40 7. If Mr. Q continues drinking, how might alcohol affect his health? a. increased risk of colon cancer b. increased testosterone levels c. shrinking of kidneys d. decreased joint inflammation e. increased bone mass Answer Key 1. a 2. c 3. c 4. c 5. d 6. d 7. a © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-8 Classroom Activity 7-1: Enhancing Understanding of Metabolism4 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 miles per gallon) 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 proportions of fat and glucose burned during the activity. Car Human beings Car Human beings 4 Energy Obtained First gear Measure of Energy Miles/gallon Advantage Disadvantage Quick acceleration Glycolysis (anaerobic) High gear ATP TCA cycle (aerobic) ATP Quick, intense muscle activity Used to sustain desired velocity over maximum amount of time Used to sustain desired amount of muscle activity over maximum amount of time Can only be used for a few seconds of acceleration Can only be used for a few seconds as lactic acid is produced Depends on rate of oxygen delivery to fuel source; better tuned engines achieve maximum miles/gallon Depends on rate of oxygen delivery to fuel source; better conditioning improves rate of oxygen delivery Miles/gallon Activity provided by: Samantha Logan, DrPH, University of Massachusetts, Amherst © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-9 Worksheet 7-5: Chapter 7 Crossword Puzzle 1 2 3 4 5 6 7 8 9 10 11 Across: Adenosine triphosphate (ATP) molecules are used to capture and store _____ during metabolism. 3. The number of _____ molecules relates to the amount of energy a nutrient can provide. 6. Making of glucose from non-carbohydrate substances 8. Referred to as the sum of all chemical reactions in living cells 9. Body organ that contains the most metabolically active cells 11. Fatty acids cannot be converted to _____ so they cannot generate glucose. 2. Down: Splitting a glucose molecule, or _____, is the first step in energy metabolism. 2. Carbohydrates, fat, and protein are referred to as _____ nutrients. 4. An alternative energy source designed to prolong life during starvation 5. Processes that occur without oxygen 7. Harmful effect of excessive alcohol intake that can be reversible 10. Energy-yielding nutrient that provides the most kcalories per gram 1. © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. Chapter 7-10 Handout 7-1: The Carbons of a Typical Triglyceride A typical triglyceride contains only one small molecule of glycerol (3 C) but has three fatty acids (each commonly 16 C or 18 C, or about 48 C to 54 C in total). Only the glycerol portion of a triglyceride can yield glucose. © 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use.