Table of Contents How to Use this Book Introduction to the MCAT Part I - Review Chapter - The Cell Practice Questions Chapter - Enzymes Practice Questions Chapter - Cellular Metabolism Practice Questions Chapter - Reproduction Practice Questions Chapter - Embryology Practice Questions Chapter - The Musculoskeletal System Practice Questions Chapter - Digestion Practice Questions Chapter - Respiration Practice Questions Chapter - The Cardio vascular System Practice Questions Chapter 10 - The Immune System Practice Questions Chapter 11 - Homeostasis Practice Questions Chapter 12 - The Endocrine System Practice Questions Chapter 13 - The Nervous System Practice Questions Chapter 14 - Genetics Practice Questions Chapter 15 - Molecular Genetics Practice Questions Chapter 16 - Evolution Practice Questions Chapter 17 - High-Yield Problem Solving Guide for Biology Part II - Practice Sections Practice Section Practice Section Practice Section Answers and Explanations Glossary Related Titles MCAT ® BIOLOGY REVIEW KAPLAN’S EXPERT MCAT TEAM Kaplan has been preparing premeds for the MCAT for more than 40 years In the past 15 years alone, we’ve helped more than 400,000 students prepare for this important exam and improve their chances for medical school admission Marilyn Engle MCAT Master Teacher; Teacher Trainer; Kaplan National Teacher of the Year, 2006; Westwood Teacher of the Year, 2007; Westwood Trainer of the Year, 2007; Encino Trainer of the Year, 2005 John Michael Linick MCAT Teacher; Boulder Teacher of the Year, 2007; Summer Intensive Program Faculty Member Dr Glen Pearlstein MCAT Master Teacher; Teacher Trainer; Westwood Teacher of the Year, 2006 Matthew B Wilkinson MCAT Teacher; Teacher Trainer; Lone Star Trainer of the Year, 2007 Thanks to Jason Baserman, Jessica Brookman, Da Chang, John Cummins, David Elson, Jeff Koetje, Alex Macnow, Andrew Molloy, Josh Rohrig, and Amjed Saffarini ABOUT SCIENTIFIC AMERICAN As the world’s premier science and technology magazine, and the oldest continuously published magazine in the United States, Scientific American is committed to bringing the most important developments in modern science, medicine, and technology to 3.5 million readers worldwide in an understandable, credible, and provocative format Founded in 1845 and on the “cutting edge” ever since, Scientific American boasts over 140 Nobel laureate authors, including Albert Einstein, Francis Crick, Stanley Prusiner, and Richard Axel Scientific American is a forum where scientific theories and discoveries are explained to a broader audience Scientific American published its first foreign edition in 1890 and, in 1979, was the first Western magazine published in the People’s Republic of China Today, Scientific American is published in 17 foreign language editions with a total circulation of more than million worldwide Scientific American is also a leading online destination (www.ScientificAmerican.com), providing the latest science news and exclusive features to more than million unique visitors monthly The knowledge that fills our pages has the power to inspire, to spark new ideas, paradigms, and visions for the future As science races forward, Scientific American continues to cover the promising strides, inevitable setbacks and challenges, and new medical discoveries as they unfold How to Use this Book Kaplan MCAT Biology , along with the other four books in our MCAT Review series, brings the Kaplan classroom experience to you—right in your home, at your convenience This book offers the same Kaplan content review, strategies, and practice that make Kaplan the #1 choice for MCAT prep All that’s missing is the teacher To guide you through this complex content, we’ve consulted our best MCAT instructors to call out Key Concept, to offer Bridge to better understanding of the material, and Mnemonic devices to assist in learning retention When you see these sidebars, you will know you’re getting the same insight and knowledge that classroom students receive in person Look for these as well as references to the Real World and MCAT expertise callouts throughout the book HIGH-YIELD MCAT REVIEW Following the content sction, you will find a High-Yield Questions section These questions tackle the most frequently tested topics found on the MCAT For each type of problem, you will be provided with a stepwise technique for solving the question, as well as important directional points on how to solve it—specifically for the MCAT Our experts have again called out the Key Concepts , which show you which terms to review Next, the Takeaways box offers a concise summary of the problem-solving approach best used Things to Watch Out For points out any caveats to the approach discussed, which can lead to wrong answer choices Finally, Similar Questions allows you to practice the stepwise technique on analogous, open-ended questions STAR RATING The star rating is a Kaplan-exclusive system to help you focus your studies, using a 6-star scale Two factors are considered when determining the rating for each topic: the “learnability” of the topic—or how easy it is to master —and the frequency with which it appears on the MCAT exam For example, a topic that presents relatively little difficulty to master and appears with relatively high frequency on the MCAT would receive a higher star rating (e.g., or stars) than a topic which is very difficult to master and appears less frequently on the test The combination of these two factors represented by the star rating will help you prioritize and direct your MCAT studies We’re confident that this guide and our award-winning instructors can help you achieve your goals of MCAT success and admission to med school Good luck! Introduction to the MCAT The Medical College Admission Test (MCAT) is different from any other test you’ve encountered in your academic career It’s not like the knowledge-based exams from high school and college, where emphasis was on memorizing and regurgitating information Medical schools can assess your academic prowess by looking at your transcript The MCAT isn’t even like other standardized tests you may have taken, where the focus was on proving your general skills Medical schools use MCAT scores to assess whether you possess the foundation upon which to build a successful medical career Though you certainly need to know the content to well, the stress is on thought process, because the MCAT is above all else a critical thinking test That’s why it emphasizes reasoning, analytical thinking, reading comprehension, data analysis, writing, and problem-solving skills Though the MCAT places more weight on your thought process, you must have a strong grasp of the required core knowledge The MCAT may not be a perfect gauge of your abilities, but it is a relatively objective way to compare you with students from different backgrounds and undergraduate institutions The MCAT’s power comes from its use as an indicator of your abilities Good scores can open doors Your power comes from preparation and mindset because the key to MCAT success is knowing what you’re up against That’s where this section of this book comes in We’ll explain the philosophy behind the test, review the sections one by one, show you sample questions, share some of Kaplan’s proven methods, and clue you in to what the test makers are really after You’ll get a handle on the process, find a confident new perspective, and achieve your highest possible scores Embryonic hollow tube that subsequently gives rise to the central nervous system Neuron A cell that conducts electrical impulses; the functional unit of the nervous system Neurotransmitter A chemical agent released into the synaptic cleft by the synaptic bouton of a neuron Binds to receptor sites on postsynaptic neurons or effector membranes to alter activity Niche The role of a given organism within the environment, including its interactions with other organisms and with the physical environment Nitrogen fixation Incorporation of atmospheric nitrogen into inorganic nitrogen compounds Performed by bacteria Nodes of Ranvier Points on a myelinated axon that are not covered by myelin Nondisjunction Failure of homologous chromosomes to separate during meiosis Noradrenaline See norepinephrine Norepinephrine A hormone secreted by the adrenal medulla that stimulates the fight-or-flight response; also a neurotransmitter Notochord A supportive rod running just ventral to the neural tube in lower chordates and in vertebrate embryos Nuclear membrane Double membrane enveloping the nucleus, interrupted periodically by pores; found in eukaryotic cells only Nucleic acid Polymer of nucleotides (e.g., DNA and RNA) Nucleoid The region in prokaryotic cells where the chromosome is located Nucleolus Dense body visible in a nondividing nucleus Site of ribosomal RNA synthesis Nucleosome Packaging unit of DNA in eukaryotic cells consisting of DNA and histone proteins complexed together Nucleotide An organic molecule composed of three subunits: a five-carbon sugar, a phosphate group, and a purine or a pyrimidine (nitrogenous base) The basic subunits of DNA and RNA Nucleus The eukaryotic membrane-bound organelle that contains the cell’s chromosomes Oocyte An undifferentiated cell that undergoes meiosis to produce an egg cell (ovum) Oogenesis Gametogenesis in the ovary leading to the formation of mature ova Operator A site on DNA that interacts with a repressor protein, regulating transcription of an operon Operon A segment of DNA consisting of a promoter, operator, and structural genes The structural genes code for products of a specific biochemical pathway; their transcription is regulated by a repressor protein Organ A body part composed of a group of tissues that form a functional and structural unit Organelle Any specialized cytoplasmic structure Osmosis The diffusion of water across a semipermeable membrane from a region of low solute concentration to a region of high solute concentration Ovary The female egg-producing gonad Oviduct (Fallopian tube) The tube leading from the outer extremity of the ovary to the uterus; generally, the site of fertilization Ovulation The release of the mature ovum from the ovarian follicle Ovum The female gamete; egg cell Oxidation The loss of electrons or hydrogen from an atom, ion, or molecule; the addition of oxygen to an atom, ion, or molecule Oxidative phosphorylation The synthesis of ATP using the energy released from the reactions of the electron transport chain Oxygen debt The amount of oxygen needed to reconvert lactic acid to pyruvate following strenuous exercise of muscle tissue Pancreas A gland that secretes digestive enzymes into the duodenum via a duct and synthesizes and secretes the hormones insulin, glucagon, and somatostatin; located between the stomach and the duodenum Parasympathetic nervous system The subdivision of the autonomic nervous system involved in rest or homeostasis; it is antagonistic to the sympathetic nervous system Parathyroids Two pairs of glands located on the thyroid that secrete hormones that regulate calcium and phosphorous metabolism Parthenogenesis A form of asexual reproduction yielding progeny without fertilization of the ovum by spermatozoa Passive immunity Immunity conferred by the transfer or injection of previously formed antibodies Passive transport The movement of a substance across a membrane without the expenditure of energy Patella The bone of the kneecap Pathogen A disease-causing agent Pepsin A stomach enzyme that cleaves peptide bonds of proteins Peptide bond The bond between two amino acids that results from a condensation reaction between the carboxyl end of one amino acid and the amino end of the other Peripheral nervous system Includes all neurons outside the central nervous system, including sensory and motor neurons; it is subdivided into somatic and autonomic nervous systems Compare central nervous system Peristalsis Rhythmic waves of muscular contraction that move a substance through a tube (e.g., food through the digestive tract) Peritoneum Membrane lining of the abdomen and pelvis that also covers the visceral organs Permeable Allowing solutes to pass through; a term usually applied to biological membranes Phagocytosis A type of endocytosis in which large particles are engulfed by a cell Phenotype The physical manifestation of an organism’s genotype Phylogeny The evolutionary history of related organisms Physiology The study of the life processes of plants or animals Pinocytosis A type of endocytosis in which small particles or liquid are engulfed by a cell Pituitary The bilobed endocrine gland that lies just below the hypothalamus; because many of its hormones regulate other endocrine glands, it is known as the “master gland.” Placenta The structure formed by the wall of the uterus and the chorion of the embryo containing a network of capillaries through which exchange between maternal and fetal circulation occurs Plasma The fluid component of blood containing dissolved solutes, minus the red blood cells Plasma cells Derived from B-lymphocytes; have the ability to produce and secrete antibodies Platelets Small, enucleated disk-shaped blood cells that play an important role in blood clotting Polar body A small, nonfunctional haploid cell created during oogenesis Polypeptide A polymer composed of many amino acids linked together by peptide bonds Polyploid A cell or an organism that has more than two alleles per trait Polyribosome A group of ribosomes attached to a strand of mRNA, simultaneously translating it Population A group of organisms of the same species living together in a given location Portal system A circuit of blood in which there are two capillary beds in tandem connected by an artery or vein Posterior Pertaining to the rear, or tail end Compare anterior Potential An electrical difference or gradient between two points or structures (e.g., across axon membranes) Progesterone A hormone secreted by the corpus luteum and the placenta; it prepares the uterine wall for implantation and maintains the thickened wall during pregnancy Prokaryote Cell lacking a nuclear membrane and membrane-bound organelles, such as a bacterium Compare eurkaryote Promoter A specific site on the DNA strand to which RNA polymerase attaches to initiate operon transcription Prophase The stage of mitosis or meiosis during which the DNA strands condense to form visible chromosomes; during prophase I of meiosis, homologous chromosomes align Prostate A gland in the mammalian male that secretes alkaline seminal fluid Prosthetic group A nonpolypeptide unit tightly bound to an enzyme that is essential for that enzyme’s activity Proteins Complex organic polymers of amino acids linked together by peptide bonds Proximal Closer to some point of reference, that point usually being the midline of the body (e.g., the elbow is proximal to the hand) Purines Double-ringed nitrogenous bases such as adenine and guanine Purkinje fibers The terminal fibers of the heart’s conducting system; located in the walls of ventricles Pyloric sphincter The valve that regulates the flow of chyme from the stomach into the small intestine Pyrimidines Single-ringed nitrogenous bases such as cytosine, thymine, and uracil Recessive An allele that does not express its phenotype in the presence of a dominant allele Compare dominant codominance, Recombination New gene combinations achieved by sexual reproduction or crossing over in eukaryotes and by transformation, transduction, or conjugation in prokaryotes Reduction The process whereby an atom, ion, or molecule gains electrons or hydrogens; the loss of oxygen from an atom, ion, or molecule Reflex An involuntary nervous pathway consisting of sensory neurons, interneurons, motor neurons, and effectors; it occurs in response to a specific stimulus Refractory period The period of time following an action potential during which the neuron is incapable of depolarization Regeneration A type of asexual reproduction in which an organism replaces lost body parts Releasing hormones Proteins synthesized and secreted by the hypothalamus that stimulate the pituitary to synthesize and release its hormones Renal Of or pertaining to the kidneys Repressor In an operon, the protein that prevents attachment of RNA polymerase to the promoter by binding to the operator It is coded for by the regulator Respiration (1) Cellular respiration: The series of oxygen-requiring biochemical reactions that lead to ATP synthesis (2) External respiration: The inhalation and exhalation of gases and their exchange at a respiratory surface Resting potential The electrical potential of a neuron at rest, approximately 70mV across the axon membrane Retina The innermost tissue layer of the eye; the sensory cells (rods and cones) are located there Retrovirus An RNA virus that contains the enzyme reverse transcriptase, which transcribes RNA into DNA Rh factor An antigen on a red blood cell whose presence or absence is indicated by a + or–, respectively, in blood type notation Ribosome Organelle composed of RNA and protein; it translates mRNA during polypeptide synthesis RNA (Ribonucleic acid) Nucleic acid composed of monomers consisting of the five-carbon sugar ribose, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil); functions in protein synthesis Sarcolemma Muscle cell membrane capable of propagating action potentials Sarcomere The functional contractile unit of striated muscle Sarcoplasmic reticulum The endoplasmic reticulum of a muscle cell; it envelops myofibrils Selection pressure A force, resulting from natural selection parameters, that causes changes within the gene pool of a population Semen Fluid released during ejaculation consisting of sperm cells suspended in seminal fluid Seminal vesicle A gland found in mammalian males that produces seminal fluid Sensory neuron See afferent neuron Sex-linked gene A gene located only on a sex chromosome; such genes exhibit different inheritance patterns in males and females Sexual reproduction Any reproductive process that involves the fusion of gametes resulting in the passage of combined genetic information to offspring Sinoatrial node (SA node, pacemaker) A group of cells on the surface of the right atrium of the heart; it initiates and controls cardiac muscle contraction Somatic cells Autosomal cells; all cells in the body except germ cells and gametes Species A taxonomic classification applied to organisms of common ancestry who possess the ability to produce fertile offspring Sperm The mature male gamete or sex cell Spermatogenesis Gametogenesis in the testes leading to sperm formation Sphincter A ring-shaped muscle that closes and opens a tube (e.g., the pyloric sphincter) Spindle A structure within dividing cells composed of microtubules; it is involved in the separation of chromosomes during mitosis and meiosis Spore An asexual reproductive cell that can endure extreme environmental conditions and develop into an adult organism when conditions become favorable Stem cells Nondifferentiated, rapidly dividing cells in the marrow of long bones that differentiate into red and white blood cells Steroids Four-ringed organic lipid molecules that make up many hormones and vitamins Stimulus Any change in an organism’s internal or external environment that changes the organism’s activity Sympathetic nervous system The subdivision of the autonomic nervous system that produces the “fight-or-flight” response Compare parasympathetic nervous system Synapse The junction between two neurons into which neurotransmitters are released Synapsis The pairing of homologous chromosomes during prophase I of meiosis Syngamy The union of gametes Systole The period of heart contraction during which the ventricles contract and pump blood into the aorta and pulmonary arteries Compare diastole Taxonomy The classification of organisms according to their evolutionary relationships TCA cycle See Krebs cycle Telencephalon Anterior portion of the forebrain Telophase The final stage of mitosis or meiosis during which the chromosomes uncoil, nuclear membranes reform, and cytokinesis occurs Template A molecule that directs the synthesis of another molecule by acting as a model or pattern (e.g., mRNA is the template for protein synthesis) Tendon A fibrous connective tissue that connects a bone to a muscle Test cross A cross between an organism showing a dominant trait and an organism showing a recessive trait to determine whether the former organism is homozygous or heterozygous for that trait Testis The male sperm-producing organ; also secretes testosterone Tetanus Sustained muscle contraction that results from continuous stimulation Tetrad A pair of homologous chromosomes synapsing during prophase I of meoisis Each chromosome consists of two sister chromatids; thus, each tetrad consists of four chromatids Thalamus The relay center between the brainstem and the cerebral cortex; located in the posterior part of the forebrain Thoracic duct The lymphatic vessel that empties lymph into the bloodstream Threshold The lowest magnitude of stimulus strength that will induce a response Thrombin An enzyme that participates in blood clotting; it converts fibrinogen into fibrin Thymine A pyrimidine present in DNA but not in RNA; it forms hydrogen bonds with adenine Thymus A ductless gland in the upper chest region of vertebrates; it functions in the development of the immune system Thyroid A vertebrate endocrine gland located in the neck; it synthesizes thyroxine Thyroxine A hormone produced and released by the thyroid that regulates metabolic rate Tissue A mass of similar cells and support structures organized into a functional unit Tonus A continuous state of muscle contraction Trachea The tube that connects the pharynx to the bronchi; the windpipe Transcription The synthesis of RNA molecules from a DNA template Transduction The transposition of genetic material from one organism to another by a virus See bacteriaphage Transfer RNA (tRNA) RNA molecules that bind to specific amino acids and carry them to ribosome/mRNA complexes during protein synthesis Transformation Uptake and incorporation of “naked” DNA by a recipient bacterial cell Translation The process by which protein synthesis is directed by an mRNA nucleotide sequence Uracil A pyrimidine found in RNA but not DNA; it forms hydrogen bonds with adenine Urea A nitrogenous waste product produced in the liver from ammonia and CO Ureter The duct that carries urine from the kidneys to the bladder Urethra The tube that leads from the bladder to the exterior Urine Liquid waste resulting from the filtration, reabsorption, and secretion of filtrate in the nephron Uterus Organ in the mammalian female reproductive system that is the site of embryonic development Vaccine A solution of fractionated, dead, or attenuated live pathogenic material that is introduced into an individual for the purpose of stimulating a primary immune response or “boosting” a previously produced anamnestic state Vacuole A membrane-bound organelle in which water-soluble nutrients and wastes are stored Vagus nerve The tenth cranial nerve; it innervates the pharynx, larynx, heart, lungs, and abdominal viscera Responsible for maintaining homeostatic activity Vas deferens The tube carrying sperm from the testis to the urethra in mammalian males Vasopressin See antidiuretic hormone Vena cavae Two large veins, the superior vena cava and the inferior vena cava, that return deoxygenated blood from the periphery to the heart (right atrium) Ventral Pertaining to the undersurface or front surface of an organism Ventricles The chambers of the heart that pump blood into pulmonary and systemic circulation Vertebrate Member of phylum chordata possessing a backbone composed of vertebrae (member of subphylum vertebrata) Compare invertebrate Vestigial Referring to an organ or limb that has no apparent function now but was functional at some time in the organism’s evolutionary past Villus A small projection from the wall of the small intestine that increases the surface area for digestion and absorption Virus A tiny, organism-like particle composed of protein-encased nucleic acid; viruses are obligate parasites Vitamin An organic nutrient that an organism cannot produce itself and that is required by the organism in small amounts to aid in proper metabolic functioning; vitamins often function as cofactors for enzymes White matter The portion of the central nervous system consisting primarily of myelinated axons Compare gray matter Wild type A genetics term for the phenotype characteristic of the majority of individuals in a particular species X chromosome The female sex chromosome Y chromosome The male sex chromosome Zygote The diploid (2N) cell that results from the fusion of two haploid (N) gametes Zymogen An inactive enzyme precursor that is converted into an active enzyme Related Titles Kaplan MCAT Biology Review* Kaplan MCAT General Chemistry Review* Kaplan MCAT Organic Chemistry Review* Kaplan MCAT Physics Review* Kaplan MCAT Verbal Reasoning and Writing Review* Kaplan MCAT Premier Kaplan MCAT 45 MCAT Flashcards Get into Medical School* Med School Rx* Applications for iPhone MCAT Comprehensive Flashcards MCAT Review Notes *Also available in eBook format MCAT® is a registered trademark of the American Association of Medical Colleges, which neither sponsors nor endorses this product This publication is designed to provide accurate and authoritative information in regard to the subject matter covered It is sold with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional service If legal advice or other expert assistance is required, the services of a competent professional should be sought © 2010 by Kaplan, Inc All rights reserved under International and Pan-American Copyright Conventions By payment of the required fees, you have been granted the non-exclusive, non-transferable right to access and read the text of this eBook on screen No part of this text may be reproduced, transmitted, downloaded, decompiled, reverse engineered, or stored in or introduced into any information storage and retrieval system, in any form or by any means, whether electronic or mechanical, now known or hereinafter invented, without the express written permission of the publisher eISBN : 978-1-60714-939-2 Published by Kaplan Publishing, a division of Kaplan, Inc Liberty Plaza, 24th Floor New York, NY 10006 10 Kaplan Publishing books are available at special quantity discounts to use for sales promotions, employee premiums, or educational purposes For more information or to purchase books, please call the Simon & Schuster special sales department at 866-506-1949