Chapter 16 - Regulation of Organic Metabolism and Energy Balance

Familial hypercholesterolemia results from a genetic mutation that produces insufficient or nonfunctional receptors for A) Chylomicrons B) VLDL This is the correct answer. C) LDL D) HDL

A mutation in the gene that codes for LDL receptors results in decreased numbers or nonfunctional LDL receptors. Thus, LDL is not adequately removed from the blood leading to high blood levels of cholesterol (hypercholesterolemia).

Which of the following is NOT a source of the fatty acids that compose triglycerides in adipose tissue? This is the correct answer. A) Amino acids that adipose cells directly convert to fatty acids B) Glucose that adipose cells directly convert to fatty acids C) VLDL which contains triglycerides that were synthesized from glucose by the liver D) Chylomicrons that contain triglycerides that were synthesized from fatty acids by intestinal epithelial cells.

Adipose cells do not readily convert amino acids to fatty acids. Although this process can occur in the liver, the overwhelming majority of fatty acids produced by the liver are derived from glucose. These fatty acids are then packaged with proteins for form VLDL which enters the blood. The enzyme lipoprotein lipase removes fatty acids from the VLDL, and those fatty acids then enter adipose cells where they can be stored as triglycerides. Likewise, fatty acids can be removed from chylomicrons, and they enter adipose cells for storage as triglycerides.

Which of the following is NOT a long-term consequence of untreated diabetes? This is the correct answer. A) Osteoporosis B) Heart disease C) Blindness D) Kidney disorders leading to kidney failure E) Peripheral neuropathy

All of the diseases listed above, except osteoporosis, can occur if diabetes mellitus is not controlled properly. Osteoporosis is a disease of demineralization (loss of calcium) of bone that occurs mostly in older people and is the reason for high incidence of fractures of the hip and leg bone in old age. Prolonged, untreated hyperglycemia results in damage to small blood vessels. As a result, there is a decreased availability of oxygen and nutrients to tissues such as kidney, retina, and nerves. Diabetes is also a major risk factor for developing heart disease (coronary artery disease).

A human physiology student has been learning about diabetes and its symptoms. She was presented with a case of an obese, middle-aged patient, just very recently diagnosed with type II diabetes mellitus. Which of the following symptoms would the student NOT expect to see listed in her case study of this patient? A) Hyperglycemia B) Glucose present in the urine C) Insulin resistance This is the correct answer. D) Inability to produce insulin E) Excessive urine production

Although some individuals with type 2 diabetes mellitus may produce reduced amounts of insulin due to an impared response of the pancreatic beta cells to hyperglycemia, the inability to produce insulin is a hallmark of type I diabetes mellitus where the beta cells are damaged due to an autoimmune reaction. In type 2 diabetes insulin is generally present in the plasma. However, insulin is not effective on its target tissue due to the development of insulin resistance. This may be due to problems with insulin receptors or glucose transporters. As a result of insulin resistance, glucose entry to target tissues is diminished leading to hyperglycemia. This condition leads to increased loss of glucose in the urine (glycosuria) accompanied by increased loss of water in the urine (polyuria).

Which of the following statements concerning basal metabolic rate (BMR) is NOT correct? A) BMR is measured at least 12 hours after eating and while the subject is at rest This is the correct answer. B) BMR increases with age, thus elderly people should eat more frequently C) An increase in thyroid hormone secretion increases BMR D) BMR can be thought of as the energy required for maintenance of the heart, brain, kidneys, and liver

BMR decreases with age. All other statements regarding BMR are correct.

Which of the following is NOT a target of the hormone insulin? A) Muscle tissue This is the correct answer. B) Brain tissue C) Adipose tissue D) Liver

Brain tissue is not a target of pancreatic insulin since the hormone does not cross the blood-brain barrier and the glucose transporter is not insulin sensitive. In other cells insulin promotes insertion of glucose transports in the cell membrane. The most important targets of insulin are muscle and adipose tissues. Liver is also an important target of insulin. In the liver insulin is not required for glucose entry into the cells but rather for the metabolic events that follow glucose entry.

Cortisol is a hormone secreted in higher amounts as a response to stress. Which of the following pairs of terms best describes a major target and action of this hormone, respectively? A) Bone; mineralization B) Muscle; vasodilation This is the correct answer. C) Liver; gluconeogenesis D) Hypothalamus; TRH release E) Brain; fatty acid metabolism

Cortisol increases formation of newly formed glucose in the liver through "gluconeogenesis". Gluconeogenesis occurs when amino acids are converted to glucose when dietary ingestion of carbohydrates is low. Cortisol enhances formation of the enzymes which carry out gluconeogenesis. In high amounts cortisol actually causes demineralization of bone, not mineralization. Vasodilation of muscle during stress and physical activity is caused by adrenal medullary hormones, not cortisol. Adrenal medulla hormones are the ones that activate the brain and cause arousal, not cortisol. While cortisol has action on the hypothalamus, it tends to decrease CRH release and not affect TRH release. The central nervous system does not metabolize fatty acids.

Which of the following mechanisms of heat transfer can only result in heat loss from the body? This is the correct answer. A) Evaporation B) Conduction C) Convection D) Radiation

Evaporation is a mechanism of heat loss only. All other mechanisms of heat transfer can result in heat loss or gain.

Which of the following would NOT lead to satiety? A) Increased insulin levels B) Increased body temperature This is the correct answer. C) Increased secretion of ghrelin D) Increased stretch initiated by food within the gastrointestinal tract

Ghrelin, a hormone produced by the stomach, increases appetite. After eating, stretch within the GI tract, increased insulin, and the increase in body temperature that accompanies the increase in MR due to food-induced thermogenesis are all believed to act as satiety factors.

Glucagon A) Is secreted by the beta cells of the pancreatic islets This is the correct answer. B) Is secreted in response to a decrease plasma glucose concentration C) Is an agonist of insulin D) Increases fat stores by inhibiting the enzyme that catalyzes breakdown of triglycerides

Glucagon is secreted in response to a decrease plasma glucose concentration, an event that usually occurs in the postabsorptive state, a few hours after a meal. Glucagon is a peptide hormone produced by alpha cells of the pancreatic islets, not the beta cells. Glucagon acts to promote glucose production and decrease glucose storage. Glucagon action is antagonistic to insulin. It acts on the liver to stimulate glycogenolysis, producing glucose and releasing it into the blood. Glucagon has no known major effect on fat metabolism.

Which of the following events is NOT characteristic of the postabsorptive state? A) Breakdown of glycogen by the liver B) Synthesis of glucose by the liver C) Breakdown of triglycerides by adipose cells D) Breakdown of protein to release amino acids This is the correct answer. E) Production of glycogen by the skeletal muscle cells

Glycogenolysis, not glycogen production, would be expected to occur in skeletal muscle cells in the postabsorptive state. The liver produces glucose by breaking down glycogen and by converting other substrates such as lactate, glycerol, and amino acids to glucose. The glycerol used for this process comes from the breakdown of triglycerides by adipose cells, and the amino acids come from the breakdown of proteins in various cells. The breakdown of proteins to supply amino acids is more limited, and is not the major source of glucose produced by the liver.

The lipoproteins that remove cholesterol from cells and deliver it to the liver for processing are A) VLDL B) Chylomicrons C) LDL This is the correct answer. D) HDL

HDL (high density lipoprotein) removes excess cholesterol from tissues and delivers it to the liver. LDL (low density lipoprotein) delivers cholesterol to various body cells. Chylomicrons are produced from lipids absorbed by intestinal epithelial cells. VLDL primarily delivers fatty acids to adipose cells.

Epinephrine and sympathetic nervous stimulation This is the correct answer. A) Inhibit insulin secretion B) Inhibit glucagon secretion C) Inhibit glycogenolysis in liver and skeletal muscle D) Inhibit lipolysis

Increasing sympathetic nervous system activity inhibits insulin secretion and stimulates glucagon secretion. It promotes gluconeogenesis in the liver and glycogenolysis in the liver and skeletal muscle cells. It stimulates also stimulates lipolysis in the adipose tissues.

Insulin A) Facilitates the transport of glucose into most brain cells B) Increases blood glucose levels to assure adequate nourishment for the brain This is the correct answer. C) Promotes fat storage in the body D) Secretion is stimulated by a lowered blood glucose level

Insulin promotes glucose uptake into most tissues, but not the brain cells. By increasing glucose uptake into fat cells, insulin promotes fat synthesis and storage. Insulin inhibits the enzyme that catalyzes the hormone-sensitive lipase of the fat cells which helps breakdown triglycerides to fatty acids and monoglycerides. Insulin is a hormone that acts to decrease blood sugar levels. The primary stimulus for insulin secretion is an increase in blood glucose level; low blood glucose level inhibits insulin release.

Which of the following is NOT a characteristic of the calorigenic effect typical of hyperthyroidism? This is the correct answer. A) Intolerance to cold B) Weight loss C) Excessive sweating D) Increased hunger

Intolerance to cold is a characteristic of hypothyroidism, not hyperthyroidism. Hyperthyroidism increases the BMR leading to excessive hunger, weight loss, increased body temperature, excessive sweating, and intolerance to a warm environment.

Which of the following is NOT a stimulus for pancreatic beta cell secretion of insulin? A) Glucose-dependent insulinotropic peptide (GIP) B) An increase in the plasma glucose concentration C) An increase in the plasma amino acid concentration This is the correct answer. D) An increase in sympathetic stimulation

It is the parasympathetic system, not the sympathetic system that stimulates pancreatic beta cell secretion of insulin. Sympathetic stimulation inhibits insulin secretion. Beta cells in the pancreas also secrete insulin in response to increased plasma levels of glucose, amino acids, and GIP (one of the incretins).

During the absorptive state, which of the following is a product of amino acid deamination and serves as a source of energy for liver cell functions in the absorptive state? This is the correct answer. A) Keto acids B) Ketone bodies C) Lactic acid D) Glucose

Keto acids are a product of deamination of amino acids. Keto acids enter the Krebs tricarboxcylic acid cycle and are catabolized to provide energy for the liver cells in the absorptive state. Ketone bodies are derived from fatty acid metabolism and provide an important energy source during prolonged fasting. Lactic acid is a product of anaerobic cellular respiration. Glucose from intestinal absorption entering liver cells is primarily used for storage, in the form of glycogen. Besides being converted to glycogen, glucose can also be metabolized to alpha-glycerol phosphate, or used for synthesis of fatty acids which are then used to form triglycerides.

Maintenance of body temperature in newborns is aided by A) Brown adipose tissue B) An uncoupler protein that increases heat production during metabolism C) An increased ability to shiver D) Brown adipose tissue and an increased ability to shiver This is the correct answer. E) Brown adipose tissue and an uncoupler protein that increases heat production during metabolism

Newborns possess brown adipose tissue rich in mitochondria that contain an uncoupler protein. This uncoupler protein allows the energy derived from metabolizing food to be converted to heat instead of ATP. The shivering mechanism is not fully developed in newborns.

Cortisol A) Is produced by the adrenal medulla This is the correct answer. B) Concentrations in the plasma will increase during stress C) Has effects similar to those of insulin D) Reduces cell sensitivity to glucagon during fasting

Plasma concentrations of cortisol increase during exposure to a variety of stressors such as infections, injuries or psychological stress. Cortisol is not produced in the adrenal medulla but rather in the adrenal cortex. The adrenal medulla produces the catecholamines such as epinephrine and norepinephrine. Cortisol has effects opposite to that of insulin. For example, cortisol tends to increase glucose levels in the blood while insulin tends to decrease glucose levels in the blood. Cortisol reduces muscle and adipose cell sensitivity to insulin, not to glucagon.

During a prolonged postabsorptive state, such as during a fast, the need for protein breakdown is reduced when _______ are released into the blood by the liver. A) Glucose molecules This is the correct answer. B) Ketones C) Glycogen molecules D) VLDL

The liver converts fatty acids into ketones which enter the blood and may be used as an energy source by many tissues including neural tissue. Glycogen is never released by the liver cells into the blood; it is first converted to glucose via glycogenolysis. VLDL are only produced and released by the liver during the absorptive state. While glucose is released into the blood by liver cells during the postabsorptive state, fatty acids and amino acids are used in the process of gluconeogenesis to synthesize this glucose. The need for protein breakdown is not reduced as a result of gluconeogenesis.

Which of the following IS a means of glucose processing in the liver during the absorptive state? A) Glucose is converted to glycogen molecules which enter the blood and are stored in adipose tissue B) Glucose is converted to triglycerides which enter the blood and are stored in skeletal muscle tissue This is the correct answer. C) Glucose is converted to lipoproteins which enter the blood and are stored in adipose tissue D) Glucose is converted to chylomicrons which enter the blood and are stored in adipose tissue

The liver converts glucose to triglycerides which are packaged with proteins to form lipoproteins. These very low density lipoproteins (VLDL) enter the blood, and they deliver fatty acids to adipose cells. The liver is capable of converting glucose to glycogen and triglycerides, but these are stored in the liver. Chylomicrons are not synthesized by the liver; they are produced by intestinal epithelial cells.

The two most important controls of the absorptive and postabsorptive states are This is the correct answer. A) Insulin and glucagon B) Insulin and cortisol C) Cortisol and glucagon D) Insulin and epinephrine

The pancreatic hormones insulin and glucagon play the most important role in regulating the absorptive and postabsorptive states. The adrenal hormones cortisol and epinephrine are also important, but their roles can be considererd secondary to insulin and glucagon.

Which of the following is NOT an effect of adrenal medullary hormone epinephrine? A) Increased glycogenolysis in the liver B) Dilation of pulmonary bronchioles This is the correct answer. C) Decreased heart rate D) Increased basal metabolic rate

The release of the adrenal medulla hormone, epinephrine, is stimulated by the sympathetic system. Epinephrine will increase not decrease heart rate as well as heart contractility. Epinephrine will also stimulate the liver cells to increase breakdown of glycogen to glucose (glycogenolysis), leading to glucose release. It will also lead to dilation of small pulmonary airducts (bronchioles)resulting in an increase in delivery of oxygen and nutrients to tissues during times of physical stress (e.g., fight or flight, exercise). Epinephrine will also stimulate metabolism leading to increased basal metabolic rate (BMR).

The lower insulin levels that are typically seen during exercise result in decreased glucose uptake by skeletal muscle cells.

This statement is false. Although the mechanism is not understood, skeletal muscle contraction stimulates insertion of glucose transporters. Thus, glucose uptake is higher in an active skeletal muscle cells than in inactive muscle cells, independent of the insulin concentration.

The metabolic profile of an exercising person is most like the metabolic profile of a person in the absorptive state.

This statement is false. During exercise there is an increase in glucose production by the liver, fatty acid breakdown by adipose cells, and an increase in fatty acid utilization by most cells. This is typical of a postabsorptive state.

During the absorptive state the liver and skeletal muscles store amino acids as protein so that they will be available during the postabsorptive state.

This statement is false. During the absorptive state amino acids may be used to synthesize proteins; however, these proteins are necessary for normal cell function and growth and do not serve as a source of energy in the postabsorptive state. Most excess amino acids acquired during the absorptive state are converted to carbohydrate or fat.

Scientists have found that most obese individuals suffer from a deficit in the hormone leptin. The reduced availability of leptin lowers the normal effect on the hypothalamus to reduce food intake.

This statement is false. Leptin levels are usually normal in obese individuals. However, they may suffer from an inability to bind and respond to leptin in the hypothalamus.

The time period when ingested nutrients are entering the blood from the gastrointestinal tract is called the postabsorptive state.

This statement is false. This time period is called the absorptive state, as many nutrients are being absorbed into the blood. During the postabsorptive state the body's own nutrient stores must supply energy.

The primary goal of glucose sparing is to provide sufficient glucose for the brain, thus many other body cells rely on fats for energy.

This statement is true. The primary fuel source used by the brain is glucose. During the postabsorptive state tissues other than the brain utilize fatty acids for energy, and the liver produces glucose by breaking down glycogen to glucose and converting other substrates to glucose via gluconeogenesis. The adipose tissue breaks down triglycerides to glycerol and fatty acids. The fatty acids are used by cells (other than the neural tissue) as a source of energy. The glycerol can be used by the liver for gluconeogenesis and the fatty acids can be further broken down by the liver to produse ketones. Ketones can be used by many cells of the body, including neuronal tissue as a source of energy. These processes make up the "glucose sparing" that keeps blood glucose levels sufficient to support the nervous system.

Which of the following does NOT characterize type 1 diabetes mellitus? This is the correct answer. A) Increased glucose utilization due to excessive glucose availability B) Excessive urination due to the osmotic effect of glucose in the urine C) Acidosis due to excessive levels of ketones (ketone bodies) in the plasma D) Dehydration E) Hyperglycemia

Type I diabetes mellitus is characterized by elevated glucose levels in the plasma but not increased glucose utilization. In type I diabetes mellitus insulin is absent or markedly decreased in amount. As a result, there is no stimulus or a reduced stimulus for insertion of glucose transporters in cell membranes. Since glucose cannot effectively enter the target cells, glucose concentration in the plasma is higher than normal (hyperglycemia). Dehydration can occur due to excessive urination. Glucose in the urine (glycosuria) tends to increase water excretion by osmosis. There is often acidosis due to excessive levels of ketones (ketone bodies) such as acetoacetic acid and acetone in the plasma. Insulin would normally suppress lipolysis and ketone formation.