Page 1009 - Fundamentals of anatomy physiology

996 Unit 5 Environmental Exchange
25 tissues. The liver is the focal point for metabolic regulation
and control. Adipose tissue stores lipids, primarily in the form
of triglycerides. Skeletal muscle contains substantial glycogen
reserves, and the contractile proteins can be degraded and the
amino acids used as an energy source. Neural tissue does not
contain energy reserves; glucose must be supplied to it for en-
ergy. Other peripheral tissues are able to metabolize glucose,
fatty acids, or other substrates under the direction of the endo-
crine system.
24. For about four hours after a meal, nutrients enter the blood as
intestinal absorption proceeds. (Spotlight Figure 25–11)
25. The liver closely regulates the circulating levels of glucose and
amino acids.
26. The absorptive state exists when nutrients are being absorbed
by the digestive tract. Adipocytes remove fatty acids and glyc-
erol from the bloodstream and synthesize new triglycerides to
be stored for later use. (Spotlight Figure 25–11)
27. During the absorptive state, glucose molecules are catabolized
and amino acids are used to build proteins. Skeletal muscles
may also catabolize circulating fatty acids, and the energy
o­ btained is used to increase glycogen reserves.
28. The postabsorptive state extends from the end of the absorp-
tive state to the next meal. (Spotlight Figure 25–11)
29. When blood glucose levels fall, the liver begins breaking down
glycogen reserves and releasing glucose into the bloodstream.
As the time between meals increases, liver cells synthesize
g­ lucose molecules from smaller carbon fragments and from
glycerol molecules. Fatty acids undergo beta-oxidation; the
fragments enter the citric acid cycle or combine to form
ketone bodies. (Spotlight Figure 25–11)
30. Some amino acids can be converted to pyruvate and used for
gluconeogenesis; others, including most of the essential amino
acids, are converted to acetyl-CoA and are either catabolized or
converted to ketone bodies.
31. Neural tissue continues to be supplied with glucose as an en-
ergy source until blood glucose levels become very low.
25-6 Adequate nutrition is necessary to prevent deficiency
disorders and ensure physiological functioning p. 983
32. Nutrition is the absorption of nutrients from food. A bal-
anced diet contains all the ingredients needed to maintain
homeostasis; a balanced diet prevents malnutrition.
33. The five basic food groups are grains, vegetables, fruits, dairy,
and protein. These are arranged on a plate to reflect the recom-
mended daily food consumption balanced with daily physical
activity. (Figure 25–12; Table 25–1)
34. Amino acids, purines, pyrimidines, creatine, and porphyrins
are N compounds, which contain nitrogen atoms. An ade-
quate dietary supply of nitrogen is essential, because the body
does not maintain large nitrogen reserves. Nitrogen balance
Review Questions
LEVEL 1 Reviewing Facts and Terms
1. The complete catabolism of one glucose molecule typically yields
a net energy gain of (a) 32 ATP, (b) 36 ATP, (c) 36 ATP and 2 GTP,
(d) 34 ATP.
2. The breakdown of glucose to pyruvate is an ___________ process.
(a) anaerobic, (b) aerobic, (c) anabolic, (d) oxidative, (e) both a and d.
3. The sequence of cytochromes in the electron transfer chain is
(a) b, c, a, c, a3, (b) a, b, c, a3, (c) a3, a, c, b, (d) c, b, a, a3.
is a state in which the amount of nitrogen absorbed equals
that lost in urine and feces.
35. Minerals act as cofactors in a variety of enzymatic reactions.
They also contribute to the osmotic concentration of body
fluids and play a role in membrane potentials, action poten-
tials, the release of neurotransmitters, muscle contraction,
skeletal construction and maintenance, gas transport, buffer
systems, fluid absorption, and waste removal. (Table 25–2)
36. Vitamins are needed in very small amounts. Vitamins A, D, E,
and K are fat-soluble vitamins; taken in excess, they can lead
to hypervitaminosis. Water-soluble vitamins are not stored
in the body; a lack of adequate dietary supplies may lead to
hypovitaminosis (vitamin deficiency disease). (Tables 25–3, 25–4)
37. A balanced diet can improve one’s general health.
25-7 Metabolic rate is the average caloric expenditure, and
thermoregulation involves balancing heat-producing
and heat-losing mechanisms p. 988
38. The energy content of food is usually expressed in kilocalo-
ries (kcal) or as Calories per gram (Cal/g).
39. The catabolism of lipids releases 9.46 Cal/g, about twice the
amount released by equivalent weights of carbohydrates or
proteins.
40. The sum of all the anabolic and catabolic processes under way
is an individual’s metabolic rate. The basal metabolic rate
(BMR) is the rate of energy utilization by a person at rest.
(Figure 25–13)
41. The homeostatic regulation of body temperature is thermo-
regulation. Heat exchange with the environment involves
four processes: radiation, convection, evaporation, and
conduction. (Figure 25–14)
42. The preoptic area of the hypothalamus acts as the body’s thermo-
stat, affecting the heat-loss center and the heat-gain center.
43. Mechanisms for increasing heat loss include both physi-
ological mechanisms (peripheral vasodilation, increased
perspiration, and increased respiration) and behavioral
modifications.
44. Responses that conserve heat include a decreased blood
flow to the dermis and countercurrent exchange.
(Figure 25–15)
45. Heat is generated by shivering thermogenesis and
nonshivering thermogenesis.
46. Thermoregulatory responses differ among individuals. One
important source of variation is acclimatization (a physi-
ological adjustment to an environment over time).
47. Pyrexia is an elevated body temperature. Fever, a body tem-
perature above 37.2°C (99°F), can result from problems with
the thermoregulatory mechanism, circulation, or sweat gland
activity, or from the resetting of the hypothalamic “thermo-
stat” by circulating pyrogens.
See the blue Answers tab at the back of the book.
4. Beta oxidation is the (a) attachment of an amino group to a keto acid,
(b) breakdown of fatty acids into 2C fragments, (c) removal of an
amino group that produces ammonium, (d) conversion of ammo-
nium to urea.
5. The four functions that are supported by anabolism in cellular meta-
bolism are structural maintenance, cellular growth, ________________,
and nutrient storage.
6. State the functional roles of minerals within the body.