Nutrition and Metabolism Chapter 17 Copyright © 2016 by Elsevier Inc. All rights reserved.

Learning Objectives Lesson 17.1: Nutrition and Metabolism Explain metabolism, and define and contrast catabolism and anabolism. Describe the metabolic roles of carbohydrates, fats, proteins, vitamins, and minerals. Define basal metabolic rate and list some factors that affect it. Discuss the physiological mechanisms that regulate body temperature. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Definitions Nutrition Food, vitamins, and minerals that are ingested and assimilated into the body (Figure 17-1) Metabolism Process of using food molecules as energy sources and as building blocks for our own molecules Catabolism Breaks food molecules down, releasing their stored energy; oxygen used in catabolism Anabolism Builds food molecules into complex substances Proper nutrition requires a balance of three basic food types: carbohydrates, fats, and proteins, plus essential vitamins and minerals. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Food Guide Figure 17-1: Canada, the United States, and many other countries provide online, individualized food guides that help people determine proper amounts and a healthy balance of nutrients. www.ChooseMyPlate.gov is hosted by the United States Department of Agriculture (USDA). Copyright © 2016 by Elsevier Inc. All rights reserved.

Metabolic Function of the Liver Secretes bile, which breaks down large fat globules Helps maintain normal blood glucose level Helps metabolize carbohydrates, fats, and proteins Synthesizes several kinds of protein compounds Removes toxins from the blood Hepatic portal vein delivers blood directly from the gastrointestinal tract to the liver. Liver cells carry on the first steps of protein and fat metabolism. These proteins, when released into blood, are called plasma proteins. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Macronutrients Dietary sources of nutrients Macronutrients: Carbohydrates, fats, and proteins Micronutrients: Vitamins and minerals Carbohydrate metabolism Carbohydrates are preferred energy food of the body Three series of chemical reactions in glucose metabolism (Figure 17-2) Glycolysis Changes glucose to pyruvic acid Anaerobic (uses no oxygen) Occurs in cytoplasm Glycolysis occurs in cytoplasm and yields small amount of energy, generating two adenosine triphosphate (ATP) molecules. Copyright © 2016 by Elsevier Inc. All rights reserved.

Macronutrients (Cont.) Carbohydrate metabolism Three series of chemical reactions in glucose metabolism Citric acid (Krebs) cycle Changes pyruvic acid to carbon dioxide Aerobic (requires oxygen) Occurs in mitochondria Electron transfer system (ETS) Transfers energy from high-energy electrons (from citric acid cycle) to ATP molecules Located in mitochondria Citric acid occurs in mitochondria and yields large amount of energy (mostly as high energy electrons). Electron transfer system is located in mitochondria and transfers energy. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Metabolism of Glucose Figure 17-2 shows the metabolism of glucose. Copyright © 2016 by Elsevier Inc. All rights reserved.

Macronutrients (Cont.) Carbohydrate metabolism The mitochondrial part of the pathway (citric acid cycle and electron transport system) is aerobic (requires oxygen) and generates up to 36 ATP molecules per original glucose molecule Carbohydrates are primarily catabolized for energy Adenosine triphosphate (ATP) Molecule in which energy obtained from breakdown of foods is stored Serves as a direct source of energy for cellular work (Figure 17-3) ATP is made up of an adenosine group and three phosphate groups. Copyright © 2016 by Elsevier Inc. All rights reserved.

Macronutrients (Cont.) Carbohydrate metabolism Storage of glucose Glucose that is not needed immediately for making ATP is stored as glycogen (a long chain of glucose subunits) in the liver and muscle cells Glycogenesis Anabolic process of joining glucose molecules together in a chain to form glycogen (to store glucose for later use) Glycogenolysis Catabolic process of breaking apart glycogen chains, releasing individual glucose molecules for use in making ATP Glycogenesis is carried on chiefly by liver and muscle cells. Copyright © 2016 by Elsevier Inc. All rights reserved.

Adenosine Triphosphate (ATP) Figure 17-3, A, shows the structure of ATP. B shows the ATP energy cycle. Copyright © 2016 by Elsevier Inc. All rights reserved.

Macronutrients (Cont.) Carbohydrate metabolism Blood glucose (imprecisely, blood sugar) Normally stays between about 80 and 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 metabolism Catabolized to yield energy and anabolized to form adipose tissue (Figure 17-4) Protein metabolism Primarily anabolized and secondarily catabolized Fats not needed for catabolism are anabolized to form triglycerides and stored in adipose tissue. Only about half of the required 20 types of amino acids can be made by the body; the remaining must be supplied in diet. Copyright © 2016 by Elsevier Inc. All rights reserved.

Catabolism of Nutrients Figure 17-4: Fats, carbohydrates, and proteins can be converted to products that enter the citric acid cycle to yield energy. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Micronutrients Vitamins Organic molecules that are needed in small amounts for normal metabolism (Table 17-3) Minerals Inorganic molecules found naturally in the earth, required by the body for normal function (Table 17-4) Most vitamins cannot be made in the body, so we must eat them in our food. Without essential minerals, the brain, heart, and respiratory tract would cease to function. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Major Vitamins Table 17-3 shows the major vitamins, their dietary sources, their functions, and the consequences of deficiency. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Major Minerals Table 17-4 shows major minerals, their dietary sources, their functions, and symptoms of deficiency. Copyright © 2016 by Elsevier Inc. All rights reserved.

Regulating Food Intake Hypothalamic centers Appetite center: Promotes feeling of hunger Satiety center: Promotes feeling that we are satisfied or “full” Our body’s regulation of food intake is complex with many factors including: Hormones Neurotransmitters Emotions Environmental cues Food sensations Habits Mechanisms for regulating food intake are still not clearly understood. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Metabolic Rates Basal metabolic rate (BMR) Rate of metabolism when a person is resting but awake, is not digesting food, and is comfortably warm Total metabolic rate (TMR) Total amount of energy (expressed in calories) used by the body per day (Figure 17-5) When the number of your calories in your food intake equals your TMR, your weight remains the same. Copyright © 2016 by Elsevier Inc. All rights reserved.

Basal and Total Metabolic Rates Figure 17-5 shows the factors that determine the basal and total metabolic rates. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Body Temperature Hypothalamus Regulates the homeostasis of body temperature (thermoregulation) through a variety of processes Skin Can cool the body by losing heat from the blood through four processes: radiation, conduction, convection, and evaporation (Figure 17-6) More than 60% of our energy released from nutrient molecules during catabolism is converted to heat rather than being transferred to ATP. When the body is overheated, blood flow to the skin increases. Copyright © 2016 by Elsevier Inc. All rights reserved.

Mechanisms of Heat Loss Figure 17-6 shows the four mechanisms of heat loss. Copyright © 2016 by Elsevier Inc. All rights reserved.

Copyright © 2016 by Elsevier Inc. All rights reserved. Questions? Copyright © 2016 by Elsevier Inc. All rights reserved.