Biology subject test (3)

MCAT Subject Tests
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_________________________________________________________________________ B I O L O G Y S U B J E C T T E S T 3

Biology Subject Test 3

5.
1.

Which enzyme changes disaccharides to
monosaccharides?
A
B.
C.
D.
E.

2.

A heart beat is initiated by the pacemaker, which is
also known as the atrioventricular (AV) node.
also known as the sinoatrial node.
located in the wall of the right ventricle.
functionally dependent upon nervous
stimulation.
E. located in the brain.

3.

6.

In the nervous system
A. myelination of nerves permits faster rates of
impulse conductance.
B. an excitatory neurotransmitter causes
hyperpolarization of the post-synaptic

membrane.
C. the autonomic nervous system mediates
voluntary functions.
D. during an action potential, first K+ rushes in.
E. during an action potential, first K+ rushes out of
the cell and then Na+ rushes in.

In the digestive system, all of the following are true
except
A. digestive enzymes from the pancreas are released
via a duct into the duodenum.
B. peristalsis is a wave of smooth muscle
contraction that proceeds along the digestive
tract.
C. in the small intestine, villi absorb nutrients into
both the lymphatic and circulatory systems.
D. the low pH of the stomach is essential for the
function of carbohydrate digestive enzymes.
E. the release of bile from the gall bladder is
triggered by the hormone cholecystokinin.

4.

A. Mature red blood cells are not nucleated.
B. Blood platelets are involved in the clotting
process.
C. The adult spleen is a site of red blood cell
development.
D. White blood cells are capable of phagocytosing
foreign matter.

E. New red blood cells are constantly developing in
the bone marrow.

Lactase
Kinase
Zymogen
Lipase
Phosphorylase

A.
B.
C.
D.

Which of the following statements about blood is
false?

7.

Which of the following is a normal pathway of blood
flow?
A.
B.
C.
D.
E.

Right ventricle to aorta
Pulmonary veins to left atrium
Inferior vena cava to left atrium

Pulmonary veins to left ventricle
Left ventricle to pulmonary artery

In the kidney
A. nephrons are located only in the cortex of the
organ.
B. ammonia is converted to urea.
C. both glucose and water are actively reabsorbed
from the glomerular filtrate.
D. antidiuretic hormone causes the reabsorption of
water from the collecting tubule.
E. filtration of the blood begins at the glomerulus
and ends at the loop of Henle.

8.

Which of the following associations of brain structure
and function is false?
A.
B.
C.
D.
E.

Hypothalamus : appetite
Cerebellum : motor coordination
Cerebral cortex : higher intellectual function
Reticular activating system : sensory processing
Medulla : basic emotional drives

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13. Which statement about the menstrual cycle is false?
9.

Which pairing of digestive enzyme and type of
substrate is incorrect?
A.
B.
C.
D.
E.

Ptyalin (salivary amylase) : proteins
Chymotrypsin : proteins
Carboxypeptidase : proteins
Pancreatic amylase : carbohydrates
Pancreatic lipase : fats

A. FSH causes the development of the primary
follicle.
B. LH causes the graafian follicle to undergo
ovulation.
C. The corpus luteum develops from the remains of
the post-ovulatory graafian follicle.
D. As a follicle develops, it produces estrogen.
E. FSH and LH are both posterior pituitary

secretions.

10. Which of the following statements about muscles is
false?
A. During isometric contraction the length of the
muscle is constant.
B. During isotonic contraction the length of the
muscle shortens.
C. In a resting muscle there is complete relaxation.
D. Tonus is the state of partial contraction that
occurs in the resting muscle.
E. Tetanus is a condition of sustained contraction
due to an overlap of twitch impulses.

11. Which statement about the respiratory system is NOT
true?
A. Ciliated nasal membranes warm, moisten, and
filter inspired air.
B. Contraction of the diaphragm enlarges the
thoracic cavity.
C. When the thoracic cavity enlarges, the pressure
of air within the lungs falls.
D. When the pressure of air within the lungs is less
than the atmospheric pressure, air will flow out
of the lungs.
E. The respiratory process consists of inspiratory
and expiratory acts following one another.

14. Which statement about pancreatic endocrine function
is FALSE?

A. Glucagon and insulin are both produced by islets
of Langerhans cells.
B. Glucagon and insulin are mutually antagonistic
in their behavior.
C. Glucagon and insulin both cause glucose to be
removed from the bloodstream and stored as
glycogen.
D. Glucagon causes an elevation in the level of
serum glucose.
E. Insulin causes a decrease in the level of serum
glucose.

15. Which of the following is an incorrect pairing of an
endocrine gland and hormone secretion?
A.
B.
C.
D.
E.

Posterior pituitary : LH
Adrenal cortex : aldosterone
Anterior pituitary : TSH
Adrenal medulla : epinephrine
Hypothalamus : FSH-releasing factor

16. What is the correct order that the body uses energy
sources?
12. All of the following statements about hormones are
true EXCEPT

A. they are transported by the circulatory system.
B. they bind to receptors on target cells.
C. they must be present in large quantities to have
an effect.
D. they are secreted by endocrine glands.
E. they can affect organs of the body that are far
removed from their site of synthesis.

2

A.
B.
C.
D.
E.

glucose ∅ fats ∅ proteins ∅ other carbohydrates
glucose ∅ other carbohydrates ∅ proteins ∅ fats
glucose ∅ other carbohydrates ∅ fats ∅ proteins
fats ∅ glucose ∅ other carbohydrates ∅ proteins
fats ∅ proteins ∅ glucose ∅ other carbohydrates

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17. Which statement about human gamete production is
false?
A. In the testes, sperm develop in the seminiferous

tubules.
B. In the ovaries, eggs develop in the ovarian
follicles.
C. FSH stimulates gamete production in both sexes.
D. Gametes arise via meiosis.
E. The result of meiosis in females is the
production of four egg cells.

18. Which of the following statements about evolution is
correct?
A. Lamarck's theory of use and disuse adequately
describes why giraffes have long necks.
B. Darwin's theory of natural selection relies solely
on genetic mutation.
C. Darwin's theory explains the evolution of man
from present day apes.
D. Darwin's theory of natural selection relies solely
on environmental conditions.
E. Natural selection is the process in which random
mutations are selected for survival by the
environment.

19. Where are amino acids absorbed?
A.
B.
C.
D.
E.

small intestine

large intestine
gall bladder
stomach
rectum

20. The hormone progesterone
A. stimulates follicle growth.
B. shuts off FSH production.
C. prepares the uterus for implantation of the
zygotes.
D. is solely responsible for the maintenance of
secondary sex characteristics.
E. is produced by the anterior pituitary.

21. To ensure survival of their species, animals that do
not care for their young must
A.
B.
C.
D.
E.

have the ability to live in water and on land.
lay eggs.
produce many offspring.
have protective coloring.
have internal fertilization.

22. Cerebellum damage will most likely
A.

B.
C.
D.
E.

impair memory.
impair coordination and equilibrium.
impair sense perception.
impair pituitary function.
impair breathing function.

23. Basal metabolism disorders are most likely caused
most directly by
A.
B.
C.
D.
E.

impairment of the pituitary.
impairment of the gonads.
impairment of the thyroid.
impairment of the thymus.
impairment of the parathyroid.

24. In the adult man, red blood cells are
A. non-nucleated and cannot repair themselves.
B. replaced in the liver.
C. outnumbered by white blood cells in the
circulation.

D. made in the spleen.
E. sites of rapid protein synthesis.

25. Which of the following is NOT reabsorbed from the
glomerular filtrate?
A.
B.
C.
D.
E.

glucose
Na+
ClK+
amino acids

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26. Estrogen
A. maintains female secondary sex characteristics.
B. promotes development of the follicle.
C. induces the ruptured follicle to develop into the
corpus luteum.
D. lowers blood glucose.
E. stimulates testosterone synthesis in males.

27. You've just been stopped for going 90mph in a 55mph

zone and this tickets means your license will be
suspended. As the police officer approaches your car,
which of the following is NOT occurring?
A.
B.
C.
D.
E.

Increased blood pressure.
Increased heart rate.
Dilated bronchioles.
Release of acetylcholine into the blood.
Increased pupil diameter.

28. The oxygen content is greatest in the fluid in which
of the following structures?
A.
B.
C
D.
E.

Pulmonary artery
Thoracic duct
Right atrium
Left ventricle
Inferior vena cava

29. What is the correct sequence of passages that air

travels through during exhalation?
A. alveoli ∅ bronchi ∅ bronchioles ∅ trachea
∅ pharynx
B. alveoli ∅ bronchi ∅ lungs ∅ trachea ∅ pharynx
C. alveoli ∅ trachea ∅ bronchi ∅ larynx ∅ pharynx
D. alveoli ∅ bronchi ∅ trachea ∅ larynx ∅ pharynx
E. alveoli ∅ bronchi ∅ trachea ∅ pharynx ∅ larynx

30. The rate of breathing is controlled by involuntary
centers in the
A.
B.
C.
D.
E.

4

cerebrum.
cerebellum.
medulla oblongata.
spinal cord.
hypothalamus.

31. Bones are connected to each other by connective
tissue known as
A.
B.
C.
D.

E.

sockets.
tendons.
ligaments.
synovia.
muscles.

32. Examples of environmental factors affecting the way
a gene is expressed include all of the following
except
A. Drosophila with a given set of genes have
crooked wings at low temperatures and straight
wings at high temperatures.
B. the change in hair color of the Himalayan hare
after cooling the naturally warm portions.
C. the production of heat shock proteins in a cell
after an increase in temperature.
D. a decrease in temperature causing shivering.
E. All of the above

33. Which of the following is not a disorder of the eye?
A.
B.
C.
D.
E.

Myopia
Hypermetropia

Glaucoma
Cataracts
All of the above are disorders of the eye

34. Which statement concerning the pituitary gland is
false?
A. The anterior pituitary secretes hormones involved
in the menstrual cycle.
B. The posterior pituitary directs the action of the
thyroid gland.
C. The hypothalamus secretes factors that cause the
release of anterior pituitary hormones.
D. Growth hormone is an anterior pituitary secretion.
E. The posterior pituitary can affect blood pressure.

35. Which of the following is not a lipid derivative?
A.
B.
C.
D.
E.

Waxes
Steroids
Carotenoids
Albumins
Lecithin

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36. Which of the following statements about viruses is
NOT true?
A.
B.
C.
D.

The genetic material may be DNA or RNA.
The virus may replicate in a bacterial host.
The virus may replicate in a eukaryotic host.
The virus may replicate autonomously in the
absence of a host.
E. The protein coat of the virus does not enter a
host bacterial cell.

37. In the kidney, blood filtered through the glomerulus
does not normally contain
A.
B.
C.
D.
E.

glucose.
amino acids.
blood cells.
sodium ions.

potassium ions.

40. Which statement about acetylcholine (ACh) is NOT
true?
A. ACh is released at the neuromuscular junction.
B. ACh binds to specific receptors on the postsynaptic membrane.
C. In a synaptic cleft there are enzymes that
degrade ACh
D. ACh diffuses through the pre-synaptic
membrane after its synthesis.
E. A synapse that is subjected to many action
potentials may be depleted of ACh granules.

STOP! END OF TEST.

38. According to Starling's hypothesis of capillary
physiology, which of the following is true?
A. The hydrostatic pressure is lower at the arteriolar
end.
B. The osmotic pressure tends to keep fluid out of
the vessel.
C. Filtration occurs where the hydrostatic pressure
is less than the osmotic pressure.
D. The ultrafiltrate is returned to the bloodstream
by the lymphatic system.
E. None of the above

39. Renin is a polypeptide produced
A.
B.

C.
D.
E.

in response to decreased blood pressure.
in response to increased blood volume.
in response to a concentrated urine.
which acts on the pituitary gland.
in the proximal convoluted tubules of the kidney.

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BIOLOGY SUBJECT TEST 3

ANSWER KEY

6

1. A

9. A

17. E

25. D

33. E

2. B

10. C

18. E

26. A

34. B

3. D

11. D

19. A

27. D

35. D

4. D

12. C

20. C

28. D

36. D

5. C

13. E

21. C

29. D

37. C

6. A

14. C

22. B

30. C

38. D

7. B

15. A

23. C

31. C

39. A

8. E

16. C

24. A

32. D

40. D

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EXPLANATIONS
1.

A
Lactase breaks lactose into glucose and galactose. Answer choice B is incorrect because kinase is an enzyme that
phosphorylates its substrate. Answer choice C is incorrect because zymogen is an enzyme that is secreted in an inactive
form. The zymogen is cleaved under certain physiological conditions to the active form of the enzyme. Important
examples of zymogens include pepsinogen, trypsinogen, and chymotrypsinogen, which are cleaved in the digestive tract to
yield the active enzymes pepsin, trypsin, and chymotrypsin. Answer choice D is incorrect because lipase breaks down
lipids into free fatty acids. Answer choice E is incorrect because phosphorylase removes a phosphate from its substrate.

2.

B

The heartbeat is initiated by the sinoatrial (SA) node located in the wall of the right atrium and travels through the
atria. It is regulated but not controlled by the accelerator nerve (sympathetic) and the vagus nerve (parasympathetic). It is
then picked up by the AV node which signals the bundle of His (AV bundle) which transports the contraction through the
ventricles via the Purkinje fibers. Answer choice A is incorrect because while the AV node does have contractile ability
and controls the contraction of the ventricles, it does not control the contraction of the entire heart and is not as regular as
the signal from the SA node. Answer choices C and D are not correct because the SA node is located in the wall of the
right atrium and is not functionally dependent upon nervous stimulation as this tissue initiates the heartbeat although it
can be modified by the nervous system.

3.

D
The low pH of the stomach is essential for the function of the enzymes that break down proteins into their amino
acids. Answer choice A is true: amylases, lipases, and bicarbonate are released through the pancreatic duct. Answer
choice B is true: peristalsis propels food and waste through the system. Answer choice C is true because glucose and
amino acids are picked up by the blood while fats are picked up by lacteals, which are special vessels that connect with the
lymphatic system. Answer choice E is true because cholecystokinin is a hormone released by the wall of the small
intestine due to the presence of acidic chyme from the stomach. It stimulates the gall bladder to release bile and the
pancreas to release digestive enzymes. Both secretions are released into the duodenum.

4.

D
ADH is released by the posterior pituitary gland and causes the collecting tubule to be more permeable to water.
Therefore, more water is absorbed and urine becomes more concentrated. Answer choice A is incorrect because in the
nephrons, the glomerulus, Bowman's capsule, and the proximal and distal convoluted tubule are in the cortex while the
loop of Henle and the collecting tubule are in the medulla. Answer choice B is incorrect because ammonia is transformed
into urea in the liver and excreted by the kidney. Answer choice C is incorrect because salts, glucose, and amino acids are
reabsorbed by active transport while water is reabsorbed by diffusion. Answer choice E is incorrect because filtration only
occurs at the glomerulus and Bowman's capsule.

5.

C
In the adult, all hematopoiesis occurs in the bone marrow. In the fetus, hematopoiesis occurs in the fetal liver. The
spleen acts as a reservoir for red blood cells and filters the blood. Answer choice A is true because mature red blood cells
are not nucleated in order to create more space for hemoglobin. Answer choice B is incorrect because blood platelets are
crucial for the clotting of blood, and answer choice D is incorrect because certain white blood cells such as macrophages
and neutrophils engulf foreign matter, and answer choice E is incorrect because new blood cells are continually being
produced in the bone marrow to replace the cells after their life span of 120 days has ended.

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6.

A
Myelin is a fatty compound that surrounds the axons and has been compared to insulation on a wire. It speeds
conduction along the nerve cell, and is produced by Schwann cells. Answer choice B is incorrect because depolarization
actually occurs after release of an excitatory neurotransmitter. Hyperpolarization actually makes it more difficult for an
action potential to occur. Answer choice C is incorrect because the autonomic nervous system is made up of the
sympathetic and parasympathetic nervous systems and regulates involuntary actions with opposing results. Answer
choices D and E are incorrect because sodium channels open first and Na+ rushes in, then K+ channels open and release
potassium out of the cell.

7.

B

Blood traveling from the left ventricle will flow into the aorta, then go to all areas of the body except the lungs. For
example, blood in the brachiocephalic artery will travel to the head and the shoulders, and blood in the renal artery will
travel to the kidney to be filtered. Blood will go from these arteries into arterioles, then capillaries, where food, waste, and
energy will be exchanged. Then the blood will go into venules and collect in veins, and will be transported to the superior
and inferior vena cavae. This makes up the systemic circulation. Then the blood will enter the right atrium and flow into
the right ventricle. After this it will be transported to the lungs via the pulmonary artery where capillary beds will
surround the alveoli so gas exchange can occur. Then the pulmonary veins will bring it back to the left atrium to start the
process over again. This is known as pulmonary circulation. Looking at the answer choices, only B follows this flow
chart.

8.

E
The medulla monitors blood carbon dioxide levels and pH, and adjusts breathing, temperature, and heart rate. It is
also the center for reflex activities such as coughing, sneezing, and swallowing. Answer choice A is true because the
hypothalamus is the center that controls thirst, hunger, sleep, blood pressure, and water balance. Answer choice B is true
because the cerebellum controls muscle coordination and tone, and maintains posture. Answer choice C is true because
the cerebral cortex is the center for vision, hearing, smell, voluntary movement, and memory. Answer choice D is true
because the reticular activating system receives and sorts sensory input.

9.

A
Salivary amylase digests starch into maltose. All the other enzymes are correctly paired with their substrates.

10.

C
Even in resting muscles there is a slight contraction known as tonus. Answer choice A is true because in isometric
contraction, there is constant length and an increase in muscle tension. Answer choice B is true because in isotonic

contraction, the muscle shortens while the tension remains constant. Answer choice D is true because tonus is the partial
sustained contraction in relaxed muscles. Answer choice E is true because in tetanus, there is no complete recovery before
the next sustained contraction. This will cause muscle contraction until fatigue because of lack of energy or a build up of
waste occurs.

11.

D
Answer choice D is false and therefore the correct answer because when the pressure of air within the lungs is less
than atmospheric, air actually rushes into the lungs. Answer choices B and C are correct because there is low pressure
inside the thoracic cavity due to the expansion of the thoracic volume when the diaphragm contracts. Answer choice A is
true because when this pressure drops, air rushes in and the ciliated membranes warm, moisten, and filter the inspired air.
Air then travels through the bronchi, into the bronchioles and finally into the alveoli where diffusion occurs to oxygenate
the blood and release CO2 carried back from the tissue.

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12.

C
Hormones are capable of being effective at picomolar concentrations. Answer choices A and D are true because they
are transported by the circulatory system after being secreted by the endocrine (ductless) glands. Answer choice E is true
because they may travel far from their site of synthesis to have an effect on their target organ. Answer choice B is true
because cells will respond to hormones only if they have the appropriate receptor on their cell surface in the case of peptide
hormones, or inside their cytoplasm in the case of steroid hormones.

13.

E
FSH and LH are secreted by the anterior pituitary, and affect the maturation of the follicle. FSH stimulates the
production of estrogen, and aids in the maturation of the primary follicle. LH causes the corpus luteum to secrete
progesterone, which causes the uterine lining to thicken to prepare for implantation.

14.

C
The pancreas is a dual organ with both endocrine and exocrine functions. Its exocrine function is to release digestive
enzymes and bicarbonate into the small intestine via the pancreatic duct. Its endocrine function is to release insulin,
produced by the b cells in the islets of Langerhans, and glucagon, produced by a cells, into the bloodstream. These
antagonistic molecules work together to regulate levels of blood glucose. Insulin causes a decrease of blood glucose by
stimulating the formation of glycogen. Glucagon causes an increase in blood glucose by catabolizing the breakdown of
glycogen into glucose.

15.

A
The posterior pituitary only secretes ADH and oxytocin. Answer choice B is correct because the adrenal cortex does
secrete aldosterone, which is a mineral cortisone that causes the increase of absorption of Na+. Answer choice C is correct
because the anterior pituitary does secrete TSH, which stimulates thyroid production of thyroxin, which raises the basal
metabolic rate. Answer choice D is correct because the adrenal medulla does secrete epinephrine, which increases heart
rate and blood pressure, and the flow of the blood to skeletal muscle. Answer choice E is correct because the
hypothalamus secretes FSH-releasing factor, which stimulates the anterior pituitary.

16.

C
When glucose supplies run low, the body utilizes other energy sources. These sources are used by the body in the
following preferential order: other carbohydrates, fats, and proteins. These substances are first converted to either glucose
or glucose intermediates, which can then be degraded in the glycolytic pathway and the citric acid cycle. Proteins are the
last resource for energy because there is no protein storage in the body. Utilization of protein results in muscle wasting
and connective tissue breakdown, which can be harmful in the long term.

17.

E
Oogenesis produces only one viable egg and two or three polar bodies. This is a result of unequal distribution of the
cytoplasm during meiosis. Answer choice A is true because interstitial cells are stimulated by LH to produce testosterone.
FSH and testosterone then cause the development of sperm in the seminiferous tubules. Answer choice B is true because
eggs develop in follicles in the ovaries under the control of FSH. Answer choice C is true because obviously FSH plays a
role in gamete production in both sexes. Answer choice D is true because gametes become haploid through reductional
division (meiosis) in which a diploid cell gives rise to four haploid sperm or one haploid egg and two or three polar bodies.

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18.

E
This statement is correct. Natural selection is the process by which mutations are "tried out" in the environment and
if they offer some degree of fitness, they will be passed on to the next generation. Answer choice A, Lamarck's theory, was
if something was used, such as a giraffe stretching its neck until it became longer, these acquired traits would be passed on
to the next generation. We know, however, that acquired characteristics do not affect the genes, and are therefore not
passed on to the next generation. Answer choice B is incorrect because Darwin's theory is much more than mutation. It is

based on overreproduction, which allows for genetic variation among the offspring. These offspring are then selected on
whether their genetic makeup is the most fit, and these most fit organisms will pass on their genes to the next generation.
Answer choice C is incorrect because Darwin believed that man and apes actually evolved from a common ancestor. And
answer choice D is incorrect because natural selection includes selection pressures but also needs a population with genetic
variation in order to select the most fit organisms.

19.

A
The small intestine is where chemical digestion is completed and absorption takes place. The small intestine is
highly adapted to absorption due to it's large surface area formed by finger-like projections called villi. Amino acids and
monosaccharides pass through the villi walls and enter into the capillary system within the villi.
Choice B, the large intestine, functions in the absorption of salts and water.
Choice C, the gall bladder, stores the bile prior to its release in the small intestine.
Choice D, the stomach, is a large muscular organ that stores, mixes and partially digests food.
Choice E, the rectum, provides for transient storage of feces prior to elimination through the anus.

20.

C
Progesterone readies the uterus for implantation by thickening and vascularizing the uterine lining. Answer choice
A is incorrect because FSH secreted by the anterior pituitary actually stimulates follicle growth. Answer choice B is
incorrect because the production of estrogen by the ovaries actually shuts off FSH secretion. Answer choice D is incorrect
because estrogen and testosterone are responsible for the secondary sex characteristics of females and males respectively.
Answer choice E is incorrect because FSH and LH are produced by the anterior pituitary.

21.

C
There are many types of fertilization/development/care in nature. At one end of the spectrum would be internal

fertilization, internal development, and lots of care. These organisms, such as elephants, produce few offspring but a large
percentage of the offspring produced reach adulthood. The other end of the spectrum would be external fertilization,
external development, and no care. These organisms, such as many species of fish, must produce large numbers of both
eggs and sperm as relatively few eggs and sperm will even interact to produce a zygote. Then, without any protection,
these zygotes are susceptible to predation. Therefore, millions of eggs and sperm must be released in order to perpetuate
the species. Answer choice A does not help these organisms at all, and while answer choice D might be useful, it is not
related to whether or not the young are cared for.

22.

B
The cerebellum is involved in fine motor coordination, balance, and equilibrium so damage to this section of the
brain will result in loss of these functions. A patient might become jerky and have erratic fine motor skills and lose his
balance easily. Answer choices A and C would result after trauma to the cerebrum, and answer choice D would result in
the impairment of a large number of body functions that depend on hormones secreted by the pituitary gland. Answer
choice E would result after damage to the medulla oblongata, which controls breathing rates.

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23.

C
The thyroid gland controls the basal metabolic rate through release of thyroxin. It is stimulated by TSH released by
the anterior pituitary gland. Answer choice A is incorrect because impairment of the pituitary would result in a myriad of
disorders as the anterior and posterior pituitary glands secrete a large number of hormones such as ACTH, LH, FSH,

ADH, and GH, which control a large number of bodily functions. Answer choice B is incorrect because impairment of the
gonads would result in a loss of FSH and LH from the anterior pituitary. Answer choice D is incorrect because the thymus
is involved in the development, maturation, and education of T cells. Answer choice E is incorrect because parathyroid
hormone stimulates calcium resorption from bone and increases plasma Ca2+ levels as a result.

24.

A
Red blood cells are produced in the bone marrow. They lose their nucleus to make room for more hemoglobin so
they cannot reproduce, repair themselves, or make proteins. Answer choice C is incorrect because RBCs actually highly
outnumber leukocytes, and answer choice D is incorrect because the spleen stores a reservoir of red blood cells and acts as
a biological and physical filter for the blood.

25.

D
K+ is considered a waste product and is secreted into the distal convoluted tubule.
Glucose and amino acids are reabsorbed in the proximal convoluted tubule. Na+ and Cl- are reabsorbed everywhere
but the descending limb and collecting duct. Water is reabsorbed everywhere but the ascending limb (where only salt is
pumped out).

26.

A
Estrogens are steroid hormones necessary for normal female maturation. Estrogen stimulates the development of the
female reproductive tract and contributes to the development of secondary sexual characteristics and sex drive. Estrogens
are also secreted by the follicle during the menstrual cycle and are responsible for the thickening of the endometrium.
Choice B is incorrect because it is FSH released from the anterior pituitary that promotes the development of the
follicle, which matures and begins secreting estrogen.
Choice C is describing the function of LH in the female menstrual cycle.

Choice D is describing insulin function. Insulin is a protein hormone secreted in response to a high blood glucose
concentration and stimulates the uptake of glucose by muscle and adipose cells.
Choice E is another function of LH.

27.

D
The situation described would stimulate the sympathetic nervous system. Acetylcholine is a neurotransmitter and is
not released into the bloodstream. Also, acetylcholine is the primary neurotransmitter in a parasympathetic nervous
response, not sympathetic.
Choices A, B, C and E are all responses stimulated by the sympathetic nervous system. The primary
neurotransmitter for this nervous system is norepinephrine.

28.

D
Blood in the left ventricle has just returned from the lungs where it was oxygenated via the pulmonary vein. This is
the only vein in the adult body that carries oxygenated blood. Answer choice A is incorrect because the pulmonary artery
is blood on its way to the lungs to be oxygenated. It is actually the most deoxygenated blood in the body. Answer choice B

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is incorrect because lymph vessels such as the thoracic duct are returning lymphatic fluid back to the venous circulation.
They have a very low partial pressure of O2. Answer choice C is incorrect because the right atrium has a low O2 content
as blood returning from the body is collected here before being transported to the lungs. Answer choice E is incorrect
because the inferior vena cava returns deoxygenated blood to the heart from the lower half of the body.

29.

D
The exhalation process begins in the alveoli then goes through the bronchioles to the bronchi, then it travels through
the trachea where it passes through the larynx and then the pharynx.

30.

C
The breathing center in the medulla oblongata monitors the increase in CO2 through its sensory cells. It also will
detect a decrease in pH in the blood, which is also indicative of an increase of CO2 levels in the blood. A decrease in O2 is
monitored peripherally by chemoreceptors in the carotid bodies in the carotid arteries, and aortic bodies in the aorta.
Answer choice A is incorrect because the cerebrum is involved in sensory interpretation, memory, and thought. Answer
choice B is incorrect because the cerebellum is involved in fine motor coordination, balance, and equilibrium. Answer
choice D is incorrect because the spinal cord relays sensory and motor information to and from the brain. Answer choice
E is incorrect because the hypothalamus regulates hunger, thirst, body temperature, sex drive, and emotion.

31.

C
Ligaments are fibrous connective tissue that link bone to bone, while answer choice B is incorrect because tendons
are fibrous connective tissue that connect bone to muscle. Answer choice A is incorrect because sockets are types of joints
such as the ball and socket joint of the hip. Answer choice D is incorrect because the synovia is the lining of synovial
joints and are meant to ease the friction between bones. Answer choice E is incorrect because muscles actually do connect
bones via their origin and insertion points, but they are not connective tissue. Rather they are contractile tissue.

32.

D
Genes supply the hereditary background, but the environment determines the way in which the gene is expressed.

Thus, the genetic and environmental factors interact to produce the phenotype of the individual. Answer choices A, B,
and C are all examples of the environment affecting what genes are transcribed. Answer choice D is an example of a
change in environment causing an effect to maintain homeostasis. Shivering generates heat because muscles are
contracting rapidly.

33.

E
In myopia (nearsightedness), the image forms in front of the retina. In hypermetropia (farsightedness), the image
forms behind the retina. Glaucoma is an increase of pressure in the aqueous humor due to the blocking of the outflow of
the aqueous humor. Cataracts occur when the lens becomes opaque and no light can enter the eye, resulting in blindness.

34.

B
The anterior pituitary secretes Thyroid Stimulating Hormone (TSH), which directs the action of the thyroid gland.
Choice A is incorrect because the anterior pituitary secretes Follicle Stimulating Hormone (FSH), which stimulates
follicle maturation and estrogen release, and Luteinizing Hormone (LH), which causes ovum release and progesterone
release.
The hypothalamus, choice C, secretes several hormones into the hypothalamic portal system that controls the release
of the anterior pituitary hormones. An example is GnRH, which controls the release of FSH and LH.

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Growth hormone, choice D, is secreted by the anterior pituitary. HG promotes bone and muscle growth, and is

involved in fat metabolism.
The posterior pituitary can affect blood pressure, choice E, through the action of AntiDiuretic Hormone (ADH,
vasopressin). ADH can indirectly increase blood pressure by increasing blood volume by increasing water reabsorption in
the nephron.

35.

D
Albumins are globular proteins that act as carriers, enzymes, and have a variety of other functions in the body.
Waxes are esters of fatty acids and monohydroxylic alcohols. They are found as protective coatings on skin, fur, leaves of
higher plants, and on the cuticle of the exoskeleton of many insects. Steroids such as cholesterol and estrogen have three
fused cyclohexane rings and one fused cyclopentane ring. Carotenoids are fatty acid-like carbon chains containing
conjugated double bonds and carrying six-membered carbon rings at each end. These compounds are pigments and they
produce red, yellow, orange, and brown colors in plants and animals. Lecithin is an example of a phospholipid.
Phospholipids contain glycerol, two fatty acids, a phosphate group, and nitrogen-containing alcohol.

36.

D
A virus is a simple non-living organism that takes on living characteristics when it enters cells that support its
replication. They are made up of genetic material, either DNA or RNA, and a protein coat, and must replicate within its
host cell. A bacteriophage will inject its DNA into the bacterium while leaving the protein coat on the cell surface. In
eukaryotes, however, the whole virus may enter the cell and not become unencapsulated until it enters the cytoplasm.

37.

C
The glomerulus is a capillary ball in the nephron where glucose, water, amino acids, ions, and urea enter while
plasma proteins and cells remain behind. Glucose and amino acids are filtered and completely reabsorbed, while urea is
filtered and excreted, and Na+ and other salts are filtered and partially reabsorbed. Therefore, blood filtered through the

glomerulus would not contain blood cells.

38.

D
The movement of fluids occurs between the capillaries and the surrounding tissues. Plasma proteins and fluids leave
at the arterial end of the capillary bed and reenter at the venule end. In between they exchange wastes, food, and fluids
with the cells. There are two forces that affect this movement. 1) The hydrostatic pressure, which is greater at the
arterial end (and much greater than the osmotic pressure), drives fluid out of the vessels into the interstitial spaces. 2)
The osmotic pressure, which is greater at the venule end (and much greater than the hydrostatic pressure), drives fluids
back into the vessels to be returned to the circulatory system. However, according to Starling's hypothesis, all of the fluid
cannot be returned to the vessel. Instead, some of this fluid travels through the interstitial spaces until it is picked up by
the lymphatic system where it is filtered through the lymph nodes and returns to the circulatory system via the thoracic
duct.

39.

A
Renin is part of the renin-angiotensin system, which aids in controlling blood pressure in the body. When blood
pressure falls (due to heavy bleeding for example) renin is released by the kidneys and converts angiotensinogen to
angiotensin I. Angiotensin converting enzyme (ACE), which is also present in the blood, converts angiotensin I to
angiotensin II. Angiotensin II causes vasoconstricion (angio = blood vessel; e.g. angioplasty: inserting a plastic balloon
into a blood vessel; tensin = tense; constrict) resulting in an increase in blood pressure. It also causes the release of
aldosterone from the adrenal cortex, which opens ion channels in the convoluted tubule of the kidney to increase water
resorption. Renin is formed by the juxtoglomerular apparatus near the distal convoluted tubule in the nephron. It acts
indirectly on the adrenal cortex but does not act on the pituitary gland.

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40.

D
Acetylcholine (ACh) is released at the neuromuscular junction when vesicles containing this neurotransmitter merge
with the membrane. ACh diffuses across the synapse and binds to specific receptors on the post-synaptic membrane. An
enzyme known as acetylcholinesterase degrades ACh very quickly after release in order to prevent constant stimulation of
the synapse.

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