Chapter 27 Lecture Outline PDF

1 Chapter 27 Lecture Outline © 2019 McGraw-Hill Education 27.1 Introduction to Nutrition Learning Objectives: 1. Define both nutrition and nutrients. 2. Distinguish macronutrients from micronutrients and essential from nonessential nutrients. 3. Explain the meaning of recommended daily allowanc...

1 Chapter 27 Lecture Outline © 2019 McGraw-Hill Education 27.1 Introduction to Nutrition Learning Objectives: 1. Define both nutrition and nutrients. 2. Distinguish macronutrients from micronutrients and essential from nonessential nutrients. 3. Explain the meaning of recommended daily allowance (RDA). © 2019 McGraw-Hill Education 2 3 27.1 Introduction to Nutrition 1 Nutrition—study of how living organisms obtain and utilize nutrients needed to grow and sustain life Nutrients • Include most biomolecules, vitamins, and minerals • Required for synthesis of new molecules • Required for energy for maintenance, growth, and repair • Obtained through food • Water is considered a nutrient • Levels regulated during and following meals © 2019 McGraw-Hill Education 4 27.1 Introduction to Nutrition Categories of nutrients • Macronutrients • Must be consumed in relatively large quantities • Needed in daily amounts • Carbohydrates, lipids, proteins • Micronutrients • Must be consumed in relatively small quantities • Vitamins and minerals • Essential • Must be obtain and absorbed via digestive system from diet • Nonessential • Provided by biochemical processes of body • Not required in diet © 2019 McGraw-Hill Education 2 5 27.1 Introduction to Nutrition 3 Recommended daily allowance (RDA) • Amount of each nutrient that must be obtained each day • Established values for nutrients set by federal agencies • Originally established by Food and Nutrition Board • Reviewed and updated periodically • Used for food planning, food labeling, education, etc. • In the future your RDA could be based on your genetic makeup © 2019 McGraw-Hill Education 6 Section 27.1 What did you learn? 1. List the six nutrients required by the body. 2. Distinguish between macronutrients and micronutrients. 3. What is meant by the RDA of nutrients? © 2019 McGraw-Hill Education 27.2 Macronutrients Learning Objectives: 4. Identify the categories that are dietary sources of carbohydrates, and give examples of each category. 5. Identify the types and dietary sources of triglycerides, and describe their function. 6. Describe the sources and functions of cholesterol. 7. Describe why protein is required in our diet and the general amount that is needed. 8. Explain the difference between a complete protein and an incomplete protein. 9. Discuss nitrogen balance, and include the difference between a positive and negative nitrogen balance. © 2019 McGraw-Hill Education 7 8 27.2 Macronutrients All macronutrients provide fuel for cellular respiration to form ATP (i.e., they provide energy) This energy is measure in calories • A calorie the amount of heat required to raise the temperature of 1 g of water by 1C • Kilocalorie 1000 calories, 1 Calorie Body weight is maintained when calories consumed and calories expended are in balance © 2019 McGraw-Hill Education 9 27.2a Carbohydrates 1 Carbohydrates • Structurally classified as • Monosaccharides, Disaccharides, Polysaccharides • When describing dietary sources, classified as • Sugars – glucose, lactose, etc. • Starch – polysaccharide in potatoes and grains • Fiber – not easily digested – whole grain, nuts, beans © 2019 McGraw-Hill Education 10 27.2a Carbohydrates 4 Sugars and starch usually converted to glucose • Primary energy-supplying nutrient • Glucose not considered essential • Can be synthesized from other monosaccharides by gluconeogenesis Fiber serves different purpose • Adds bulk • Stimulates peristalsis • “Keeps you regular” • Lowers cholesterol © 2019 McGraw-Hill Education 11 27.2b Lipids 1 Lipids include • Triglycerides • Phospholipids • Steroids Triglycerides—composed of glycerol and fatty acids Fatty acids organized into 3 categories—saturated, unsaturated, polyunsaturated © 2019 McGraw-Hill Education Saturated fatty acids 27.2b Lipids 12 2 • No double bond -solid at room temperature • Dietary sources -Fat in meat, milk, cheese, coconut oil Unsaturated fatty acids • One double bond -liquid at room temperature • Dietary sources- nuts, certain oils—canola oil, olive oil Polyunsaturated fatty acids • Two or more double bonds liquid at room temperature • Dietary sources —soybean oil, corn oil, safflower oil Cholesterol • Component of plasma membrane and precursor for steroid hormones, bile salts, vitamin D • Comes from diet or metabolic pathway in liver © 2019 McGraw-Hill Education 13 27.2c Proteins 1 Proteins most structurally and functionally diverse molecules Needed in adequate quantities to replace worn out protein structures • Amount needed depends on age and sex • More needed to fight an infection, following an injury, stressful conditions, pregnancy • Infants and children also need more for growth 8 amino acids are essential, other 12 can be synthesized in the body © 2019 McGraw-Hill Education 14 27.2c Proteins 2 Complete proteins • Contain all essential amino acids • Generally animal proteins Incomplete proteins • Do not contain all essential amino acids • Generally plant proteins • Combinations of dishes containing plant proteins can provide all essential amino acids • No storage of excess, so must be supplied regularly © 2019 McGraw-Hill Education Amino Acids 10 amino acids we produce alanine Essential amino acids required in diet asparagine arginine aspartic acid histidine cysteine isoleucine glutamic acid leucine glutamine lysine glycine methionine proline phenylalanine serine threonine Tyrosine -produced from phenylalanine tryptophan © 2019 McGraw-Hill Education valine 15 16 27.2c Proteins 3 Vegetarian—Does not eat meat, poultry, fish • Lacto-ovo vegetarians • Do not eat animal flesh, but eat milk, eggs, and cheese • Vegans • Do not eat any animal products • Plant-based protein sources often individually incomplete • Must obtain essential amino acids through complementary protein sources • Not necessarily eaten at the same meal, but regularly © 2019 McGraw-Hill Education 17 27.2c Proteins 4 Nitrogen balance • Proteins are a source of nitrogen • Needed for synthesizing nitrogen-containing molecules • E.g., DNA, RNA • When equilibrium exists between dietary intake and loss • Positive nitrogen balance, absorbing more nitrogen than excreted • E.g., during growth, pregnancy, recovering from injury • Negative nitrogen balance, more nitrogen excreted than absorbed • E.g., during blood loss, malnutrition • Can be fatal © 2019 McGraw-Hill Education 18 Section 27.2 What did you learn? 4. What is the general function of both sugars and starch in our diet? 5. How does dietary fiber differ from other dietary carbohydrates? 6. What are two primary functions of fats? 7. Explain the general difference in animal proteins and plant proteins in terms of obtaining essential amino acids. 8. How may a vegetarian obtain all of the essential amino acids? © 2019 McGraw-Hill Education 27.3 Micronutrients Learning Objectives: 10. Distinguish between water-soluble and fat-soluble vitamins. 11. List examples of how both water-soluble and fat-soluble vitamins function in the body. 12. Describe the difference between essential and nonessential vitamins 13. Define minerals, and list examples of how minerals absorbed in the small intestine function in the body. 14. Distinguish between major minerals and trace minerals. © 2019 McGraw-Hill Education 19 20 27.3a Vitamins 1 Vitamins • Organic molecules required for normal metabolism • Present in only small amounts in food • Water-soluble or fat-soluble • Essential or nonessential Water-soluble vitamins • Dissolve in water • B vitamins serve as coenzymes • Vitamin C required for collagen synthesis; antioxidant • Easily absorbed into blood from digestive tract • Excess excreted in urine © 2019 McGraw-Hill Education 21 27.3a Vitamins 2 Fat-soluble vitamins • Dissolve in fat • Vitamins A, D, E, and K • Absorbed from GI tract within micelles • Excess stored in fat • May become toxic if taken in excess • Functions • Vitamin A, precursor of visual pigment retinal • Vitamin D, forms calcitriol, increases calcium absorption from GI tract • Vitamin E, stabilizes and prevents damage to cell membranes • Vitamin K, required for synthesis of blood clotting proteins © 2019 McGraw-Hill Education 22 27.3a Vitamins 3 Essential and nonessential vitamins • Essential vitamins • Necessary from diet • Deficiency if intake or absorption is impaired • E.g., vitamin C, Vitamin A • Nonessential vitamins • Cofactors body produces and recycles as needed • E.g., NADH, FADH2 © 2019 McGraw-Hill Education 23 27.3b Minerals 1 Minerals • Inorganic ions obtained from diet • Required in daily amounts • Iron • In hemoglobin, binds oxygen • In mitochondria, in electron transport system binds electrons • Calcium • Required for formation and maintenance of skeleton and muscle contraction, blood clotting, and exocytosis of neurotransmitters © 2019 McGraw-Hill Education 24 27.3b Minerals 2 Minerals (continued) • Sodium and potassium • Maintain resting membrane potential in excitable cells • Required to generate action potential • Iodine • Needed to produce thyroid hormone • Zinc • Roles in protein synthesis and wound healing All minerals are essential and must be obtained from the diet © 2019 McGraw-Hill Education 25 27.3b Minerals 3 Minerals (continued) • Major minerals • >100 mg/day required • E.g., calcium, chloride, potassium, phosphorus, magnesium, etc. • Trace minerals • <100 mg/day required • E.g., chromium, copper, iodine, iron, zinc, etc. • Stored to varying degrees within body © 2019 McGraw-Hill Education 26 Clinical View: Iron Deficiency Iron required in hemoglobin and myoglobin Component of electron transport proteins Needed to synthesize • Certain hormones, neurotransmitters, and amino acids Obtained from: • Meat, poultry, fish, dark leafy vegetables, nuts, and whole grains Most common nutritional deficiency Fatigue, weakness, pale skin, and sensitivity to cold Insufficient intake or iron loss • E.g., excessive loss from bleeding © 2019 McGraw-Hill Education 27 Section 27.3 What did you learn? 9. Which vitamins are water-soluble? Which are fat-soluble? Which of these groups may be dangerous in excess? 10. What are the major minerals? The trace minerals? How are these two groups distinguished? © 2019 McGraw-Hill Education 27.4 Guidelines for Adequate Nutrition Learning Objectives: 15. Describe MyPlate, which was developed by the USDA to help people eat healthy. 16. Identify the items that are included on a food label. © 2019 McGraw-Hill Education 28 29 27.4 Guidelines for Adequate Nutrition MyPlate • United States Department of Agriculture (USDA) recommendation • Visual representation of desired proportions of food Figure 27.1 © 2019 McGraw-Hill Education 1 30 27.4 Guidelines for Adequate Nutrition Nutritional food labels • Provide details on composition of prepackaged items • Serving size, calories, total fat, cholesterol, sodium, etc. • Helpful for meal planning • To promote health in well individuals • For those with special dietary needs Figure 27.2 © 2019 McGraw-Hill Education 2 31 Section 27.4 What did you learn? 11. What categories of food are shown on the USDA MyPlate? Which food category takes up the largest portion of the plate? 12. What is the purpose of the requirement for nutritional labeling on packaged foods? © 2019 McGraw-Hill Education 27.5 Regulating Blood Levels of Nutrients 32 Learning Objectives: 17. Explain when the absorptive state occurs and how nutrient levels are regulated during this time. 18. Explain when the postabsorptive state occurs and how nutrient levels are regulated during this time. © 2019 McGraw-Hill Education 33 27.5a Absorptive State 1 Absorptive state • Time eating, digesting, and absorbing nutrients • Lasts 4 hrs after a meal • Concentrations of glucose, triglycerides, and amino acids increased as absorbed from GI tract • Blood glucose levels maintained within 70 to 110 mg/dL © 2019 McGraw-Hill Education 34 27.5a Absorptive State 2 Insulin • Major regulatory hormone released during absorptive state • Released from pancreas in response to increased blood glucose levels • Stimulates liver and muscle cells • Form glycogen from glucose • Affects adipose tissue • Increases uptake of triglycerides from blood • Stimulates lipogenesis and inhibits lipolysis • Stimulates most cells to increase amino acid uptake • Causes accelerated protein synthesis © 2019 McGraw-Hill Education 35 27.5b Postabsorptive State Postabsorptive state • Time between meals • Body relying on stores of nutrients • Body working to maintain homeostatic levels of nutrients Glucagon • Major regulatory hormone during postabsorptive state • Released in response to decreasing blood glucose levels • Stimulates: • Liver to increase breakdown of glycogen to glucose • Gluconeogenesis from noncarbohydrate sources • Adipose tissue to break down triglycerides • No effect on amino acids or proteins in cells © 2019 McGraw-Hill Education 36 Section 27.5 What did you learn? 13. How does the storage of nutrient molecules change during the absorptive state? 14. What is the major regulatory hormone in the postabsorptive state, and what are its functions? © 2019 McGraw-Hill Education 27.6 Functions of the Liver Learning Objectives: 19. Explain the relationship of dietary intake of cholesterol and level of cholesterol synthesis in the liver. 20. Define a lipoprotein, and provide a general overview of their function in the body. 21. Describe the transport of lipids within the blood. 22. Identify and briefly describe the numerous roles of the liver in metabolism. (see Ch26) © 2019 McGraw-Hill Education 37 38 27.6a Cholesterol Synthesis Cholesterol synthesis • Synthesized by hepatocytes • Fatty acids transported in blood to enter hepatocytes • Cholesterol produced at basal level, varies among individuals • Synthesis decreased with higher cholesterol intake and vice versa • Following its formation • Released into blood in very-low-density lipoproteins, or • Synthesized into bile salts as part of bile • 90% of these reabsorbed while moving through ileum • 10% lost in feces © 2019 McGraw-Hill Education 39 27.6b Transport of Lipids 1 Lipoproteins • Lipids with protein “wrap” to facilitate transport • E.g., chylomicrons • Lipoproteins form in liver • Very-low-density lipoproteins (VLDL), contain the most lipid • Low-density lipoproteins (LDL) with less lipid • High-density lipoproteins (HDL) with least amount of lipid © 2019 McGraw-Hill Education 40 Clinical View: Blood Cholesterol Levels LDL and HDL levels: • Risk factors for cardiovascular disease • Above 200 mg/dL total cholesterol considered “high” LDLs considered “bad cholesterol” • Excess cholesterol deposited on inner arterial walls HDLs considered “good cholesterol” • Transport lipid from arterial wall to liver © 2019 McGraw-Hill Education 1 41 Clinical View: Blood Cholesterol Levels Risk factors correlated with high cholesterol • High saturated fat intake, cigarette smoking, caffeine intake, and stress Statin drugs • Developed to lower blood cholesterol • Inhibitor for HMG-CoA, enzyme needed for cholesterol synthesis © 2019 McGraw-Hill Education 2 42 Section 27.6 What did you learn? 15. Is cholesterol synthesis increased or decreased in response to high dietary intake of cholesterol? 16. What are the two fates of cholesterol following its synthesis? © 2019 McGraw-Hill Education 27.7 Central Role of Cellular Respiration Learning Objectives: 23. Describe where the following nutrient molecules enter the metabolic pathway of cellular respiration: glucose, the breakdown products of triglycerides, and amino acids. 24. Explain deamination of proteins. 25. Describe the physiologic advantages of the ability to interconvert nutrient biomolecules. © 2019 McGraw-Hill Education 43 44 27.7a ATP Generation 1 Four stages of cellular respiration 1. Glycolysis • Anaerobic metabolic pathway in cytoplasm • Glucose oxidized to 2 pyruvate molecules • 2 ATP formed, 2 NADH formed from NAD+ • Pyruvate converted to lactate if insufficient O2 available 2. Intermediate stage • This and following steps, aerobic and within the mitochondria • Pyruvate converted to acetyl CoA • CO2 formed and NADH produced © 2019 McGraw-Hill Education 45 27.7a ATP Generation 2 Four stages of cellular respiration (continued) 3. Citric acid cycle • Acetyl CoA forms citric acid • CO2, ATP, FADH2, and NADH produced in cycle “turn” 4. Electron transport system • Transfer of hydrogen and electron from NADH and FADH2 • ATP formed through oxidative phosphorylation © 2019 McGraw-Hill Education 46 27.7a ATP Generation 3 Glycerol and fatty acids • Building blocks of triglycerides • Glycerol enters pathway of glycolysis • Converted to glucose within the liver • Carbons of fatty acids removed to form acetyl CoA • Beta oxidation • Molecules enter citric acid cycle © 2019 McGraw-Hill Education 47 27.7a ATP Generation 4 Amino acids • May be used to generate ATP • Amine group of amino acids removed by deamination • Occurs within liver hepatocytes • Amine group converted to urea • Eliminated through kidney in urine • Remainder enters metabolic pathway at different steps • Depends on specific amino acid • May enter glycolysis, intermediate stage, or citric acid cycle © 2019 McGraw-Hill Education 27.7b Interconversion of Nutrient Biomolecules and Their Building Blocks Nutrient interconversion • Changing of one nutrient biomolecule into another • Due to biochemical pathways associated with cellular respiration • E.g., glucose broken down to acetyl CoA • Then synthesized into triglycerides and stored • Instead of entering citric acid cycle • E.g., protein and fat consumed in low-carbohydrate diet • Reversal of biochemical pathways of cellular respiration • Converted to glucose © 2019 McGraw-Hill Education 48 Cellular Respiration: Generation of ATP Molecules and Interconversion of Nutrient Molecules Figure 27.6 © 2019 McGraw-Hill Education 49 50 Section 27.7 What did you learn? 19. Where in the biochemical pathway of cellular respiration (glycolysis, intermediate stage, or citric acid cycle) does each of the following enter: (a) glycerol, (b) fatty acids, and (c) deaminated amino acids? 20. How is excess sugar (glucose) converted to fat (triglycerides)? © 2019 McGraw-Hill Education 27.8 Energy and Heat Learning Objectives: 26. Define metabolic rate. 27. Explain how both basal metabolic rate and total metabolic rate are measured and the variables that influence each. 28. Define core body temperature, and explain why it must be maintained. 29. Explain the neural and hormonal controls of temperature regulation. © 2019 McGraw-Hill Education 51 52 27.8a Metabolic Rate 1 Metabolic rate • Measure of energy used in a given period of time • Basal metabolic rate and total metabolic rate Basal metabolic rate (BMR) • Amount of energy used at rest • Resting conditions: individual has not eaten for 12 hours, is relaxed, temperature about 20°C • Measured by calorimeter or respirometer © 2019 McGraw-Hill Education 53 27.8a Metabolic Rate 3 Basal metabolic rate (BMR) (continued) • Varies due to age, lean body mass, sex, and levels of hormones in the blood • Decreases with age—3% each decade beginning ~30 • Greater lean body mass = higher BMR • Thyroid hormone increases BMR • Hypothyroidism = lower than normal BMR • Hyperthyroidism = higher than normal BMR © 2019 McGraw-Hill Education 54 27.8a Metabolic Rate 4 Total metabolic rate (TMR) • BMR + metabolism associated with physical activity • Depends on several factors • Amount of skeletal muscle and its activity • E.g., rapid increase during vigorous exercise • Food intake • E.g., increases following ingestion of a meal, but decreases after absorption • Changing environmental conditions • Increases if exposed to cold temperature © 2019 McGraw-Hill Education 55 27.8b Temperature Regulation 1 Temperature homeostasis • Variable heat produced due to variable metabolic rate • Body temperatures maintained within certain physiological limits • Near normal value of 98.6°F (37°C) • Neural and hormonal controls • Core body temperature • Temperature of vital portions of body—head and torso • Temperature kept relatively constant • Maintained by allowing fluctuations in peripheral regions © 2019 McGraw-Hill Education 56 27.8b Temperature Regulation 2 Nervous system control • Mediated through hypothalamus • Motor pathways to sweat glands, skeletal muscles, and peripheral blood vessels • Monitors temperature of blood • With increase in body temperature • Hypothalamus stimulates sweat glands • Vasodilates peripheral vessels © 2019 McGraw-Hill Education 57 27.8b Temperature Regulation 3 Nervous system control (continued) • With decrease in body temperature • Hypothalamus inhibits sweat glands • Vasoconstricts peripheral vessels • Induces skeletal muscles contraction to generate heat (shivering) • Behavior changes initiated in cortex in response to temperature • E.g., putting on a coat if cold • E.g., jumping into a pool when hot © 2019 McGraw-Hill Education 58 27.8b Temperature Regulation 4 Hormonal control • Mediated by multiple hormones • Thyroid, epinephrine, norepinephrine, growth hormone, and testosterone • Thyroid hormone, most significant • Establishes metabolic rate • Raises body temperature by increasing rate of all cells • If temperature drops, hypothalamus releases thyrotropinreleasing hormone • Stimulates thyroid-stimulating hormone from anterior pituitary • Stimulates thyroid gland to release thyroid hormones © 2019 McGraw-Hill Education 59 Clinical View: Heat-Related Illnesses Heat cramps • Involuntary muscle spasms from excessive loss of fluid • Intense physical activity in hot, humid weather Heat exhaustion • Core body temp up to 104°F • Headache, weakness, rapid HR, nausea, vomiting Heatstroke • Severe; may result from untreated heat exhaustion • Body temp 104°F or higher; unable to control it • Fever, lack of sweating, confusion, rapid breathing • Can be fatal © 2019 McGraw-Hill Education Clinical View: Hypothermia, Frostbite, and Dry Gangrene 60 Hypothermia Core body temperature below 95°F Decreased HR, slow breathing, confusion, drowsiness, fatigue Frostbite Damage to superficial cells due to extreme cold Skin white with possible loss of sensation Dry gangrene May be caused by severe frostbite Body part dry, distinct in color, shriveled Due to extensive vasoconstriction of blood vessels Oxygen deprivation and tissue death © 2019 McGraw-Hill Education 61 Section 27.8 What did you learn? 21. Would your total metabolic rate increase when you exited your home on a cold winter day? Explain. 22. What is the core body temperature, and why must it be maintained? 23. Explain the role of the hypothalamus in regulating the response to an increase in body temperature. © 2019 McGraw-Hill Education