diating from the body.
Metabolic rate falls in old age because muscle
mass declines and physical activity tends to be reduced.
tion can be inﬂuenced and impaired by alcohol, certain antibiotics that
interfere with food absorption, other drugs that may cause electrolyte
imbalances, and use of mineral oil.
Review Questions 1.
Case Study 1.
Blood pH: Low (normal: 7.35–7.45); Blood glucose: High
(normal: 70–120 mg/dl); Blood ketone bodies: High (normally negative);
Urine pH: Low (normal: 4.5–8.0)
Ketone bodies have an acetone smell
that can be detected in the urine and the breath. Mr. Boulard is produc-
ing abnormal amounts of ketone bodies, which are accumulating in his
blood. Tese substances are being excreted into the urine and diﬀusing
out of the lungs and into the exhaled air.
Ketogenesis, or the produc-
tion of ketone bodies, is a process that occurs primarily in hepatocytes
(liver cells) when carbohydrates are unavailable as an energy source. In
this case, the hepatocytes metabolize fats. Te fatty acids produced from
fat breakdown (lipolysis) are converted to acetyl CoA by beta oxidation.
In the absence of glucose, these acetyl CoA molecules cannot enter the
Krebs cycle, and hepatocytes convert them into ketone bodies.
Boulard’s elevated blood glucose and his acidotic state indicate diabetes
mellitus. In both type 1 and type 2 diabetes, the absence of insulin’s ac-
tions means that the cells are unable to eﬃciently take up and utilize
glucose from the blood. As a result, blood glucose levels are high, yet the
cells are forced to switch to an alternative energy source such as lipids,
which results in the production of ketone bodies in a diabetic patient.
Te stress of alcohol-induced dehydration can trigger ketoacidosis by
causing the release of stress hormones that make diabetes worse.
pH of Mr. Boulard’s blood and urine is abnormally low because ketone
bodies are acidic (keto acids). As the concentration of ketone bodies in
the blood rises, the blood pH falls (acidosis). Te kidneys correct the
blood pH by moving ketone bodies into the urine, making acidic urine.
Check Your Understanding 1.
Te lower part of his rib cage and the peri-
renal fat capsule protect his kidneys from blows.
Te layers of supportive
tissue around each kidney are the ﬁbrous capsule, the perirenal fat capsule,
and the renal fascia. Te parietal peritoneum overlies the anterior renal
Te renal pelvis, which has extensions called calyces, is continu-
ous with the ureter.
Filtrate is formed in the glomerular capsule and then
passes through the proximal convoluted tubule (PC±), the descending
and ascending limbs of the nephron loop, and the distal convoluted tubule
Te structural diﬀerences are (1) juxtamedullary nephrons have
long nephron loops (with long thin segments) and renal corpuscles that
are near the cortex-medulla junction, whereas cortical nephrons have short
nephron loops and renal corpuscles that lie more superﬁcially in the cortex;
(2) eﬀerent arterioles of juxtamedullary nephrons supply vasa recta, while
eﬀerent arterioles of cortical nephrons supply peritubular capillaries.
glomerular capillaries are fenestrated capillaries. (See Figure 19.3 on p. 697
to refresh your memory of capillary types.) Teir function is to ﬁlter large
amounts of plasma into the glomerular capsule.
Intrinsic controls serve to
maintain a nearly constant GFR in spite of changes in systemic blood pres-
sure. Extrinsic controls serve to maintain systemic blood pressure.
ﬁltration pressure is 5 mm Hg [50 mm Hg
(25 mm Hg
20 mm Hg)].
Hydrostatic pressure in the glomerular capillaries (HP
) is regulated by
intrinsic and extrinsic controls of GFR.
Te majority of reabsorption
occurs in the proximal convoluted tubule.
In primary active transport,
the energy for the process is provided directly by the cleavage of A±P. In
secondary active transport, the energy for the process is provided by the
concentration gradient. As Na
moves down its own concentration
gradient established by the active pumping of Na
occurring elsewhere in
the cell, it drives the movement of another substance (e.g., glucose) against
(legumes) and grains (wheat) are good sources of protein, but neither is
a complete one. However, together they provide all the essential amino
Vitamins serve as the basis for coenzymes, which work with en-
zymes to accomplish metabolic reactions.
factor to be absorbed by the intestine.
Iodine is essential for thyroxine
synthesis. Calcium in the form of bone salts is needed to make bones
hard. Iron is needed to make functional hemoglobin.
A redox reac-
tion is a combination of an oxidation and a reduction reaction. As one
substance is oxidized, another is reduced.
Some of the energy released
during catabolism is captured in the bonds of A±P, which provides the
energy needed to carry out the constructive activities of anabolism.
Te energy released during the oxidation of food fuels is used to
pump protons across the inner mitochondrial membrane.
strate-level phosphorylation, high-energy phosphate groups are trans-
ferred directly from phosphorylated intermediates to ADP to form A±P.
In oxidative phosphorylation, electron transport proteins forming part of
the mitochondrial cristae use energy released during oxidation of glucose
to create a steep gradient for protons across the crista membrane. Ten
as protons ﬂow back through the membrane, gradient energy is captured
to attach phosphate to ADP.
If oxygen is not available, glycolysis will
stop because the supply of NAD
is limited and glycolysis can continue
only if the reduced coenzymes (NADH
) formed during glycolysis
are relieved of their extra hydrogen.
Oxidation (via removal of H) is
common in the Krebs cycle; it is indicated by the reduction of a coen-
zyme (either NAD
or FAD). Decarboxylations are also common, and
are indicated by the removal of CO
from the cycle.
is the reaction in which glycogen is broken down to its glucose units.
Carbo loading forces the skeletal muscles to store more glycogen than
they ordinarily would.
Glycerol, a breakdown product of fat metabo-
lism, enters the glycolytic pathway.
Acetyl CoA is the central mole-
cule of fat metabolism.
Te products of beta oxidation are acetyl CoA
coenzyme A), NADH
, and FADH
uses keto acids drained oﬀ the Krebs cycle and amino groups (from other
nonessential amino acids) as substrates to make the nonessential amino
acids that the body needs.
Te ammonia removed from amino acids
is combined with carbon dioxide to form urea, which is then eliminated
by the kidneys.
Te three organs or tissues that regulate the directions
of interconversions in the nutrient pools are the liver, skeletal muscles,
and adipose tissues.
Anabolic reactions and energy storage typify
the absorptive state. Catabolic reactions (to increase blood sugar levels)
such as lipolysis and glycogenolysis, and glucose sparing occur in the
Te main antagonist of glucagon is insulin.
A rise in amino acid levels in blood increases both insulin and gluca-
High HDLs would be preferable because the cholesterol
these particles transport are destined for the liver and elimination from
A total cholesterol level of 200 mg/dl of blood or lower is
±rans fats are oils that have been hydrogenated (with
H atoms). Tey are unhealthy because they cause LDLs to increase and
HDLs to decrease, exactly the opposite of what is desirable.
short-term stimuli inﬂuencing feeding behavior are neural signals from
the digestive tract, nutrient signals related to energy stores, and GI tract
hormones (CCK, insulin, glucagon, and ghrelin).
Leptin is the most
important long-term regulator of feeding behavior.
Of the factors
listed, breathing and kidney function contribute to BMR.
has a larger relative body surface area and therefore has a higher BMR.
Te body’s core is the organs within the skull and the thoracic and
Cindy’s body temperature is rising as heat-
promoting mechanisms (shivering, chills) are activated. Something (an
infection?) has caused the hypothalamic thermostat to be set to a higher
level (fever) temporarily.
In conduction, heat is transferred directly
from one object to another (a hot surface to your palm). In convection,
air warmed by body heat is continually removed (warm air rises) and
replaced by cooler air (cool air falls), which in turn will absorb heat ra-