Nutrition & Metabolism Chapter 19 PDF

Nutrition & Metabolism Chapter 19  Learning Objectives Lesson 19.1: Nutrition and Metabolism 1. Describe the role of the liver in metabolism. 2. Describe the metabolic roles of carbohydrates, fats, proteins, vitamins, and minerals. 3. Describe me...

Nutrition & Metabolism Chapter 19  Learning Objectives Lesson 19.1: Nutrition and Metabolism 1. Describe the role of the liver in metabolism. 2. Describe the metabolic roles of carbohydrates, fats, proteins, vitamins, and minerals. 3. Describe mechanisms that regulate food intake, and define basal metabolic rate, as well as list some factors that affect basal metabolic rate. 4. List and describe three conditions associated with eating or metabolism. 5. Discuss the physiological mechanisms that regulate body temperature.  Definitions (1 of 2)  Nutrition: Food, vitamins, and minerals that are ingested and assimilated into the body  Metabolism: Process of using nutrient molecules as energy sources and as building blocks for our own molecules  Definitions (2 of 2)  Catabolism: Process that breaks food molecules down, releasing their stored energy; oxygen used in catabolism  Anabolism: Process that builds nutrient molecules into complex chemical compounds  Food Guide From the U.S. Department of Agriculture, Center for Nutrition Policy and Promotion. USDA’s MyPlate home page (website): www.choosemyplate.gov. Accessed August 29, 2016. Metabolic Function of the Liver  Secretes bile to help mechanically digest lipids  Processes blood immediately after it leaves the gastrointestinal tract  Helps maintain normal blood glucose concentration  Site of protein, carbohydrate, and fat metabolism  Removes toxins from the blood  Synthesizes several kinds of protein compounds, such as albumins, fibrinogen, clotting factors  Stores some vitamins  Macronutrients  “Big three” nutrients in our diets are carbohydrates, lipids, and proteins  Vitamins and minerals are called micronutrients  Carbohydrate Metabolism (1 of 2)  Carbohydrates are the preferred energy nutrient of the body  Three series of chemical reactions that occur in a precise sequence make up the process of glucose metabolism  Glycolysis: Occurs in cytoplasm of the cell Anaerobic process (uses no oxygen) Changes glucose to pyruvic acid, which is then converted into acetyl CoA Yields small amount of energy (transferred to ATP)  Carbohydrate Metabolism (2 of 2)  Energy transferred to ATP differs from energy in nutrient molecules  Not stored; released almost instantly  Can be used directly to do cellular work  Carbohydrates primarily catabolized for energy, but small amounts anabolized by glycogenesis (series of chemical reactions that changes glucose to glycogen: Occurs mainly in liver cells where glycogen is stored) Metabolism of Glucose  Citric Acid (Krebs) Cycle  Occurs in the mitochondria  Aerobic process (requires oxygen)  Changes acetyl CoA to carbon dioxide  Yields small amount of energy  Most energy leaving the citric acid cycle is in the form of high-energy electrons Adenosine Triphosphate (ATP)  Blood Glucose  Blood glucose (imprecisely, blood sugar): Amount of glucose in blood  Normally stays at about 80 to 110 mg per 100 mL of blood during fasting  Insulin accelerates the movement of glucose out of the blood into cells; therefore, decreases blood glucose and increases glucose catabolism  Fat and Protein Metabolism  Fat metabolism  Fats are primarily an energy nutrient  Converted to glucose by catabolism  Excess fat is anabolized to form adipose tissue  Protein metabolism  Proteins are catabolized for energy only after carbohydrate and fat stores have been depleted  Gluconeogenesis breaks apart amino acids to convert them to glucose Catabolism of Nutrients  Vitamins  Organic molecules that are needed in small amounts for normal metabolism (Table 19-3)  Avitaminosis: Deficiency of a vitamin Can lead to severe metabolic problems Avitaminosis C can lead to scurvy  Hypervitaminosis: Excess of a vitamin Can be just as serious as avitaminosis May be chronic or acute  Functions of Vitamins  Most vitamins attach to enzymes or coenzymes to help them work properly  Many enzymes are totally useless without the appropriate vitamins to activate them  Vitamin A plays an important role in detecting light in the sensory cells of the retina  Vitamin D can be converted to a hormone that helps regulate calcium homeostasis in the body  Vitamin E acts as an antioxidant that prevents highly reactive molecules called  Minerals  Inorganic molecules found naturally in the earth  Required by the body for normal function, including nerve conduction  Can attach to enzymes to facilitate their work  Regulating Food Intake  Appetite center promotes feeling of hunger  Satiety center that promotes the feeling of being “full” or “satisfied”  Metabolic Rates  Basal metabolic rate (BMR): Rate of metabolism when a person is lying down but awake and not digesting food and when the environment is comfortably warm  Total metabolic rate (TMR): The total amounts of energy, expressed in calories, used by the body per day Basal and Total Metabolic Rates  Metabolic Conditions  Disruption or imbalance of normal metabolism can be caused by several different factors  Inborn errors of metabolism: Genetic conditions involving deficient or abnormal metabolic enzymes  Some metabolic conditions are complications of other conditions Hormonal imbalances  Eating Conditions  Anorexia nervosa: Characterized by chronic refusal to eat  Bulimia: An alternating pattern of craving of food followed by a period of self-denial; in bulimarexia, the self- denial triggers self-induced vomiting  Obesity: Abnormally high proportion of fat in the body; may be a symptom of an eating disorder  Protein-Calorie Malnutrition (PCM) (1 of 2)  Results from a deficiency of calories in general and proteins in particular  May be a complication of a preexisting condition  Marasmus: Type of advanced PCM caused by an overall lack of calories and protein, characterized by tissue wasting and fluid and electrolyte imbalances  Kwashiorkor: Type of advanced PCM caused by a lack of protein in the presence of sufficient calories; similar to marasmus but distinguished by ascites and flaking dermatitis Protein-Calorie Malnutrition (PCM) (2 of 2)  Body Temperature (1 of 2)  Hypothalamus: Regulates the homeostasis of body temperature (thermoregulation) through a variety of processes  Blood flow to the skin increases when body is overheated  Heat is lost through the skin by radiation, conduction, convection, evaporation Body Temperature (2 of 2)  Abnormal Body Temperature  Abnormal body temperature can have serious physiological consequences  Fever (febrile state): Unusually high body temperature associated with systemic inflammation response  Malignant hyperthermia (MH): Inherited condition that causes increased body temperature (hyperthermia) and muscle rigidity when exposed to certain anesthetics Heat Exhaustion and Heatstroke  Heat exhaustion: Results from loss of fluid as the body tries to cool itself; may be accompanied by heat cramps  Heatstroke (sunstroke): Overheating of body resulting from failure of thermoregulatory mechanisms in a warm environment  Hypothermia and Frostbite  Hypothermia: Reduced body temperature resulting from failure of thermoregulatory mechanisms in a cold environment  Frostbite: Local tissue damage caused by extreme cold; may result in necrosis or gangrene Questions?