Chapter 26 (Nutrients & Metabolism) Study Guide

Question 1

1) What is the key factor that determines body weight?
2) How do you gain weight?
3) How do you lose weight?

Answer 1

1) Determined by the body’s energy balance: If energy intake and output are equal, body weight is stable
2) Gain weight if intake exceeds output
3) Lose weight if output exceeds intake

Question 2

1) What percent of body weight variation is hereditary?
2) What two main environment factors make up the rest of the variation?

Answer 2

1) 30% to 50% of variation in human weight is hereditary
2) Eating and exercise habits account for the rest of the variation

Question 3

1) What are gut-brain peptides?
2) What is the purpose of short term regulators of appetite?
3) Give 2 examples of short term regulators

Answer 3

1) Act as chemical signals from the gastrointestinal tract to the brain, influence appetite
2) Makes one feel hungry and begin eating and makes one feel satiated and end a meal
3) Ghrelin and cholecystokinin (CCK)

Question 4

1) What cells secrete ghrelin?
2) Is ghrelin a short term or long term regulator of appetite?
3) After ghrelin has been released, what organ is stimulated in response to release of ghrelin? What hormone does that organ secrete and why?

Answer 4

1) Parietal cells in the fundus of an empty stomach
2) Short-term regulator
3) Stimulates hypothalamus to release growth-hormone releasing hormone (GhRH) to prime the body to take advantage of the nutrients about to be absorbed.

Question 5

1) What cells secrete cholecystokinin (CCK)?
2) Is CCK a short term or long term regulator of appetite? 3) After CCK has been released, what does it cause secretion of?
4) What fibers does CCK stimulate?
5) What is the overall goal of CCK in response to appetite?

Answer 5

1) Enteroendocrine cells of the duodenum and jejunum
2) Short-term regulator
3) Stimulates secretion of bile and pancreatic enzymes
4) Sensory fibers of vagus nerve and the brain, suppressing appetite
5) Acts as a signal to stop eating

Question 6

1) What is the purpose of long term regulators of appetite?
2) What are the two long term regulators of appetite? What is their overall goal, i.e., what do they help with?
3) What cells in the body secrete these long term regulators of appetite?

Answer 6

1) To govern caloric intake and energy expenditure over periods of weeks to years
2) Leptin and insulin inform the brain of how much adipose the body has, and activate mechanisms for adding or reducing fat
3) Leptin is secreted by adipocytes, insulin is secreted by beta pancreatic cells

Question 7

Does gastric peristalsis stimulate or inhibit hunger?

Answer 7

Stimulate hunger

Question 8

1) What are some causes of obesity?
2) What impact does this have on physical health and life expectancy?

Answer 8

1) Causes are diverse: heredity, overfeeding in infancy and childhood; evolution resulted in adaptations to store nutrients to cope with times of scarcity
2) Shortens life expectancy; increased risk of atherosclerosis, hypertension, diabetes mellitus, joint pain, kidney stones and gallstones, cancer of uterus, breast, and prostate, and sleep apnea

Question 9

1) Can you define nutrient?
2) Name the 6 categories of nutrients. Include which are macronutrients and which are micronutrients.
3) Can you explain the difference between macronutrient and micronutrient?

Answer 9

1) Any ingested chemical used for growth, repair, or maintenance of the body
2) Water, carbohydrates, lipids, and proteins (macronutrients) and vitamins and minerals (micronutrients)
3) Macronutrients means we require large quantities; micronutrients means only small amounts are needed

Question 10

1) Can you define/explain recommended daily allowance (RDA)?
2) Define essential nutrient.
3) Give examples of essential nutrients.

Answer 10

1) RDA: The safe estimate of daily intake that would meet the nutritional needs of most healthy people
2) Essential nutrients: Cannot be synthesized by the body
3) Minerals, most vitamins, eight amino acids, and one to three of the fatty acids must be consumed in diet

Question 11

1) What two hormones regulate blood glucose levels, maintain proper balance between glucose and glycogen? 2) What gets used as fuel when low on glycogen and glucose?
3) Excess carbohydrate are converted to what organic substance?

Answer 11

1) Insulin and glucagon
2) Fats used as fuel when glucose and glycogen levels are low
3) Into fats

Question 12

1) Why does the body need dietary fiber?
2) Where do we get this dietary fiber?
3) Does the human body digest fiber?

Answer 12

1) Decreases blood cholesterol and LDL levels; absorbs water in intestines, softens stool and increases its bulk, stretches colon, and stimulates peristalsis thereby quickening passage of feces
2) Cellulose, chitin (animal origin), pectin, gums, and lignins
3) Fiber is not digested

Question 13

1) What is the purpose of fat?
2) What is glucose-sparing and protein-sparing?
3) What are some fat soluble vitamins? What do they depend on in order to be absorbed?
4) Which fat soluble vitamins are produced by gut bacteria?

Answer 13

1) Fat has glucose-sparing and protein-sparing effects when used for energy needs, and fat-soluble vitamins can only be absorbed with dietary fat
2) Fat is
3) A, D, E, K require fat to be absorbed
4) Vitamin K

Question 14

1) How are lipids transported in the plasma?
2) What are high levels of LDL suggestive of?
3) What are high levels of HDL suggestive of?
4) Should the ratio of HDL to LDL be higher or lower and how are some ways this can be achieved?

Answer 14

1) Lipoproteins (like chylomicrons) transport lipids
2) High LDL levels: suggests cholesterol deposition in arteries
3) High level of HDL: indicates that cholesterol is being removed from arteries and transported to the liver for disposal; is beneficial
4) Higher HDL than LDL; regular aerobic exercise, avoid smoking, saturated fats, coffee, stress (all raise LDL levels)

Question 15

1) When would dietary consumption of protein need to be increased?
2) What happens if excessive amounts of proteins are consumed?

Answer 15

1) Higher intake recommended under conditions of stress, infection, injury, and pregnancy
2) Excessive intake overloads the kidneys with nitrogenous waste and can cause kidney damage

Question 16

1) In terms of proteins what is the difference between essential amino acids and inessential amino acids?
2) Do cells store surplus amino acids?
3) Can you synthesize a protein if you are only missing one amino acid?

Answer 16

1) Essential amino acids are not synthesized by the body, inessential ones are.
2) Cells do not store surplus amino acids for later use
3) When a protein is synthesized, all amino acids must be present at once; if one is missing, the protein cannot be synthesized

Question 17

1) What are minerals?
2) What are vitamins?
3) Are these organic or inorganic? Are they used as fuel?

Answer 17

1) Minerals: inorganic elements that plants extract from soil or water and introduce into the food web
2) Vitamins: organic small dietary compounds that are necessary for metabolism
3) Neither is used as fuel, but both are essential to our ability to use other nutrients

Question 18

1) What percentage of body mass is minerals?
2) What are the two major minerals and their functions? 3) Phosphorus is also a key structural component of what?
4) Why does the body need iron?

Answer 18

1) Minerals constitute about 4% of the body mass
2) Calcium and phosphorus in bones and teeth. Phosphorus: Basis of the phosphate buffer system.
3) Key structural component of phospholipids, ATP, cAMP, GTP, and creatine phosphate
4) Iron is needed for the oxygen-carrying capacity of hemoglobin and myoglobin

Question 19

1) Water-soluble vitamins are absorbed with ________ in the small intestine. Are excess water-soluble vitamins stored in the body?
2) What is the function of vitamin C (ascorbic acid)?
3) What is the function of B12 and what is needed for its absorption?

Answer 19

1) Absorbed with water in small intestine and quickly excreted by kidneys, not stored
2) Vitamin C: Promotes hemoglobin synthesis, collagen synthesis, and sound connective tissue structure; an antioxidant that scavenges free radicals and possibly reduces the risk of cancer.
3) B12: To make healthy RBCs and prevent pernicious anemia; needs intrinsic factor to be absorbed

Question 20

1) What is hypervitaminosis and one likely cause?
2) Why is it more likely with fat-soluble vitamins?
3) What is the most common vitamin deficiency and what does it cause?

Answer 20

1) The excess of a (fat-soluble) vitamins; can be caused by taking megavitamins
2) Fat soluble vitamins are stored in the body, water soluble aren’t
3) Vitamin A deficiency: causes night blindness; dry skin, hair, and conjunctiva; cloudy cornea; and increased incidence of infections

Question 21

1) What is glucose catabolism and what is the function of this reaction?
2) Can you list the glucose catabolism reaction?

Answer 21

1) It’s carbohydrate metabolism; function of this reaction is to transfer energy from glucose to ATP
2) C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP + heat

Question 22

1) What is the major pathway of glucose catabolism?
2) What is the end product of this pathway?
3) Where can this end product be used?

Answer 22

1) Glycolysis
2) Pyruvate
3) In anaerobic fermentation or aerobic respiration

Question 23

1) Once you have the end product of glycolysis, in the absence of oxygen you go to what type of fermentation? 2) How many ATP are produced in the absence of oxygen?
3) Would this a way for the brain to get energy?
4) Would this be a way skeletal or cardiac muscle to get energy?

Answer 23

1) Anaerobic fermentation
2) Makes 2 ATP
3) The brain does not use anaerobic fermentation at all
4) Skeletal muscle is relatively tolerant of anaerobic fermentation, cardiac muscle less so

Question 24

What are the two major drawbacks to anaerobic fermentation?

Answer 24

1) Wasteful, because most of the energy of glucose is still in the lactate and has contributed no useful work
2) Lactate is toxic

Question 25

1) Once you have the end product of glycolysis, in the presence of oxygen you go to what type of fermentation? 2) How many ATP are produced in the presence of oxygen?

Answer 25

1) Aerobic respiration 2) 32-38 ATP per original glucose molecule

Question 26

If excess glucose is around, the body converts this to what two substances?

Answer 26

1) Glycogen 2) Fat

Question 27

1) Define glycogenesis? 2) What hormone stimulates glycogenesis?

Answer 27

1) The synthesis of glycogen from extra glucose 2) Insulin

Question 28

1) Define glycogenolysis? 2) What 2 hormones stimulates glycogenolysis? 3) What organ releases glucose into the blood?

Answer 28

1) The hydrolysis of glycogen between meals 2) Glucagon and epinephrine 3) The liver releases glucose into blood

Question 29

1) Define gluconeogenesis. 2) What organs are capable of doing gluconeogenesis?

Answer 29

1) The synthesis of glucose from noncarbohydrates, such as glycerol, amino acids, or keto acids 2) Mainly in liver, kidneys if needed

Question 30

Triglycerides are stored primarily in the body’s ________

Answer 30

adipocytes

Question 31

1) What is lipogenesis? 2) In lipogenesis, what is used to make the fatty acids and glycerol? 3) What is lipolysis? 4) What is catabolized in lipolysis? 5) What hormones stimulate lipolysis?

Answer 31

1) The synthesis of fat from other types of molecules 2) Amino acids and sugars 3) The breaking down of fat for fuel 4) Begins with the hydrolysis of a triglyceride to glycerol and fatty acids 5) Epinephrine, norepinephrine, glucocorticoids, thyroid hormone, and growth hormone

Question 32

Define ketosis and ketoacidosis.

Answer 32

Rapid or incomplete breakdown of fats (lipolysis) raises blood ketone levels (ketosis) and may lead to a pH imbalance (ketoacidosis)

Question 33

1) In protein metabolism, free amino acids can be converted to glucose or ___________________. 2) Can free amino acids be used directly as fuel?

Answer 33

1) fat 2) Yes, they can be used directly as fuel once NH2 is removed.

Question 34

1) In protein metabolism as fuel, NH2 is converted to ammonia (NH3). Ammonia is toxic so it has to be converted to what substance by what organ? 2) After the NH2 is removed, what’s left is called _______________. What can this be converted into?

Answer 34

1) Converted to urea by the liver 2) Keto acid; may be converted to pyruvate

Question 35

1) Protein metabolism: If keto acid is converted to pyruvate, what pathways can this enter? 2) Are these reactions reversible?

Answer 35

1) Aerobic respiration or anaerobic fermentation pathway 2) Yes, reversible in case there is a deficiency of amino acids

Question 36

1) Protein synthesis is stimulated by what hormones? 2) What is required components to perform protein synthesis?

Answer 36

1) Growth hormone and thyroid hormone 2) DNA, mRNA, tRNA, and ribosomes

Question 37

1) List some function of the liver? 2) What functions are performed by the hepatocytes? 3) What disorders of the liver are life-threatening?

Answer 37

1) Plays a wide variety of roles in carbohydrate, lipid, and protein metabolism; most of its functions are non-digestive 2) Hepatocytes perform all functions, except phagocytosis 3) Degenerative liver diseases such as hepatitis, cirrhosis, and liver cancer are especially life-threatening

Question 38

Define hypothermia, hyperthermia and thermoregulation. Include what hypothermia and hyperthermia can result in.

Answer 38

1) Hypothermia: Low body temperature; can slow metabolism and cause death 2) Hyperthermia: High body temperature; can disrupt coordination of metabolic pathways and cause death 3) Thermoregulation: the balance between heat production and loss

Question 39

What impact would hypothermia or hyperthermia have on enzyme function?

Answer 39

Enzymes that control our metabolism depend on an optimal, stable working temperature. To maintain this, heat loss must match heat generation; hyperthermia and hypothermia disrupt this

Question 40

1) When is “normal” body temperature at its’ lowest or highest? 2) The “core” temperature is the temperature of organs in what body cavities? 3) What is normal adult core temperature?

Answer 40

1) Low in morning and high in late afternoon; varies 1.8 degrees in a day 2) Cranial, thoracic, and abdominal cavities; rectal temperature is an estimate. 3) 99.0° to 99.7°F

Question 41

1) Where does most body heat come from? 2) At rest, what generates most of the heat? 3) During vigorous exercise, what generates most of the heat?

Answer 41

1) Catabolic reactions such as nutrient breakdown and ATP use 2) At rest: most heat is generated by the brain, heart, liver, and endocrine glands (skeletal 20-30%) 3) During vigorous exercise: the muscles produce 30 to 40 times as much heat as the rest of the body

Question 42

1) Is thermoregulation controlled by positive or negative feedback? 2) What organ is responsible for monitoring blood temperature? Where does it receive signals from?

Answer 42

1) Several negative feedback loops 2) The hypothalamus; receives signals from peripheral thermoreceptors in skin

Question 43

1) Is alcohol able to cross the blood-brain barrier? 2) What effect does alcohol have on the brain? 3) In the stomach and intestines? 4) What enzyme from what organ detoxifies alcohol?

Answer 43

1) Yes; alcohol crosses blood-brain barriers 2) Has intoxicating effects on the brain 3) Has negative physiological effects on the nervous system, circulatory system, digestive system (especially the liver) 4) Detoxified by liver enzyme alcohol dehydrogenase

Question 44

1) Which of the sexes, men or women, able to clear alcohol from the bloodstream the fastest? 2) Which of the sexes is more prone to cirrhosis of the liver?

Answer 44

1) Men 2) Women