Biology subject test (5)

MCAT Subject Tests Dear Future Doctor, The following Subject Test and explanations contains questions not in test format and should be used to practice and to assess your mastery of the foundation content necessary for success on the MCAT Simply memorizing facts is not sufficient to achieve high scores; however, an incomplete understanding of basic science knowledge will limit your ability to think critically Think of building your content knowledge as learning the vocabulary and practicing MCAT-like questions as actually speaking All rights are reserved pursuant to the copyright laws and the contract clause in your enrollment agreement and as printed below Misdemeanor and felony infractions can severely limit your ability to be accepted to a medical program and a conviction can result in the removal of a medical license We offer this material for your practice in your own home as a courtesy and privilege Practice today so that you can perform on test day; this material was designed to give you every advantage on the MCAT and we wish you the best of luck in your preparation Sincerely, Albert Chen Executive Director, Pre-Health Research and Development Kaplan Test Prep © 2003 Kaplan, Inc All rights reserved No part of this book may be reproduced in any form, by Photostat, microfilm, xerography or any other means, or incorporated into any information retrieval system, electronic or mechanical without the written permission of Kaplan, Inc This book may not be duplicated, distributed or resold, pursuant to the terms of your Kaplan Enrollment Agreement  _ B I O L O G Y S U B J E C T T E S T Biology Subject Test What is the principal function of NaHCO3? A B C D Dissolves CO2 better Inactivates bile Acts as a buffer Combines with oxygen when hemoglobin is saturated E Combines with CO2 in alveoli A B C D E Lacteals absorb A B C D E A B C D E A It occurs in the cytoplasm B Glycolysis is anaerobic C molecule of glucose breaks down into one molecule of pyruvate D molecule of glucose results in the formation of net ATP and reduced molecules of NAD+ E Glucose is partially oxidized Which of the following is NOT true regarding DNA? Which of the following does not occur immediately after birth? The infant begins to produce adult hemoglobin Resistance in the pulmonary arteries decreases Pressure in the left atrium increases Pressure in both the inferior vena cava and the right atrium increases E The ductus arteriosus constricts 0% 3.125% 6.25% 12.5% 25% All of the following statements about the glycolytic pathway are true EXCEPT chloroplast microbody phagosome vacuole lysosome A B C D carbohydrates proteins fatty acids salts Two of the above If a strand of DNA underwent four rounds of replication, what percentage of the total DNA present would be comprised of the original DNA molecule? You isolate a membrane bound vesicle containing hydrolytic enzymes It is most likely a In a population in Hardy-Weinberg equilibrium, the frequency of the dominant allele D is three times that of the recessive allele d What is the frequency of heterozygotes in the population? A B C D E 6.25% 25% 37.5% 56.25% 75% Shortly after gastrulation, a teratogen affects the development of the endoderm You will most likely see a deformity in the A B C D E lens of the eye gonads nervous system bladder lining connective tissue 10 Which component of blood is involved in clot formation? A Erythrocytes The basic unit is a nucleotide B Macrophages Adenine and guanine are pyrimidines C T cells The strands are anti-parallel D B cells Guanine always binds with cytosine with three E Platelets hydrogen bonds E The sugar molecule is deoxyribose KAPLAN A B C D B I O L O G Y S U B J E C T T E S T 11 Which of the following is not secreted by the thyroid? A B C D E Thyroxine Triiodothyronine TSH All of the above None of the above 12 Hypothyroidism is always associated with A B C D E high blood pressure irritability low metabolic rate high body temperature decreased heart rate 13 Which of the following cellular substituents is made within the nucleus? A B C D E Lysosome Golgi apparatus Ribosome Smooth endoplasmic reticulum Cell membrane 14 A capillary has A a higher hydrostatic pressure at the arteriole end and a lower hydrostatic pressure at the venule end B a higher osmotic pressure in its blood plasma than the osmotic pressure of the interstitial fluid bathing the tissues C a hydrostatic pressure that results from the beating of the heart D Choices A and C only E Choices A, B and C 15 Which of the following elements is not found in nucleic acids? A B C D E Sulfur Carbon Oxygen Nitrogen Phosphorus 16 A colorblind male XcY is crossed with a normal female who is a carrier of fragile X and colorblindness (XfXc) What is the probability that a male child will be phenotypically normal? A B C D E 0% 25% 50% 75% 100% 17 Which of the following is NOT true regarding the cytoskeleton? A B C D E It is composed of microtubules and microfilaments It gives the cell mechanical support It maintains the cell's shape It is not required for mitosis It is functional in the cell's motility 18 One molecule of glucose is catabolized via cellular respiration How many molecules of ATP are produced by oxidative phosphorylation? A B C D E 32 36 40 19 Drosophila melanogaster can have several eye colors Red eyes are dominant over white eyes and sepia eyes If a red eyed fly that resulted from a mating of red eyed and sepia eyed parents is crossed with a sepia eyed fly, what percentage of the offspring will have sepia eyes? A B C D E 0% 25% 50% 75% 100% 20 The retina of the eye is a derivative of the A B C D E endoderm ectoderm mesoderm ectoderm and mesoderm mesoderm and endoderm KAPLAN _ B I O L O G Y S U B J E C T T E S T 21 Vitamin K absorption occurs mainly in the A B C D E duodenum jejunum stomach large intestine mouth 22 All of the following are characteristics of osmosis EXCEPT A Passive transport B Occurs with water C Solvent will spontaneously move from a hypertonic environment to a hypotonic environment D Solvent spontaneously moves from an area of high solvent concentration to low solvent concentration E Is a special form of diffusion 23 What region of the brain controls the breathing rate? A B C D E Medulla oblongata Hypothalamus Cerebrum Cerebellum Pituitary gland 26 All of the following occur in the mouth except A B C D E mechanical digestion moistening of food chemical digestion of proteins bolus formation chemical digestion of starch 27 Which of the following is TRUE about the role of LH in the menstrual cycle? A LH inhibits the secretion of GnRH B LH is secreted by the ovary C LH induces the ruptured follicle to become the corpus luteum and secrete progesterone and estrogen D LH stimulates the development and maintenance of the endometrium in preparation for implantation of the embryo E LH stimulates milk production after birth 28 Cardiac muscle A B C D E Is innervated by the somatic motor nervous system Is not striated Is multi-nucleated Has voluntary contraction Does not require Ca2+ 24 Which type of muscle is always multinucleated? A B C D E Cardiac muscle Skeletal muscle Smooth muscle A and B B and C 25 Which of the following hormones is released from the posterior pituitary? A B C D E Oxytocin FSH Glucagon Estrogen Calcitonin 29 Which of the following statements about the glycolytic pathway is true? A Oxygen serves as a major reactant in glycolysis B During glycolysis, glucose is partially reduced C For each molecule of glucose that undergoes glycolysis, two net molecules of ATP and two molecules of reduced NAD are produced D For each molecule of glucose that undergoes glycolysis, one molecule of pyruvic acid is formed E Pyruvic acid, the final product of the Krebs cycle, serves as the immediate fuel for the next series of cellular reactions 30 Which region of the kidney has the lowest solute concentration? A B C D E Nephron Cortex Medulla Pelvis Epithelia KAPLAN B I O L O G Y S U B J E C T T E S T 31 Which of the following hormones raises the concentration of blood calcium? A B C D E Glucagon Insulin Parathyroid hormone Aldosterone Anti-diuretic hormone 32 If a person lacks gamma globulin, he would have A B C D E severe allergies low resistance to infection diabetes hemophilia None of the above 33 Resting membrane potential depends on A The differential distribution of ions across the axon membrane B Active transport C Selective permeability D The Na+/K+ pump E All of the above 36 Which of the following is NOT made of cartilage? A B C D E Nose Middle ear Outer ear Skeletal Joint Larynx 37 Which of the following hormones directly affects blood sugar level? A B C D E Oxytocin Calcitonin Estrogen Glucagon Thyrotropin 38 At the arterial end of a capillary bed, the osmotic pressure A B C D E Is greater than the hydrostatic pressure Results in a net outflow of fluid Is less than the hydrostatic pressure Two of the above None of the above 39 Which of the following is NOT true about aldosterone? 34 Which of the following is generally a passive process A B C D E Inhalation Exhalation Gas exchange A and B B and C A B C D E Stimulates reabsorption of Na+ Stimulates secretion of K+ Results in the production of concentrated urine Produced by the adrenal cortex Known as vasopressin 40 The function of the lymph nodes is to 35 Which of the following is NOT true regarding the circulatory system? A B C D Mammals have a four chambered heart Veins have a strong pulse Arteries typically carry oxygenated blood The lymphatic system intersects with the circulatory system at the thoracic duct E The pumping chambers of the heart are called ventricles A B C D E Filter lymph Break down hemoglobin Increase glucose concentrations in blood Facilitate the absorption of amino acids Carry oxygen STOP! END OF TEST KAPLAN _ B I O L O G Y S U B J E C T T E S T THE ANSWER KEY AND EXPLANATIONS BEGIN ON THE FOLLOWING PAGE KAPLAN B I O L O G Y S U B J E C T T E S T BIOLOGY SUBJECT TEST ANSWER KEY C D 17 D 25 A 33 E C 10 E 18 C 26 C 34 E C 11 C 19 C 27 C 35 B C 12 C 20 B 28 D 36 B B 13 C 21 D 29 C 37 D E 14 E 22 C 30 B 38 D D 15 A 23 A 31 C 39 E C 16 A 24 B 32 B 40 A KAPLAN _ B I O L O G Y S U B J E C T T E S T Explanations C The principal function of sodium bicarbonate in the blood is to serve as a buffer to maintain a slightly basic (7.2) pH of the blood NaHCO3 is the conjugate base to H2CO3, which results from the combination of carbon dioxide and water: → + – CO2 + H2O → ← H2CO3 ← H + HCO3 C The small intestine are lined with finger-like projections called villi which serve to increase the absorptive surface area Within the core of the villi are capillaries and lacteals, which are lymphatic vessels Amino acids and glucose pass through the villi walls into the capillary Large fatty acids and glycerol pass into the lacteals and are then reconverted into fats Lymph and the absorbed fats will later empty into the central circulatory system C With each round of replication the original DNA material gets halved After rounds of replication the amount of 1 original DNA will = (2)4 = 16 = 6.25% The original strand of DNA is comprised of two sister strands After four rounds of replication, you would have 16 strands of DNA comprised of 32 sister strands The two original sister strands are 6.25% of the 32 sister strands that you have at the end of the replication C The statement in choice C is false: One molecule of glucose (6 carbon sugar) breaks down into two molecules of pyruvate (pyruvate is a carbon molecule) Hence this is the choice we are looking for Choice A is a true statement and therefore NOT the correct response: Glycolysis occurs in the cytoplasm Choice B is also true Glycolysis is anaerobic and occurs in both eukaryotes and prokaryotes In anaerobic conditions or in anaerobic bacteria, it is the first step in fermentation In eukaryotes, pyruvate is reduced to lactic acid and in prokaryotes, it is reduced to ethanol Choice D is an accurate statement In glycolysis, one molecule of glucose is broken down and ATP are formed However, due to the initial investment of ATP, the net production of ATP is Also, two molecules of NAD+ are reduced to NADH These molecules will later enter the electron transport chain to produce ATP B Adenine and guanine are purines while cytosine, uracil and thymine are pyrimidines Choice A is an accurate statement The basic unit of DNA is a nucleotide which is made up of a phosphate group, a deoxyribose sugar, and a nucleic acid Choice C is also a true statement: The strands are antiparallel, that is, one strand has a 5’ ∅ 3’ polarity and its complementary strand has a 3’ ∅ 5’ polarity Choice D is correct Guanine always bonds with cytosine with three hydrogen bonds Adenine will bond with either thymine or uracil with two hydrogen bonds Choice E is correct The sugar molecule in DNA is deoxyribose while in RNA it is ribose KAPLAN B I O L O G Y S U B J E C T T E S T E The lysosome is like the stomach of the cell and is characterized as a membrane bound organelle that stores hydrolytic enzymes Choice A is incorrect because chloroplasts are found only in algae an plant cells They contain chlorophyll and are the site of photosynthesis Chloroplasts contain their own DNA and ribosomes and may have evolved by symbiosis Choice B is incorrect because microbodies are membrane bound organelles specialized as containers for metabolic reactions Choice C is incorrect because phagosomes are vesicles that are involved in the transport and storage of materials that are ingested by the cell through phagocytosis Choice D is incorrect Vacuoles and vesicles are membrane bound sacs involved in the transport and storage of materials that are ingested secreted, processed, or digested by the cells Vacuoles are larger than vesicles and are more likely to be found in plant cells D After birth, a number of changes occur in the circulatory system as the fetus adjusts to breathing on its own The lungs expand with air and rhythmic breathing begins Resistance in the pulmonary blood vessels decreases, causing an increase in blood flow through the lungs When the umbilical blood flow stops, blood pressure in the inferior vena cava decreases, causing a decrease in pressure in the right atrium In contrast, left atrial pressure increases due to increased blood flow from the lungs Increased left atrial pressure coupled with decreased right atrial pressure causes the foramen ovale to close In addition, the ductus arteriosus constricts and later closes permanently The ductus venosus degenerates over a period of time, completely closing in most infants three months after birth The infant begins to produce adult hemoglobin, and by the end of the first year of life, little fetal hemoglobin can be detected in the blood C If the frequency of the dominant allele is three times that of the recessive allele, then p = 3q According to HardyWeinberg equilibrium, p + q = so 3q + q =1 Solving for q we get 4q = 1; q = 0.25 and p = 0.75 Again according to Hardy-Weinberg, the frequency of the heterozygotes is equal to 2pq Substituting in our values for p and q we have the equation 2(0.75)(0.25) which equals 0.375 or 37.5% D The endoderm will develop into the epithelial linings of the digestive and respiratory tracts, parts of the liver, pancreas, thyroid, and the bladder lining Choice A is incorrect because the lens of the eyes will develop from the ectoderm Choice B is incorrect because the gonads are developed from the mesoderm Choice C is incorrect because the nervous system is developed from the ectoderm Choice E is incorrect because the connective tissue is developed from the mesoderm 10 E Platelets are cell fragments that lack nuclei and are involved in clot formation KAPLAN _ B I O L O G Y S U B J E C T T E S T Choice A, erythrocytes, are the oxygen carrying components of the blood They contain hemoglobin which can bind up to four molecules of oxygen Choice B, macrophages, carry out phagocytosis of foreign particles and bacteria, digest them, and present the fragments on their cell surface Choice C, T cells, lyse virally infected cells or secrete proteins which stimulate the development of B or other types of T cells Choice D, B cells, mature into memory cells or antibody producing cells during immune responses 11 C The thyroid hormone, thyroxine, or tetraiodothyronine, is simply an amino acid containing four atoms of iodine Another thyroid hormone, triiodothyronine, contains three atoms of iodine Both of these hormones accelerate oxidative metabolism throughout the body Thyroid-stimulating hormone (TSH) is secreted by the anterior pituitary to stimulate the thyroid gland 12 C Hypothyroidism is caused by inflammation of the thyroid or iodine deficiency Thyroid hormones are undersecreted or not secreted at all Common symptoms of hypothyroidism include a slowed heart rate and respiratory rate, fatigue, cold intolerance, and weight gain In newborns, it is termed cretinism and is characterized by mental retardation and short stature Hyperthyroidism occurs when the thyroid is over-stimulated, and symptoms often include increased metabolic rate, feelings of excessive warmth, profuse sweating, palpitations, weight loss, and protruding eyes 13 C The two ribosomal subunits are manufactured in the nucleolus, a region within the nucleus The ribosomes are the sites of protein production The fact that ribosomes are partly composed of RNA could have clued you in to the correct answer Choices A, B, D, and E are all incorrect because they refer to organelles that are composed of phospholipid membranes and protein, so they are not manufactured in the nucleus Rather, they are synthesized in regions of the cell (specifically the smooth endoplasmic reticulum and the ribosomes) other than the nucleus Choice A, the lysosome, contains hydrolytic enzymes involved in digestion Choice B, the Golgi apparatus, is a membrane-bound organelle that sorts and packages proteins made by the ribosomes Choice D, the smooth endoplasmic reticulum, is a portion of the endoplasmic reticulum that does not have ribosomes and is involved in lipid synthesis and drug detoxification Choice E, the cell membrane, is a barrier between the interior and exterior of the cell 14 E Choices A, B, and C are all true statements about capillaries Choice A is correct because a capillary has a higher hydrostatic pressure at the arteriole end and a lower hydrostatic pressure at the venule end As blood flows from arterioles to capillaries, blood pressure gradually drops due to friction between the blood and the walls of the vessels and the increase in cross-sectional areas provided by numerous capillary beds Choice B is correct as well Blood plasma in the capillaries has a higher osmotic pressure than the pressure in interstitial fluid This is a result of the greater amount of dissolved solutes in the blood plasma of the capillaries Choice C is correct because the pumping force of the heart through the blood vessels creates hydrostatic pressure Hydrostatic pressure is defined as the force per area that blood exerts on the walls of the blood vessels Again, choice E is the correct answer because choices A, B, and C are all true statements 15 A Sulfur is sometimes found in proteins but never in nucleic acids The famous Hershey-Chase experiment took advantage of this to determine whether proteins or nucleic acids carried the genetic information of the cell KAPLAN B I O L O G Y S U B J E C T T E S T The other choices are incorrect: Nucleic acids contain the elements C, H, O, N and P They are polymers of subunits called nucleotides and code all the information needed by an organism to produce proteins and replicate 16 A Any male born from that mating will receive an X chromosome from his mother and a Y from his father The X he receives will either carry fragile X syndrome or colorblindness, so he has a 50% chance of having fragile X syndrome and a 50% chance of being color blind, neither of which are phenotypically normal 17 D The cytoskeleton forms the mitotic spindle, which is responsible for separating sister chromatids during cell division It is integral in proper cell division All the other choices are true of the cytoskeleton: The cytoskeleton is composed of microtubules and microfilaments and gives the cell mechanical support, maintains its shape and functions in cell motility 18 C 32 ATP are produced by the electron transport chain and oxidative phosphorylation Ultimately, molecule of glucose will be catalyzed to produce 36 ATP (32 from oxidative phosphorylation, from the citric acid cycle, and from glycolysis) 19 C Before considering the Punnett square for the offspring, we will determine the phenotype of the parents A red eyed fly with red eyed and sepia eyed parents must be heterozygous because its sepia eyed parent can only contribute the recessive sepia allele If this heterozygous fly is crossed with a homozygous recessive (sepia) eyed fly, 1/2 the offspring will be red eyed because they will receive the red, dominant allele from the heterozygous fly The Punnett square will look like this: Red eyed parent 20 Sepia eyed r parent r R r Rr (red) Rr (red) rr (sepia) rr (sepia) B The retina develops from the ectoderm The ectoderm develops into the nervous system, the epidermis, the lens of the eye, and the inner ear The endoderm develops into the lining of the digestive tract, lungs, liver, and pancreas The mesoderm develops into the muscles, skeleton, circulatory system, gonads, and kidneys 21 D The large intestine is primarily involved in water reabsorption Salts and minerals are reabsorbed with this water, and bacteria within the large intestine produce vitamin K, which is also absorbed in the large intestine Answer choice A is incorrect because the duodenum is the anterior section of the small intestine, which connects to the posterior end of the stomach Answer choice B is incorrect because the jejunum is the second section of the small intestine It connects to the 10 _ KAPLAN _ B I O L O G Y S U B J E C T T E S T duodenum on its anterior end and to the ileum on its posterior end Answer choice C is incorrect because the stomach is primarily a food-holding organ Some small amount of protein digestion occurs there Answer choice E is incorrect because the mouth does not absorb water, but it does chew and moisten food and convert a small amount of starch to maltose through the enzyme salivary amylase 22 C Osmosis is a special type of diffusion involving water and is a form of passive transport Hypertonic means high solute and low solvent Hypotonic means high solvent and low solute Solvent always flows spontaneously from an area of high solvent concentration to an area of low solvent concentration Therefore, water will flow from a hypotonic environment to a hypertonic environment 23 A The medulla controls many vital functions, including breathing, heart rate and gastrointestinal activity Choice B is wrong because the hypothalamus controls such things as hunger, thirst, sex drive, water balance, blood pressure and temperature regulation It also plays an integral role in controlling the endocrine system Choice C is wrong because the cerebrum (usually referred to as the cerebral cortex) processes and integrates sensory input and motor responses, and is important for memory and creative thought Choice D is wrong because the cerebellum is important in coordinating muscles It aids in balance (it receives input from the inner ear), hand-eye coordination, and the timing of rapid movements Choice E is wrong because the pituitary gland, along with the hypothalamus, plays an integral role in controlling the endocrine system 24 B Skeletal muscle is responsible for voluntary movement and is innervated by the somatic nervous system A muscle is a bundle of parallel fibers Each fiber is a multinucleated cell created by the fusion of several mononucleate embryonic cells Answer choice C is incorrect because smooth muscle is responsible for involuntary action and is innervated by the autonomic nervous system It is found in the digestive tract, bladder, uterus, and blood vessel walls and possesses one centrally located nucleus Answer choice A is incorrect because cardiac muscle composes the muscle tissue of the heart These muscle fibers possess characteristics of both skeletal and smooth muscle fibers As in skeletal muscle, the cardiac muscle has a striated appearance; however, cardiac muscle cells generally have only one or two centrally located nuclei Cardiac muscle is innervated by the autonomic nervous system, which serves only to modulate its inherent beat 25 A The posterior pituitary releases two hormones; oxytocin and antidiuretic hormone (ADH, also called vasopressin) Choice B, FSH, is released by the anterior pituitary Choice C, glucagon, is released by the alpha cell of the islets of Langerhans in the pancreas Choice D, estrogen, is released by the graafian follicle within the ovary during the menstrual cycle Choice E, calcitonin, is released by the thyroid gland KAPLAN _ 11 B I O L O G Y S U B J E C T T E S T 26 C The oral cavity is where mechanical and chemical digestion of food begins Mechanical digestion is the breakdown of large food particles into smaller particles through the biting and chewing action of teeth increasing the total surface area Chemical digestion begins in the mouth when the salivary glands secrete saliva, which contains the enzyme salivary amylase, which hydrolyzes starch into simple sugars Saliva also lubricates the food to facilitate swallowing and provides a solvent for food particles The muscular tongue manipulates the food during chewing and rolls it into a ball called a bolus and pushes the bolus into the pharynx 27 C Luteinizing hormone (LH) is first released as a surge midway through the menstrual cycle This surge causes the mature follicle to burst, releasing the ovum from the ovary Following ovulation, LH induces the ruptured follicle to develop into the corpus luteum (hence the name), which then secretes estrogen and progesterone Choice A is incorrect because it is progesterone and estrogen that inhibits GnRH release (thereby inhibiting FSH and LH release, thus preventing additional follicles from maturing) Choice B is incorrect because LH is secreted by the anterior pituitary The ovary secretes estrogen and progesterone Choice D is describing the function of progesterone, not LH Choice E is describing the function of prolactin, not LH 28 D If a piece of cardiac muscle were placed in a petri dish and nourished properly, it would contract at intrinsic beat Cardiac muscle, unlike any other muscle type, is capable of depolarizing spontaneously, which causes a contraction Other muscle types require some type of stimulation to cause depolarization and contraction (usually a neurotransmitter) Choice A is incorrect because cardiac muscle is innervated by the autonomic nervous system The somatic motor system controls voluntary actions walking, running, etc Cardiac muscle is striated, eliminating choice B, and has only one or two centrally located nuclei, eliminating choice C 29 C During glycolysis, net molecules of ATP are produced by substrate-level phosphorylation, and molecules of NAD+ are reduced to form NADH Choice A is incorrect because glycolysis is an anaerobic process Thus, oxygen plays no part in glycolysis Choice B is incorrect because during glycolysis, glucose is partially oxidized, not reduced Choice D is also incorrect because two molecules of pyruvic acid are formed for each molecule of glucose that undergoes glycolysis Choice E is incorrect because pyruvic acid is produced during glycolysis, not during the Krebs cycle After pyruvic acid is produced in glycolysis, it is subsequently converted to acetyl coenzyme A, which then enters the Krebs cycle 30 B The area in the kidney with the lowest solute concentration is the cortex Filtrate that the enters the nephron travels through the proximal convoluted tubule, then through the loop of Henle, followed by the distal convoluted tubule, collecting duct, renal pelvis then out of the kidney to the bladder The convoluted tubules are within the cortex, and the loop of Henle, collecting duct and pelvis are in the medulla As filtrate travels from the cortex to the medulla, it constantly experiences an increasing concentration gradient, the purpose of which is to reabsorb water, so that the urine be concentrated 12 _ KAPLAN _ B I O L O G Y S U B J E C T T E S T Choice A is incorrect because the solute concentration within the nephron varies according to the region of the kidney through which the filtrate is traveling Choice C is incorrect because the medulla has a very high concentration gradient, which is necessary in order for an organism to produce concentrated urine Choice D is incorrect because the pelvis, which is in the medulla, has a very high concentration gradient, so that water can be reabsorbed Choice E is incorrect because epithelia does not refer to a region within the kidney 31 C The parathyroid glands are four small pea-shaped structures embedded in the posterior surface of the thyroid These glands synthesize and secrete parathyroid hormone, which together with calcitonin and vitamin D, regulates plasma Ca2+ concentration In turn, the plasma Ca2+ concentration regulates PTH secretion by means of a negative feedback mechanism PTH raises the Ca2+ concentration in the blood by increasing bone resorption and decreasing Ca2+ excretion in the kidneys In addition, PTH converts vitamin D into its active form, which stimulates intestinal calcium absorption Glucagon, choice A, stimulates the conversion of glycogen to glucose in the liver and therefore increases blood glucose Insulin, choice B, lowers blood glucose and increases storage of glycogen Aldosterone, choice D, regulates plasma levels of sodium and potassium and consequently the total extracellular water volume It causes the active reabsorption of sodium and passive reabsorption of water in the nephron ADH, choice E, stimulates water reabsorption by the kidneys by increasing the nephron’s permeability to water 32 B With no gamma globulins (antibodies), an organism cannot produce a specific immune response to pathogens Clinical manifestations of this are frequent, severe, prolonged infections by organisms of typically low pathogenicity 33 E The resting membrane potential across a nerve cell membrane depends on the physiology of two ions; Na+ and K+ The Na+/K+ pump is an active transport protein that maintains an electrochemical gradient across the membrane by pumping Na+ out and K+ in This unequal pumping causes: (1) the cell to be negative on the inside relative to the outside; (2) a high concentration of Na+ outside the cell relative to the inside; (3) a high concentration of K+ inside relative to the outside The membrane is more permeable to K+ than Na +, and it is the balance between the pump and the "leaky" membrane that determines the cell's resting potential 34 E Exhalation is generally a passive process involving elastic recoil of the lungs and relaxation of both the diaphragm and the external intercostal muscles However, during vigorous exercise, active muscle contraction assists in expiration Gas exchange is also a passive process; gases diffuse down their partial pressure gradients Inhalation is an active process requiring contraction of the diaphragm and the external intercostals 35 B Veins not have a strong pulse They are thin-walled inelastic vessels that usually conduct deoxygenated blood (the exception being the pulmonary vein) toward the heart Blood flow depends on compression by neighboring skeletal muscles rather than a smooth muscular wall lining as found in arteries Answer choice A is a correct statement, as it is a characteristic of mammals to have a four chambered heart Arteries (choice C) are thick walled, muscular elastic vessels the transport blood away from the heart This blood is usually oxygenated (except for the pulmonary arteries) The lymphatic system (choice D) an open circulatory system that transports excess interstitial fluid (lymph) to the cardiovascular system and keeps fluid levels constant Lymph enters the bloodstream at the thoracic duct, which connects to the superior vena cava The pumping chambers of the heart are called ventricles The atria are collecting chambers KAPLAN _ 13 B I O L O G Y S U B J E C T T E S T 36 B The middle ear is made of three bones; the malleus, incus, and stapes They amplify the vibrations of the tympanic membrane ("ear drum") and transmit it to the oval window, which leads to the inner ear and receptors on the auditory nerve The nose, outer ear, skeletal joints, and the larynx are all made of cartilage Cartilage is not innervated or vascularized 37 D Glucagon, secreted by the pancreatic Islet of Langerhans cells in response to a low glucose blood level, stimulates gluconeogenesis and the conversion of glycogen into glucose, thereby raising blood sugar levels Choice A is incorrect because oxytocin, which is produced by the hypothalamus and secreted by the posterior pituitary, stimulates uterine contractions during labor, and milk secretion during lactation Choice B is incorrect because calcitonin, secreted by the thyroid gland, lowers blood calcium levels Choice C is incorrect because estrogen, secreted by the ovaries, is responsible for the maintenance of female secondary sex characteristics and maintenance of the endometrium Choice E is incorrect because thyrotropin is an anterior pituitary hormone that stimulates the thyroid to release thyroxine and triiodothyronine The functions of thyroxine and triiodothyronine are to increase metabolic rate 38 D Choices B and C are correct At the arteriole end of the capillary bed the hydrostatic pressure is approximately 36 mmHg while the opposing osmotic pressure is approximately 25 mmHg The larger hydrostatic pressure forces fluid out of the capillaries At the venule end of the capillary bed, the osmotic pressure across the wall is greater than the hydrostatic pressure, which has dropped to 15 mmHg This difference tends to draw fluid into the capillaries (osmosis) Hence, most of the fluid is forced out of the capillaries at the arteriole end, and is reabsorbed by the capillaries at the venule end [Note: the specific pressures discussed above need not be memorized; understand the relative values at both ends of the capillary] 39 E Aldosterone is produced by the adrenal cortex and stimulates both the reabsorption of Na+ from the collecting duct, and the secretion of K+ (it causes Na+/K+ pumps to be turned on at the distal convoluted tubule) The Na+ reabsorption pulls water with it, leading to a rise in blood volume, and hence a rise in blood pressure and the production of more concentrated urine Its release is stimulated by angiotensin II, which was formed as a result of the action of renin (the renin-angiotensin system) Answer choice E is NOT true about aldosterone, so is the correct answer choice Vasopressin (ADH; antid diuretic hormone) is produced by the hypothalamus and stored in the posterior pituitary It increases water reabsorption by opening water channels in the nephron (as opposed to the indirect action of aldosterone which increases salt reabsorption) 40 A Lymph nodes are swellings along lymph vessels containing phagocytic cells (leukocytes) that filter the lymph, removing and destroying foreign particles and pathogens The liver breaks down hemoglobin and use the components to produce bile salts Glucagon, produced by the pancreas, increases the blood concentration of glucose Lymphatic fluid absorbs fat and fat soluble vitamins and does not absorb amino acids from the digestive tract Hemoglobin, found in red blood cells, carries oxygen 14 _ KAPLAN ... _ B I O L O G Y S U B J E C T T E S T Biology Subject Test What is the principal function of NaHCO3? A B C D Dissolves CO2 better Inactivates... B I O L O G Y S U B J E C T T E S T BIOLOGY SUBJECT TEST ANSWER KEY C D 17 D 25 A 33 E C 10 E 18 C 26 C 34 E C 11 C 19 C 27 C 35 B C 12 C 20... and kidneys 21 D The large intestine is primarily involved in water reabsorption Salts and minerals are reabsorbed with this water, and bacteria within the large intestine produce vitamin K, which