Lesson 1, Topic 1
In Progress

Outline Summary

April 29, 2021

Definitions
A. Nutrition—energy-yielding nutrients, vitamins, and minerals that are ingested and assimilated into the body (Figure 19-1)
B. Metabolism—process of using nutrient molecules as energy sources and as building blocks for our own molecules
C. Catabolism—process that breaks nutrient molecules down, releasing their stored energy; oxygen used in catabolism
D. Anabolism—process that builds nutrient molecules into complex chemical compounds

Metabolic function of the liver
A. Secretes bile to help mechanically digest lipids by emulsifying them
B. Processes blood immediately after it leaves the gastrointestinal tract
1. Helps maintain normal blood glucose concentration
2. Site of protein, carbohydrate, and fat metabolism
3. Removes toxins from the blood
C. Synthesizes several kinds of plasma proteins, including albumins, fibrinogen, clotting factors, etc.
D. Stores useful substances, including glycogen, lipids, certain vitamins

Macronutrients
A. Dietary sources of nutrients
1. Nutrients—food components digested and absorbed by the body
2. Macronutrients—nutrients needed in large daily quantities (carbohydrates, fats, proteins) (Table 19-1)
3. Micronutrients—nutrients needed in tiny daily quantities (vitamins and minerals) (Table 19-3 and Table 19-4)
B. Carbohydrate metabolism
1. Carbohydrates are the preferred energy nutrient of the body
2. Three series of chemical reactions that occur in a precise sequence make up the process of glucose metabolism (Figure 19-2)
a. Glycolysis—occurs in cytoplasm of the cell
(1) Anaerobic process (uses no oxygen)
(2) Changes glucose to pyruvic acid, which is then converted into acetyl CoA
(3) Yields small amount of energy (transferred to ATP)
b. Citric acid cycle (Krebs cycle)—occurs in the mitochondria
(1) Aerobic process (requires oxygen)
(2) Changes acetyl CoA to carbon dioxide
(3) Most energy leaving the citric acid cycle is in the form of high-energy electrons
c. Electron transport system (ETS)—occurs in the mitochondria
(1) Transfers energy from high-energy electrons (from citric acid cycle) to ATP molecules
(2) ATP serves as direct source of energy for cells (Figure 19-3)
3. Adenosine triphosphate (ATP)—energy transferred to ATP differs from energy in nutrient molecules
a. Not stored; released almost instantly
b. Can be used directly to do cellular work

4. Anabolism and storage of glucose
a. Glucose that is not needed immediately for making ATP is stored as glycogen (a long chain of glucose subunits) in liver and muscle cells
b. Glycogenesis—anabolic process of joining glucose molecules together in a chain to form glycogen (storing glucose for later use)
c. Glycogenolysis—catabolic process of breaking apart glycogen chains, releasing individual glucose molecules for use in making ATP
5. Blood glucose level—concentration of glucose in blood
a. Normally maintained between about 80 and 110 mg per 100 mL of blood during fasting
b. Insulin accelerates the movement of glucose out of the blood into cells, therefore decreasing blood glucose and increasing glucose catabolism (Figure 19-4)
C. Fat metabolism
1. Fats (triglycerides) are primarily an energy nutrient
2. Fatty acids and glycerol converted to forms of glucose by gluconeogenesis to be catabolized and energy transferred to ATP (Figure 19-5)
3. Excess fatty acids are anabolized to form triglycerides that are stored in adipose tissue
D. Protein metabolism
1. Proteins are catabolized for energy only after carbohydrate and fat stores are depleted; excess dietary proteins can also be catabolized for energy
2. Gluconeogenesis breaks apart amino acids to convert them to a form that enters the citric acid cycle to produce ATP; the nitrogenous waste product called urea is formed in this process (Figure 19-5)
3. Essential amino acids are those that must be in the diet because the body cannot make them (Table 19-2)

Micronutrients
A. Vitamins
1. Organic molecules that are needed in small amounts for normal metabolism (Table 19-3)
a. May bind to enzymes and coenzymes to help them work effectively
b. Vitamin A has role in vision
c. Vitamin D converts to a hormone that regulates calcium homeostasis
d. Vitamin E is an antioxidant that protects against free radicals
2. Vitamin imbalances
a. Avitaminosis—deficiency of a vitamin
(1) Can lead to severe metabolic problems
(2) Avitaminosis C can lead to scurvy (Figure 19-6)
b. Hypervitaminosis—excess of a vitamin
(1) Can be just as serious as avitaminosis
(2) May be chronic or acute
B. Minerals—inorganic molecules found naturally in the earth
1. Required by the body for normal function, including nerve conduction (Table 19-4)
2. May attach to enzymes to facilitate their work

Regulating food intake
A. Regulatory centers in the hypothalamus play a primary role in controlling food intake
1. Appetite center—produces feelings of hunger
2. Satiety center—produces feelings of satisfaction
B. Food intake regulation results from balance between hypothalamic control centers
C. Many diverse factors influence the hypothalamic control centers (Table 19-5)

Metabolic rates
A. Basal metabolic rate (BMR)—rate of metabolism when a person is lying down but awake, not digesting food, and when the environment is comfortably warm
B. Total metabolic rate (TMR)—the total amounts of energy, expressed in calories, used by the body per day (Figure 19-7)

Metabolic and eating disorders
A. Disruption or imbalance of normal metabolism can be caused by several different factors
1. Inborn errors of metabolism—genetic conditions involving deficient or abnormal metabolic

enzymes
2. Some metabolic disorders are complications of other conditions
a. Hormonal imbalances and eating disorders
B. Eating disorders
1. Anorexia nervosa—characterized by chronic refusal to eat
2. Bulimia—an alternating pattern of craving of food followed by a period of self-denial; in bulimarexia, the self-denial triggers self-induced vomiting
3. Obesity—abnormally high proportion of body fat; may be a symptom of an eating disorder; risk factor for many chronic diseases
4. Protein-calorie malnutrition (PCM)—results from a deficiency of calories in general and proteins in particular; examples are marasmus and kwashiorkor (Figure 19-8 and Table 19-6)

Body temperature
A. Thermoregulation
1. Hypothalamus—regulates the homeostasis of body temperature (thermoregulation) through a variety of processes
2. Blood flow to the skin increases when body is overheated
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3. Heat is lost through the skin by several mechanisms (Figure 19-9)
a. Radiation—flow of heat waves from the blood and skin
b. Conduction—transfer of heat energy to the skin and then to cooler external environment
c. Convection—transfer of heat energy to cooler air that is continually flowing away from the skin
d. Evaporation—absorption of heat from blood and skin by water (sweat) vaporization
4. The body can generate heat to maintain homeostasis over the short term (shivering) or the long term (changes in metabolic rates)
5. Heating and cooling of body is controlled by feedback loops that maintain a stable body temperature (Figure 19-10)
B. Abnormal body temperature can have serious physiological consequences (Figure 19-11)
1. Fever (febrile state)—unusually high body temperature associated with systemic inflammation response
2. Malignant hyperthermia (MH)—inherited condition that causes increased body temperature (hyperthermia) and muscle rigidity when exposed to certain anesthetics
3. Heat exhaustion—results from loss of fluid as the body tries to cool itself; may be accompanied by heat cramps
4. Heatstroke (sunstroke)—overheating of body resulting from failure of thermoregulatory mechanisms in a warm environment
5. Hypothermia—reduced body temperature resulting from failure of thermoregulatory mechanisms in a cold environment
6. Frostbite—local tissue damage caused by extreme cold; may result in necrosis or gangrene