A&P2 CHPT. 23—Nutrition & Metabolism

What are the four mechanisms of heat exchange and how are they defined?

(1) Radiation is the loss of heat as thermal energy. (2) Conduction is the transfer of heat between objects that are in direct contact with each other. (3) Convection is the process of replacing the warm air around the body with cooler air and thus removing body heat. (4) Evaporation cools by removing large amounts of heat as water changes state from liquid to gas.

•Glucose serves as the initial reactant. •occurs in the cytosol of a cell

Glycolysis

Hank, a 17-year-old high school student, suffered a heart attack during a recreational swim. An autopsy revealed that he had had atherosclerosis and that his death had been caused by coronary artery disease. What might have been the cause of this disease that usually strikes a person much older than Hank?

Hank suffered from a genetic disorder known as "familial hypercholesterolemia," a condition in which the LDL receptors are absent or abnormal, the uptake of cholesterol by tissue cells is blocked, and the total concentration of cholesterol and LDLs in the blood is enormously elevated. Victims of the disease usually die in adolescence of coronary artery disease.

Harry is hospitalized with bacterial pneumonia. When you visit him, his teeth are chattering, his skin is cool and clammy to the touch, and he complains of feeling cold, even though the room is quite warm. Explain his symptoms.

Harry's symptoms indicate a fever caused by his bacterial pneumonia. The white cells battling the pneumonia release pyrogens that act directly on the hypothalamus, causing its neurons to release prostaglandins. The prostaglandins reset the hypothalamic thermostat to a higher temperature, causing the body to initiate heat-promoting mechanisms including shivering and vasoconstriction that causes a decline of heat loss from the body surface, cooling of the skin, and shivering.

There are no nutritionally complete proteins. All animal products should be eaten with plant material to make a nutritionally complete protein.

false

Vitamins are inorganic compounds that are essential for growth and good health.

false

When blood glucose levels are low, the body begins to use more noncarbohydrate fuels for energy production. This process is called glucose activation.

false

process that break down complex molecules into simpler ones are anabolic.

false; catabolic

Which of the following nutrients yield the highest amount of energy per gram when metabolized?

fats

When ketone bodies are present in the blood and urine in large amounts, it usually indicates increased metabolism of ________.

fatty acids

Several hours after your last meal, declining blood glucose levels stimulate release of the hormone ________, which stimulates glycogenolysis, lipolysis and fat mobilization, and gluconeogenesis.

glucagon

What is the outcome of ketosis?

glucogenesis

Breakdown of glycogen to release glucose.

gluconeogenesis

The molecule that serves as the major source of readily available fuel for neurons and blood cells is ________.

glucose

Gluconeogenesis is the process in which ________.

glucose is formed from noncarbohydrate molecules

It would not be healthy to eliminate all fats from your diet because they serve a useful purpose in maintaining the body.

true

Peptides called NPY (neuropeptide Y) and AgRP (agouti-related peptides) are powerful appetite enhancers.

true

Heat-loss mechanisms do not include ________.

vasoconstriction of peripheral blood vessels

The amount of protein needed by each person is determined by their age, size, metabolic rate, and the need to build new proteins (whether the body is in positive nitrogen balance).

true

The increased use of noncarbohydrate molecules for energy to conserve glucose is called glucose sparing.

true

The most abundant dietary lipids in the diets of most Americans are triglycerides.

true

The primary function of carbohydrates is energy production within cells.

true

Triglycerides and cholesterol do not circulate freely in the bloodstream.

true

When proteins undergo deamination, the waste substance found in the urine is mostly ________.

urea

The major role of high-density lipoproteins (HDLs) is to store energy in the form of fat.

false

The preferred energy fuel for the brain is fat.

false

In order for amino acids to be oxidized for energy, the amine group (NH2) must be removed.

true

Your car breaks down along the highway on a cold winter afternoon. As you wait for help to arrive, the temperature drops significantly inside the car. Describe two involuntary adjustments an adult body will make in order to maintain core body temperature.

1. Constriction of cutaneous blood vessels: Sympathetic fibers cause vasoconstriction of the blood vessels in skin in order to reduce heat otherwise lost through radiation from the skin. 2. Shivering: Brain centers controlling muscle tone are activated which eventually cause heat generation from the involuntary contraction of skeletal muscles.

Which of the choices below happens during the absorptive state?

Anabolic processes exceed catabolic ones.

Which of the following is correct?

Each FADH2 yields about 1.5 ATP via oxidative phosphorylation.

cellular respiration is an anabolic process

False; catabolic

Megadoses of vitamin supplements may have serious consequences. Extreme excess of which vitamin group, water or fat soluble, is most likely to cause serious health problems, and why?

Fat-soluble vitamins are most likely to cause serious health problem such as damage to the brain, kidneys, liver, bone, and cardiovascular system, because they are stored in the body and excesses are not removed.

After chopping wood for about 2 hours on a hot but breezy afternoon, John stumbled into the house and immediately fainted. His T-shirt was wringing wet with perspiration, and his pulse was faint and rapid. What is your tentative diagnosis? Explain your reasoning and note what you should do to help John's recovery.

John was suffering from heat exhaustion due to excessive loss of body fluids (indicated by his wet T-shirt); his low blood pressure; and cool, clammy skin. To help his recovery, he should be given fluid and electrolyte replacement therapy and should be cooled down.

The patient is a 28-year-old female with type-1 diabetes mellitus. She developed viral gastroenteritis with nausea and vomiting. She did not take her insulin and she became increasingly nonresponsive. Her husband called 911 and she was taken to the emergency room. Her pulse rate was 128 and her respiratory rate was 28, deep, and smelled fruity (Kussmaul breathing). Her urinary glucose and ketone levels were both 4+. Her pH was dangerously low. Explain how the body attempted to compensate for the low serum pH.

Ketosis leads to metabolic acidosis. The deep, rapid respirations were the body's attempt to compensate for the extremely low pH by blowing off CO2, resulting in less carbonic acid that in turn caused pH to rise.

The patient is 45 years old and is obese. He states he has been on the Atkins diet (low carbohydrate and high protein and fat) and has lost 20 pounds. What are the dangers inherent in following fad diets for quick weight loss?

Many fad diets are nutritionally unhealthy, particularly if they limit certain groups of nutrients. Some of the liquid high-protein diets contain poor-quality protein and are actually dangerous.

The term essential nutrient refers to the chemicals that can be interconverted in the liver so that the body can maintain life and good health.

false

What is the significance of the fact that monosaccharides are phosphorylated immediately upon entry into cells?

Monosaccharides are phosphorylated immediately upon entry into cells so that entry into metabolic pathways is possible. Additionally, phosphorylation, to change the structure of glucose, allows the maintenance of a diffusion gradient for simple glucose. Phosphorylation also prevents glucose from leaving the cell.

Define nitrogen balance. List three factors that might lead to negative nitrogen balance and three that might result in positive nitrogen balance.

Nitrogen balance is a state when the amount of nitrogen ingested in proteins equals the amount of nitrogen excreted in urine and feces. Factors leading to negative nitrogen balance (when protein breakdown exceeds the use of protein for building structural or functional molecules) include: physical and emotional stress, poor-quality dietary protein, and starvation. Factors leading to positive nitrogen balance (when the rate of protein synthesis is higher than the rate of its breakdown and loss) include: the normal condition in growing children and pregnant women, periods of rebuilding or repair following illness, and site-specific regeneration following injury.

What are four possible complications of obesity from a medical standpoint?

Obesity contributes to insulin resistance and type 2 diabetes mellitus; the obese also have a higher incidence of atherosclerosis, hypertension, heart disease, and osteoarthritis.

What is obesity, and what health problems accompany or follow its onset?

Obesity is a BMI (body mass index) greater than 30. Health problems accompanying or following obesity include a higher incidence of arteriosclerosis, hypertension, coronary artery disease, and diabetes mellitus.

Which of the following best defines negative nitrogen balance?

Protein breakdown exceeds protein synthesis.

Select the correct statement about proteins.

Proteins will be used by most cells for ATP synthesis if insufficient carbohydrates are ingested.

A friend expresses concern that their family hardly ever consumes fruits and vegetables and is not eating healthy. Use the USDA's MyPlate food guide to help your friend understand how to improve this family's diet.

The USDA's guidelines are represented by a dinner plate that suggests how to plan meals relative to amounts and varieties of foods from each group. The plate depicts approximately 30% grains, 30% vegetables, 20% fruits, and 20% protein. A cup nearby represents dairy. The plate illustrates that half of your foods should be fruits and vegetables. Many people consume less than this recommended amount.

Define amino acid pool and explain how the pool is maintained even though we excrete amino acids daily.

The amino acid pool consists of the body's total supply of free amino acids needed to resynthesize body proteins. Even though a small amount of amino acids and proteins is lost daily in urine, these are replaced through diet. If they are not replaced, the amino acids resulting from tissue breakdown become a part of the pool.

Which of the following statements is FALSE?

The amino acid pool is the body's total supply of amino acids in the body's proteins.

The patient is 52 years old and has a history of hypertension. His cholesterol level is 245. He states his job is very stressful and he is recently going through a divorce. He admits to being overweight and has an inactive lifestyle. His father died of a stroke at age 60. He is worried about having a heart attack and/or stroke and wishes to change his lifestyle. Among other advice, the nurse encourages the patient to eat more cold-water fish such as salmon. Explain why eating more fish would be of benefit for this patient.

The omega-3 fatty acids in cold-water fish lower the proportions of both saturated fats and cholesterol, make blood platelets less sticky, thus helping to prevent spontaneous clotting that can block blood vessels and they also appear to lower blood pressure.

How is the postabsorptive state controlled and initiated?

The postabsorptive state is controlled by the interaction of the sympathetic nervous system and several hormones, especially glucagon. The trigger for initiating postabsorptive events is damping of insulin release, which occurs as blood glucose levels begin to drop. Insulin levels decline, and the insulin-induced cellular responses are inhibited.

The primary function of cellular respiration is to ________.

break down food molecules and generate ATP

Explain what happens to pyruvic acid if oxygen is not present in sufficient quantities to support the electron transport system.

When oxygen is not present in sufficient amounts, the NADH + H+ produced during glycolysis begins to unload its hydrogen "baggage" back onto pyruvic acid, reducing it. This addition of hydrogen atoms to pyruvic acid results in the production of lactic acid.

Which of the choices below is not a source of blood glucose during the postabsorptive state?

absorption of glucose from the GI tract

Glycogen is formed in the liver during the ________.

absorptive state

In the liver, the amine group of glutamic acid is removed as ________ in the oxidative state.

ammonia

Conversion of fatty acids into acetyl groups.

beta oxidation

As the body progresses from the absorptive to the post absorptive state, the ________ continues to burn glucose while virtually every other organ in the body switches to fatty acids as its major energy source.

brain

The body is considered to be in nitrogen balance when the amount of nitrogen ingested in lipids equals the amount excreted in urine.

false

Catabolism would be best described as a process that ________.

breaks down complex structures to simpler ones

Lipogenesis occurs when ________.

cellular ATP and glucose levels are high

involves the removal of hydrogen electrons and CO2 from the substrate molecule

citric acids (krebs) cycle

Heat transfer into the chair you are sitting on.

conduction

Prostaglandins play a role in ________.

control of blood pressure

Heat exchange when you are under a ceiling fan.

convection

Glycolysis is best defined as a catabolic reaction based upon the ________.

conversion of glucose into two molecules of pyruvic acid

Which of the choices below is NOT a fate of carbohydrate taken into the body?

direct conversion into a nucleic acid

Which of the following food groups are considered good sources of complete proteins?

eggs, milk, yogurt, meat, and fish

•produces the most ATP •involves the use of oxygen to pick up excess hydrogen and electrons

electron transport chain

The term basal metabolic rate reflects the ________.

energy the body needs to perform only its most essential activities

heat loss during sweating

evaporation

Conditions that promote the oxidative deamination and energy use of amino acids include ________.

excessive amounts of protein in the diet

Beta oxidation is the initial phase of fatty acid oxidation, and it occurs in the cytoplasm.

false

Diets high in cholesterol and saturated fats tend to produce high HDL concentrations.

false

Except for lactose and some glycogen, the carbohydrates we ingest are mainly from animals.

false

Glycogen accounts for 80-85% of stored energy in the body.

false

In gluconeogenesis, during the post-absorptive state, amino acids and ________ are converted to glucose.

glycerol

Storage of glucose in the form of glycogen.

glycogenesis

Which term describes the action of an endurance runner the night before the race as she "carbo-loads" when eating a large pasta dinner?

glycogenesis

Formation of glucose from proteins or fats.

glycogenolysis

Glucose can be obtained from ________.

glycogenolysis

Breakdown of glucose to pyruvic acid.

glycolysis

Red blood cells lack mitochondria. As a result, ATP production is solely through ________.

glycolysis

Which of the following does not occur in the mitochondria?

glycolysis

Which of the choices below describes the pathway of cellular respiration (the complete oxidation of glucose)?

glycolysis, citric acid (Krebs) cycle, electron transport chain, oxidative phosphorylation

The ________ acts as the body's thermostat.

hypothalamus

Which of the following is the major role of leptin in the body?

increase appetite and food intake

Which hormone directs essentially all the events of the absorptive state?

insulin

While traveling abroad in Africa you observe a large number of people with goiter (enlarged thyroid). Which mineral deficiency could be responsible for this?

iodine

Minerals required by the body in moderate amounts include all of the following EXCEPT ________.

iron and selenium

Cholesterol, though it is not an energy molecule, has importance in the body because it ________.

is a stabilizing component of the plasma membranes and is the parent molecule of steroid hormones

Which of the following is not true of beta oxidation?

it involves anabolism of fats

Formation of ketone bodies.

ketogenesis

Anabolism includes reactions in which ________.

larger molecules or structures are built from smaller ones

Synthesis of lipids from glucose or amino acids.

lipogenesis

Splitting of triglycerides into glycerol and fatty acids.

lipolysis

The process of breaking triglycerides down into glycerol and fatty acids is known as ________.

lipolysis

Oxidative deamination takes place in the ________.

liver

Oxidation reduction reactions ________.

may involve the loss of hydrogen and electrons

It is important to ensure that your diet is adequately rich in vitamins because ________.

most vitamins are coenzymes needed to help the body utilize essential nutrients

Glycogenesis begins when ATP levels are high, and glucose entering cells is phosphorylated to glucose-6-phosphate and converted to its isomer, glucose-1-phosphate.

true

High levels of HDLs are considered good.

true

Which of the following statements best describes complete protein?

must contain all the body's amino acid requirements for tissue maintenance and growth

Which of the following mechanisms produces the most ATP during cellular respiration?

oxidative phosphorylation

What process primes a molecule to change in a way that increases its activity, produces motion, or does work?

phosphorylation

Which of the following is a source of complex carbohydrates?

potatoes

In the case of a person who consumes a normal, balanced diet, proteins are essential to the body for all of the following EXCEPT ________.

production of energy

The ingestion of which nutrient type results in the greatest food-induced thermogenesis?

proteins

At the conclusion of glycolysis, most of glucose's chemical energy is found in the ________.

pyruvic acid molecules

Heat loss in the form of infrared waves.

radiation

Which of the following is a normal consequence of the activation of the heat-promoting center?

release epinephrine

When blood is cooler than the hypothalamic set point, the person may ________.

shiver

Which of the choices below is not a mechanism of heat transfer used by the body?

shivering

A recent health screening revealed a low-density-lipoprotein (LDL) level over 130. Which of the following should be prescribed?

statins

Which of the choices below is not a mechanism of heat production?

sweating

Which of the following is not an important function of the liver?

synthesis of vitamin K

Many factors influence basal metabolic rate (BMR). What is the most critical factor?

the ratio of surface area to volume (weight) of the body

The term metabolism is best defined as ________.

the sum of all biochemical reactions in the body

The amount of ________ produced is probably the most important hormonal factor in determining basal metabolic rate (BMR).

thyroxine

Transamination is the process whereby the amine group of an amino acid is ________.

transferred to a keto acid

Which of the following is not a function of low-density-lipoproteins (LDLs)?

transport cholesterol from the peripheral tissues to the liver

The most abundant dietary lipids are ________.

triglycerides

Carbohydrate and fat pools are oxidized directly to produce cellular energy, but amino acid pools must first be converted to a carbohydrate intermediate before being sent through cellular respiration pathways.

true

For use as fuel, all food carbohydrates are eventually transformed to glucose.

true

Ghrelin, produced by the stomach, is a powerful appetite stimulant.

true

In India, rice is a large part of the diet. Lack of which vitamin in rice would lead to higher levels of blindness in this population?

vitamin A