MCAT Biology and Biochemistry: New for MCAT 2015 (2014)

Chapter 1. MCAT 2015 Basics


So … you want to be a doctor. If you’re like most premeds, you’ve wanted to be a doctor since you were pretty young. When people asked you what you wanted to be when you grew up, you always answered “a doctor.” You had toy medical kits, bandaged up your dog or cat, and played “hospital.” You probably read your parents’ home medical guides for fun.

When you got to high school you took the honors and AP classes. You studied hard, got straight A’s (or at least really good grades!), and participated in extracurricular activities so you could get into a good college. And you succeeded!

At college you knew exactly what to do. You took your classes seriously, studied hard, and got a great GPA. You talked to your professors and hung out at office hours to get good letters of recommendation. You were a member of the premed society on campus, volunteered at hospitals, and shadowed doctors. All that’s left to do now is get a good MCAT score.

Just the MCAT.

Just the most confidence-shattering, most demoralizing, longest, most brutal entrance exam for any graduate program. At about 7.5 hours (including breaks), the MCAT tops the list … even the closest runners up, the LSAT and GMAT, are only about 4 hours long. The MCAT tests significant science content knowledge along with the ability to think quickly, reason logically, and read comprehensively, all under the pressure of a timed exam.

The path to a good MCAT score is not as easy to see as the path to a good GPA or the path to a good letter of recommendation. The MCAT is less about what you know, and more about how to apply what you know … and how to apply it quickly to new situations. Because the path might not be so clear, you might be worried. That’s why you picked up this book.

We promise to demystify the MCAT for you, with clear descriptions of the different sections, how the test is scored, and what the test experience is like. We will help you understand general test-taking techniques as well as provide you with specific techniques for each section. We will review the science content you need to know as well as give you strategies for the Critical Analysis and Reasoning Skills (CARS) section. We’ll show you the path to a good MCAT score and help you walk the path.

After all … you want to be a doctor. And we want you to succeed.


Most test-takers approach the MCAT as though it were a typical college science test, one in which facts and knowledge simply need to be regurgitated in order to do well. They study for the MCAT the same way they did for their college tests, by memorizing facts and details, formulas and equations. And when they get to the MCAT they are surprised … and disappointed.

It’s a myth that the MCAT is purely a content-knowledge test. If medical school admission committees want to see what you know, all they have to do is look at your transcripts. What they really want to see, though, is how you think. Especially, how you think under pressure. And that’s what your MCAT score will tell them.

The MCAT is really a test of your ability to apply basic knowledge to different, possibly new, situations. It’s a test of your ability to reason out and evaluate arguments. Do you still need to know your science content? Absolutely. But not at the level that most test-takers think they need to know it. Furthermore, your science knowledge won’t help you on the Critical Analysis and Reasoning Skills (CARS) section. So how do you study for a test like this?

You study for the science sections by reviewing the basics and then applying them to MCAT practice questions. You study for the CARS section by learning how to adapt your existing reading and analytical skills to the nature of the test (more information about the CARS section can be found in MCAT Critical Analysis and Reasoning Skills Review).

The book you are holding will review all the relevant MCAT Biology and Biochemistry content you will need for the test, and a little bit more. It includes hundreds of questions designed to make you think about the material in a deeper way, along with full explanations to clarify the logical thought process needed to get to the answer. It also comes with access to three full-length online practice exams to further hone your skills: see below.


In addition to the review material you’ll find in this book, there is a wealth of practice content available online at There you’ll find:

•   3 full-length practice MCATs

•   Useful information about taking the MCAT and applying to medical school

To register your book, go to You’ll see a welcome page where you can register your book by its ISBN number (found on the back cover above the barcode). Set up an account using this number and your email address. Then you can access all of your online content.



The MCAT is a computer-based test (CBT) that is not adaptive. Adaptive tests base your next question on whether or not you’ve answered the current question correctly. The MCAT is linear, or fixed-form, meaning that the questions are in a predetermined order and do not change based on your answers. However, there are many versions of the test, so that on a given test day, different people will see different versions. The following table highlights the features of the MCAT exam.


Online via Begins as early as six months prior to test date; available up until week of test (subject to seat availability).

Testing Centers

Administered at small, secure, climate-controlled computer testing rooms.


Photo ID with signature, electronic fingerprint, electronic signature verification, assigned seat.


None. Test administrator checks examinee in and assigns seat at computer. All testing instructions are given on the computer.

Frequency of Test

14 times per year distributed over January, March, April, May, June, July, August, and September.


Exclusively computer-based. NOT an adaptive test.

Length of Test Day

7.5 hours


Optional 10-minute breaks between sections, with a longer break for lunch.

Section Names

1. Chemical and Physical Foundations of Biological Systems (Chem/Phys)

2. Critical Analysis and Reasoning Skills (CARS)

3. Biological and Biochemical Foundations of Living Systems (Bio/Biochem)

4. Psychological, Social, and Biological Foundations of Behavior (Psych/Soc)

Number of Questions and Timing

59 Chem/Phys questions, 95 minutes

53 CARS questions, 90 minutes

59 Bio/Biochem questions, 95 minutes

59 Psych/Soc questions, 95 minutes


Test is scaled. Several forms per administration.

Allowed/ Not allowed

No timers/watches. No ear plugs. Noise reduction headphones available. Scratch paper and pencils given at start of test and taken at end of test. Locker or secure area provided for personal items.

Results: Timing and Delivery

Approximately 30 days. Electronic scores only, available online through AAMC login. Examinees can print official score reports.

Maximum Number of Retakes

Can be taken a maximum of three times per year, but an examinee can be registered for only one date at a time.


Registration for the exam is completed online at The AAMC opens registration for a given test date at least two months in advance of the date, often earlier. It’s a good idea to register well in advance of your desired test date to make sure that you get a seat.


There are four sections on the MCAT exam: Chemical and Physical Foundations of Biological Systems (Chem/Phys), Critical Analysis and Reasoning Skills (CARS), Biological and Biochemical Foundations of Living Systems (Bio/Biochem), and Psychological, Social, and Biological Foundations of Behavior (Psych/Soc). All sections consist of multiple-choice questions.

Most questions on the MCAT (approximately 3/4 of the science sections, all 53 in the CARS section) are passage-based, and each section of the test will have about 9–10 passages. A passage consists of a few paragraphs of information on which several following questions are based. In the science sections, passages often include equations or reactions, tables, graphs, figures, and experiments to analyze. CARS passages come from literature in social sciences, humanities, ethics, philosophy, cultural studies, and population health, and do not test content knowledge in any way.

Some questions in the science sections are freestanding questions (FSQs). These questions are independent of any passage information. These questions appear in several groups of about four to five questions, and are interspersed throughout the passages. About 1/4 of the questions in the sciences sections are freestanding, and the remainder are passage-based.

Each section on the MCAT is separated by either a 10-minute break or a longer lunch break.



Test Center Check-In

Variable, can take up to 40 minutes if center is busy.


10 minutes

Chemical and Physical Foundations of Biological Systems

95 minutes


10 minutes

Critical Analysis and Reasoning Skills

90 minutes

Lunch Break

May be 30−45 minutes

Biological and Biochemical Foundations of Living Systems

95 minutes


10 minutes

Psychological, Social, and Biological Foundations of Behavior

95 minutes

Void Option

5 minutes


10 minutes

The survey includes questions about your satisfaction with the overall MCAT experience, including registration, check-in, etc., as well as questions about how you prepared for the test.


The MCAT is a scaled exam, meaning that your raw score will be converted into a scaled score that takes into account the difficulty of the questions. There is no guessing penalty. Because different versions of the test have varying levels of difficulty, the scale will be different from one exam to the next. Thus, there is no “magic number” of questions to get right in order to get a particular score. Plus, some of the questions on the test are considered “experimental” and do not count toward your score; they are just there to be evaluated for possible future inclusion in a test.

At the end of the test (after you complete the Psychological, Social, and Biological Foundations of Behavior section), you will be asked to choose one of the following two options, “I wish to have my MCAT exam scored” or “I wish to VOID my MCAT exam.” You have five minutes to make a decision, and if you do not select one of the options in that time, the test will automatically be scored. If you choose the VOID option, your test will not be scored (you will not now, or ever, get a numerical score for this test), medical schools will not know you took the test, and no refunds will be granted. You cannot “unvoid” your scores at a later time.

So, what’s a good score? If your GPA is on the low side, you’ll need higher MCAT scores to compensate, and if you have a strong GPA, you can get away with lower MCAT scores. But the reality is that your chances of acceptance depend on a lot more than just your MCAT scores. It’s a combination of your GPA, your MCAT scores, your undergraduate coursework, letters of recommendation, experience related to the medical field (such as volunteer work or research), extracurricular activities, your personal statement, etc. Medical schools are looking for a complete package, not just good scores and a good GPA.


CBT Tools

There are a number of tools available on the test, including highlighting, strike-outs, the Mark button, the Review button, the Exhibit button, and of course, scratch paper. The following is a brief description of each tool.

1)   Highlighting: This is done in passage text (including table entries and some equations, but excluding figures and molecular structures) by clicking and dragging the cursor over the desired text. To remove the highlighted portion, just click over the highlighted text. Note that highlights DO NOT persist once you leave the passage.

2)   Strike-outs: This is done on the various answer choices by clicking over the answer choice that you wish to eliminate. As a result, the entire set of text associated with that answer choice is crossed out. The strike-out can be removed by clicking again. Note that you cannot strike-out figures or molecular structures, and strike-outs DO persist after leaving the passage.

3)   Mark button: This is available for each question and allows you to flag the question as one you would like to review later if time permits. When clicked, the “Mark” button turns red and says “Marked.”

4)   Review button: This button is found near the bottom of the screen, and when clicked, brings up a new screen showing all questions and their status (either “answered,” “unanswered,” or “marked”). You can then choose one of three options: “review all,” “review unanswered,” or “review marked.” You can only review questions in the section of the MCAT you are currently taking, but this button can be clicked at any time during the allotted time for that section; you do NOT have to wait until the end of the section to click it.

5)   Exhibit button: Clicking this button will open a periodic table. Note that the periodic table is originally large, covering most of the screen. However, this window can be resized to see the questions and a portion of the periodic table at the same time. The table text will not decrease, but scroll bars will appear on the window so you can center the section of the table of interest in the window.

6)   Scratch paper: You will be given four pages (8 faces) of scratch paper at the start of the test. While you may ask for more at any point during the test, your first set of paper will be collected before you receive fresh paper. Scratch paper is only useful if it is kept organized; do not give in to the tendency to write on the first available open space! Good organization will be very helpful when/if you wish to review a question. Indicate the passage number in a box near the top of your scratch work, and indicate which question you are working on in a circle to the left of the notes for that question. Draw a line under your scratch work when you change passages to keep the work separate. Do not erase or scribble over any previous work. If you do not think it is correct, draw one line through the work and start again. You may have already done some useful work without realizing it.


Since the MCAT is a timed test, you must keep an eye on the timer and adjust your pacing as necessary. It would be terrible to run out of time at the end to discover that the last few questions could have been easily answered in just a few seconds each.

If you complete every question, in the science sections you will have about one minute and thirty-five seconds (1:35) per question, and in the CARS section you will have about one minute and forty seconds per question (1:40).

When starting a passage in the science sections, make note of how much time you will allot for it, and the starting time on the timer. Jot down on your scratch paper what the timer should say at the end of the passage. Then just keep an eye on it as you work through the questions. If you are near the end of the time for that passage, guess on any remaining questions, make some notes on your scratch paper (remember that highlighting disappears), Mark the questions, and move on. Come back to those questions if you have time.

For the CARS section, one important thing to keep in mind is that most people will maximize their score by not trying to complete every question, or every passage, in the section. A good strategy for a majority of test takers is to complete all but one of the passages, and randomly guess on that last one. This allows you to have good accuracy on the passages you complete, and to maximize your total percent correct in the section as a whole. To complete all but one of the passages, you should spend about 10 minutes on each passage. This is an approximation, of course—you should spend a bit more time on difficult passages or passages with more questions, and a bit less on easier passages or passages with fewer questions.

To help maximize your number of correct answer choices in any section, do the questions and passages within that section in the order you want to do them in. Skip over the more difficult passages your first time through the section (Mark the first question of the passage and randomly guess on all the questions before moving on), and work the passages you feel most comfortable with first.

Process of Elimination

Process of elimination (POE) is probably the most useful technique you have to tackle MCAT questions. Since there is no guessing penalty, POE allows you to increase your probability of choosing the correct answer by eliminating those you are sure are wrong. If you are guessing between a couple of choices, use the CBT tools to your advantage:

1)   Strike out any choices that you are sure are incorrect or that do not address the issue raised in the question.

2)   Jot down some notes on your scratch paper to help clarify your thoughts if you return to the question.

3)   Use the “Mark” button to flag the question for review at a later time. (Note, however, that in the CARS section, you generally should not be returning to rethink questions once you have moved on to a new passage.)

4)   Do not leave it blank! If you are not sure and you have already spent more than 60 seconds on that question, just pick one of the remaining choices. If you have time to review it at the end, you can always debate the remaining choices based on your previous notes.

5)   Special Note: if three of the four answer choices have been eliminated, the remaining choice must be the correct answer. Don’t waste time pondering why it is correct, just click it and move on. The MCAT doesn’t care if you truly understand why it’s the right answer, only that you have the right answer selected.

6)   More subject-specific information on techniques will be presented in the next chapter.


Remember, there is NO guessing penalty on the MCAT. NEVER leave a question blank!


In the science sections of the MCAT, the questions fall into one of three main categories.

1)   Memory questions: These questions can be answered directly from prior knowledge and represent about 25 percent of the total number of questions.

2)   Explicit questions: These questions are those for which the answer is explicitly stated in the passage. To answer them correctly, for example, may just require finding a definition, or reading a graph, or making a simple connection. Explicit questions represent about 35 percent of the total number of questions.

3)   Implicit questions: These questions require you to apply knowledge to a new situation; the answer is typically implied by the information in the passage. These questions often start “if.… then.…” (for example, “if we modify the experiment in the passage like this, then what result would we expect?”). Implicit style questions make up about 40 percent of the total number of questions.

In the CARS section, the questions fall into four main categories:

1)   Specific questions: These questions either ask you for facts from the passage (Retrieval questions) or require you to deduce what is most likely to be true based on the passage (Inference questions).

2)   General questions: These questions ask you to summarize themes (Main Idea and Primary Purpose questions) or evaluate an author’s opinion (tone/attitude questions).

3)   Reasoning questions: These questions ask you to describe the purpose of, or support provided for, a statement made in the passage (Structure questions) or to judge how well the author supports his or her argument (Evaluate questions).

4)   Application questions: These questions ask you to apply new information from either the question stem itself (New Information questions) or from the answer choices (Strengthen, Weaken, and Analogy questions) to the passage.

More detail on question types and strategies can be found in Chapter 2.


Before Test Day

•   Take a trip to the test center a day or two before your actual test date so that you can easily find the building and room on test day. This will also allow you to gauge traffic and see if you need money for parking or anything like that. Knowing this type of information ahead of time will greatly reduce your stress on the day of your test.

•   Don’t do any heavy studying the day before the test. Try to get a good amount of sleep during the nights leading up to the test.

•   Eat well. Try to avoid excessive caffeine and sugar. Ideally, in the weeks leading up to the actual test you should experiment a little bit with foods and practice tests to see which foods give you the most endurance. Aim for steady blood sugar levels during the test: sports drinks, peanut-butter crackers, trail mix, etc. make good snacks for your breaks and lunch.

General Test Day Info and Tips

•   On the day of the test, you’ll want to arrive at the test center at least a half hour prior to the starting time of your test.

•   Examinees will be checked in to the center in the order in which they arrive.

•   You will be assigned a locker or secure area in which to put your personal items. Textbooks and study notes are not allowed, so there is no need to bring them with you to the test center.

•   Your ID will be checked, a digital image of your fingerprint will be taken, and you will be asked to sign in.

•   You will be given scratch paper and a couple of pencils, and the test center administrator will take you to the computer on which you will complete the test. (If a white-board and erasable marker is provided, you can specifically request scratch paper at the start of the test.) You may not choose a computer; you must use the computer assigned to you.

•   Nothing is allowed at the computer station except your photo ID, your locker key (if provided), and a factory sealed packet of ear plugs; not even your watch.

•   If you choose to leave the testing room at the breaks, you will have your fingerprint checked again, and you will have to sign in and out.

•   You are allowed to access the items in your locker, except for notes and cell phones. (Check your test center’s policy on cell phones ahead of time; some centers do not even allow them to be kept in your locker.)

•   Don’t forget to bring the snack foods and lunch you experimented with in your practice tests.

•   At the end of the test, the test administrator will collect your scratch paper and shred it.

•   Definitely take the breaks! Get up and walk around. It’s a good way to clear your head between sections and get the blood (and oxygen!) flowing to your brain.

•   Ask for new scratch paper at the breaks if you use it all up.