Biology subject test (4)

What is the probability of a tall child with blue eyes being born to a heterozygous tall, heterozygous brown-eyed mother and a homozygous tall, homozygous blue-eyed father, if tall heigh

MCAT Subject Tests

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Biology Subject Test 4

1 Which of the following produces bile?

A Small intestine

B Large intestine

C Gall bladder

D Liver

E Pancreas

2 In the adult man, red blood cells are produced in the

A spleen

B liver

C bone marrow

D heart

E veins

3 The sympathetic nervous system causes which of the

following?

A Constriction of the pupil

B Decreased heart rate

C Increased gastric secretion

D Reduction of adrenaline secretion

E Increased respiration

4 Epinephrine

A is synthesized by the adrenal cortex

B is a steroid hormone

C is released during parasympathetic stimulation

D is released by the adrenal medulla

E causes bronchial constriction when released into

the bloodstream

5 An action potential spike is due to

A increased permeability to K+

B increased permeability to Na+

C decreased permeability to Ca2+

D membrane hyperpolarization

E increased permeability to Cl–

6 Which statement about the heart is NOT true?

A The pacemaker is the SA node

B The SA node is capable of autonomous firing

C The vagus nerve can slow the heart rate

D Systolic pressure is lower than diastolic pressure

E Both ventricles contract simultaneously

7 In a reflex arc

A the sensory neuron synapses directly with the motor neuron

B sensory and motor neurons can synapse outside of the spinal cord

C sensory neurons synapse in the brain

D the motor response occurs without synaptic delay

E a minimum of three neurons must participate

8 Skeletal muscle has all of the following except

A multinucleated cells

B sarcoplasmic reticulum

C intercellular conductivity of action potentials

D individual innervations of each muscle fiber

E a regular array of molecular components

9 The liver performs all of the following functions except

A removal of bacteria from the bloodstream

B removal of bilirubin from the bloodstream

C synthesis of bile

D storage of bile

E synthesis of angiotensinogen

10 Pancreatic exocrine secretions contain all of the following EXCEPT

A proteases

B lipases

C amylases

D glucagon

E bicarbonate ions

11 Acetylcholine

A is secreted by the adrenal glands

B is the initial substrate in glycolysis

C is an intermediate in the citric acid cycle

D and norepinephrine act as transmitters across

synapses

E inhibits action potential transmission

12 A rectifier is an electrical device that allows current to

flow only in one direction In human physiology, an

analogous device is the

A axon

B dendrite

C synapse

D Schwann's sheath

E spinal nerve

13 What is the probability of a tall child with blue eyes

being born to a heterozygous tall, heterozygous

brown-eyed mother and a homozygous tall, homozygous

blue-eyed father, if tall height, and brown eye color are

dominant? (NOTE: the genes for eye color and height

are unlinked.)

A 1/4

B 1/2

C 3/4

D 1/8

E None of the above

14 If a gallstone blocked the duct leading from the

gallbladder, which of the following would be less easily

digested?

A Amino acids

B Proteins

C Fats

D Starch

E Glycogen

15 The cartilaginous structure that prevents food from

going down the trachea is the

A glottis

B epiglottis

C tongue

D larynx

E esophageal sphincter

16 In the speculation concerning the origins of life, one theory states that purines, pyrimidines, sugars, and phosphates combined to form

A nucleotides

B nucleosides

C carbohydrates

D fats

E proteins

17 Anaerobic respiration is less efficient than aerobic respiration because

A oxaloacetic acid serves as the final hydrogen acceptor

B it occurs in water

C it requires a greater expenditure of cell energy

D it requires a longer time for ATP production

E glucose molecules are incompletely oxidized

18 Muscle contraction depends on

A myosin and actin fibers simultaneously contracting

B myosin contraction only

C actin contraction only

D myosin and actin sliding over each other

E myosin expanding while actin contracts

19 In humans, most of digestion occurs in the

A mouth

B stomach

C liver

D small intestine

E pancreas

20 Which of the following is not a function of the human liver?

A Breakdown of amino acids to urea

B Regulation of blood sugar levels

C Detoxification of poisons

D Storage of glycogen

E Manufacture of red blood cells in the adult

21 If the pancreatic ducts of a human are tied off, which

of the following is mostly likely to occur in several

hours?

I Diabetic crisis

II Acromegaly

III Impaired digestion

A I only

B II only

C III only

D I and II

E II and III

22 Active transport is best defined as

A diffusion of soluble substances across a membrane

from a region of high concentration to low

concentration

B osmosis of water across a semi-permeable

membrane involving the hydrolysis of polypeptides

C the movement of materials across a semipermeable

membrane against an electrochemical gradient

D the movement of materials across a semipermeable

membrane with an electrochemical gradient

E the movement of substances across a membrane in

accordance with the Donnan equilibrium

23 Which of the following hormones raises the

concentration of blood calcium?

A Glucagon

B Calcitonin

C Parathyroid hormone

D Aldosterone

E Anti-diuretic hormone

24 Which of the following is not a necessary condition for

the Hardy-Weinberg equilibrium?

A Random mating

B Large gene pool

C Random emigration and immigration

D Forward mutation rate equals backward mutation

rate

E No inbreeding

25 Temperature regulation is a function of the

A medulla

B pons

C cerebrum

D pineal gland

E hypothalamus

26 Which of the following stimulates the conversion of glycogen to glucose?

A Insulin

B Parathyroid hormone

C Pepsin

D Glucagon

E Calcitonin

27 Which of the following events occurs first?

A Rupture of the Graafian follicle

B Secretion of estrogen

C Corpus luteum formation

D Progesterone release

E Decrease in FSH release by pituitary

28 Water absorption occurs primarily in the

A duodenum

B jejunum

C stomach

D large intestine

E mouth

29 Which of the following glands produces both exocrine and endocrine secretions?

A Parathyroid

B Adrenal

C Pituitary

D Parotid

E Pancreas

30 Continuous muscle contraction causes a buildup of lactic acid because

A it is a breakdown product of ADP

B it is a degredation product of phosphocreatine

C it is a metabolic end-product of anaerobic metabolism

D it is a breakdown product of fatty acid degradation

E actomyosin contraction releases cross-links of lactate

31 All viruses

A carry DNA

B carry RNA

C lack protein

D have chromosomes

E cannot reproduce outside of cells

32 Bile is a (an)

A hormone

B enzyme

C protein

D emulsifying agent

E protease

33 Which of the following directly supply the energy for

muscle contraction?

A Lactic acid

B Lactose

C ADP

D ATP and phosphocreatine

E cAMP and ATP

34 Hyperthyroidism is always associated with

A low blood pressure

B severely diminished mental activity

C high metabolic rate

D low body temperature

E decreased heart rate

35 Carbon monoxide, when inhaled, may be lethal

because

A of its irritation of the pleura

B of its preferential replacement of oxygen in

hemoglobin

C it forms insoluble complexes in the bloodstream

D it poisons the cytochrome system

E it directly inhibits the sodium pump

36 In which of the following would you find cristae?

A Endoplasmic reticulum

B Mitochondria

C Nucleus

D Nucleolus

E Ribosomes

37 Which of the following is NOT a metabolic waste

product?

A CO2

B lactate

C H2O

D pyruvate

E ammonia

38 Which stage of embryonic development consists of a hollow ball of cells surrounding a fluid filled center?

A Zygote

B Morula

C Blastula

D 2-Layer gastrula

E 3-Layer gastrula

39 Which of the following aspects of cellular respiration is correctly paired with the location in the cell where it occurs?

A Electron transport chain-inner mitochondrial membrane

B Glycolysis-inner mitochondrial membrane

C Krebs cycle-cytoplasm

D Fatty acid degradation-lysosomes

E ATP synthesis-outer mitochondrial membrane

40 Chemical X is found to denature all enzymes in the synaptic cleft What are the effects of chemical X on acetylcholine (ACh)?

A ACh is not released from the presynaptic membrane

B ACh does not bind to the postsynaptic membrane

C ACh is degraded before it acts on the postsynaptic membrane

D ACh is not inactivated in the synaptic cleft

E None of the above

STOP! END OF TEST

THE ANSWER KEY AND EXPLANATIONS BEGIN ON THE FOLLOWING PAGE

BIOLOGY SUBJECT TEST 4

ANSWER KEY

1 D

2 C

3 E

4 D

5 B

6 D

7 E

8 C

9 D

10 D

11 D

12 C

13 B

14 C

15 B

16 A

17 E

18 D

19 D

20 E

21 C

22 C

23 C

24 C

25 E

26 D

27 B

28 D

29 E

30 C

31 E

32 D

33 D

34 C

35 B

36 B

37 D

38 C

39 A

40 D

EXPLANATIONS

The liver produces bile Bile contains no enzymes; it emulsifies fats, breaking down large globules into small droplets

The small intestine, choice A, is where chemical digestion is completed and nutrients absorbed

The large intestine, choice B, functions in the absorption of salts and water

The gall bladder, choice C, stores the bile prior to its release in the small intestine

The pancreas, choice E, produces digestive enzymes (e.g amylase, trypsin, and lipase) and hormones (e.g insulin and glucagon)

Red blood cells are produced in the bone marrow In the fetus, they are produced in the liver Answer choice A is incorrect because the spleen stores a volume of blood and filters it but does not produce it Answer choice B is incorrect because the liver removes foreign material and detoxifies chemicals in the blood Answer choice D is incorrect because the heart provides the pressure that enables the blood to travel throughout the body Answer choice E is incorrect because the veins deliver blood to the heart

The sympathetic nervous system is known as the "fight or flight" response Stimulation of this branch of the

autonomic nervous system is characterized by an increase in heart rate, dilation of the pupils, an increase in respiration and bronchial dilation, and more blood to the skeletal muscles and away from the digestive organs Also, an increase in the amount of adrenaline secretion occurs Answer choices A–D are all characteristics of the antagonistic branch of the autonomic nervous system, the parasympathetic nervous system, known as the "rest and digest" response

Epinephrine, also known as adrenaline, is released by the adrenal medulla Answer choice C is incorrect because this release is stimulated by the sympathetic nervous system Answer choice B is incorrect because epinephrine is a peptide hormone; steroid hormones are produced by the adrenal cortex Answer choice E is incorrect because epinephrine causes bronchial dilation

An action potential spike refers to the depolarization of the axon First, the axon becomes more permeable to Na+

ions from the outside through the opening of sodium channels In rushes sodium, and then the potassium channels open and K+ rushes out of the axon Afterwards, the cell is returned to normal through the action of the Na+/K+ pump Answer choices C and E are incorrect because Ca2+ and Cl– ions are not associated with depolarization and answer choice D is incorrect because hyperpolarization actually makes an axon less likely to trigger an action potential

The heartbeat is initiated by the sino-atrial 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 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 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 The delay between the contraction of the atria and the ventricles allows for the filling of the ventricles with the blood from the atria The systolic pressure is actually higher than the diastolic pressure as the systolic pressure is the pressure of the ventricular contraction while the diastolic pressure is the pressure between contractions

A reflex arc is a stimulus coupled to a rapid motor response, and is meant for quickness or protection Examples of this are blinking or recoiling away from a hot stove An example of a reflex arc would begin with you touching a hot pot

on a stove, which would stimulate a sensory nerve The sensory nerve directs a signal towards the CNS, and synapses with an interneuron in the spinal cord The interneuron (which is entirely within the spinal cord) synapses with a motor neuron, which delivers the response signal to your arm and hand, causing you to involuntarily drop the pot and move your arm away The process requires no input from the brain Answer choice C is incorrect because although some sensory neurons due synapse in the brain, those that are involved in simple reflex arc do not Answer choice D is incorrect because there is a very brief delay that occurs at the two synaptic junctions (it takes time for the neurotransmitters to diffuse)

Skeletal muscle has multinucleated fibers with a regular array of actin and myosin filaments These filaments slide along each other and shorten during contraction This process requires ATP Each muscle cell/fiber is innervated by a branch of the nerve innervating this muscle The axon releases an action potential to each muscle fiber This action potential cannot pass from one muscle fiber to another When this action potential reaches the muscle fiber, it causes the release of Ca2+ from the sarcoplasmic reticulum to initiate the sliding of the actin and myosin filaments

The liver is a biochemical factory that stores sugar as glycogen in response to insulin levels; breaks down glycogen to glucose due to signals from glucagon and epinephrine; converts excess amino acids to glucose, fats, and ammonia; converts ammonia to urea for excretion; removes bacteria and bilirubin (which is utilized in the formation of bile salts) from the bloodstream; synthesizes angiotensinogen; and produces bile, which emulsifies fats Therefore, only answer choice D is not listed as a function of the liver but is rather a function of the gall bladder The liver produces the bile while the gall bladder stores it until it is needed

As an exocrine gland, the pancreas secretes proteases, lipases, and amylases, which aid in the digestion of food, and bicarbonate ions which buffer the pH of the chyme coming from the stomach Glucagon is an endocrine secretion of the pancreas in response to a low blood glucose level It causes an increase in the levels of glucose through the degradation of glycogen, and decreases the uptake by muscles

Acetylcholine is a neurotransmitter found in neuromuscular junctions and synapses Norepinephrine, dopamine, and serotonin are also neurotransmitters found in these locations They are chemical messengers released as action potential reaches the end of the axons After crossing the synaptic cleft, they cause the depolarization of the adjacent cell

membrane Answer choices A, B, and C are incorrect because acetylcholine isn't secreted by the adrenal glands and is not

involved in glycolysis or the citric acid cycle Answer choice E is incorrect because it does not inhibit an action potential, rather it causes an action potential

The synapse is a small space between an axon and dendrite of two neurons After stimulation, the axon will release a neurotransmitter across this cleft, which will diffuse and bind receptors on the dendrite of the next neuron The

neurotransmitter can only be released by the axon and can only be received by the dendrite and is therefore similar to a rectifier Answer choice A is incorrect because the axon is only the section of the neuron away from the cell body while answer choice B is incorrect because the dendrite is the section of the neuron going toward the cell body Answer choice

D is incorrect because Schwann cells are insulating cells of the neurons Answer choice E is incorrect because a spinal nerve is a bundle of nerves where they enter and exit the spinal cord

Let’s first define the alleles in this problem Let T equal tall height and t equal short height Now let’s define B as brown eye color, and b as blue eye color The father is described as homozygous tall and homozygous blue-eyed, so we know his genotype is TTbb The mother is described as heterozygous tall and heterozygous brown-eyed, so her genotype is TtBb This question asks you to determine the probability that these parents could produce a tall child with blue eyes (T_bb) Remember, the genes for height and eye color are unlinked Now, the father can only contribute the T and b alleles, so all of his gametes will have both the T and b alleles On the other hand, the mother can contribute either T or t and either B or b, so her gametes are the following, all in equal amounts: TB, tB, Tb, or tb Thus, the possible genotypes

of the offspring are: TTBb, TTbb, TtBb, Ttbb Half the offspring are tall and brown eyed, and the other half are tall and blue-eyed Therefore, the probability of a tall child with blue eyes is 1/2 (one out of two), or choice B A shorter method involves calculating phenotype ratios for height and eye-color seperately and then combining them The mating of TT x

Tt produces 100% tall The mating of Bb x Bb produces one half blue and one half brown Multiplying 1 tall times one half blue gives us one half tall blue, or choice B

Bile is formed in the liver and released by the gall bladder, and emulsifies fats to increase the surface area of the fat molecules so that lipases can break them down Therefore, without bile, fats would be more difficult to digest

The cartilaginous structure that prevents food from going down the trachea is known as the epiglottis This structure closes off the respiratory tract and covers the glottis, which is the opening at the top of the trachea Answer choice C is incorrect because the tongue is a muscle, not cartilage, and does not close off the trachea Answer choice D is incorrect because the larynx is also known as the voice box, and is located below the glottis Answer choice E is incorrect because the esophageal sphincter is also known as the cardiac sphincter, and separates the esophagus from the stomach

Nucleotides are made up of a nitrogenous base, guanine, uracil, adenine, cytosine, or thymine; a sugar, either ribose

or deoxyribose; and a phosphate group Adenine and guanine are purines while thymine, cytosine, and uracil are

pyrimidines Answer choice B is incorrect because a nucleoside does not contain the phosphate group, just the nitrogenous base and the sugar Answer choice C is incorrect because carbohydrates are only sugars, while answer choice D is

incorrect because fats are glycerols and three fatty acids Answer choice E is incorrect because proteins are only linked amino acids and do not contain anything found in a nucleotide