MCAT Biology Practice Questions and Answers

Before You Start: Tips from our MD Experts

The first key to studying the many subjects covered on the MCAT biology section is thorough content review. Since there are many complex topics to learn, you’ll need to use active learning techniques and keep your studying engaging and interesting.

“I made a conscious effort to relate biology and chemistry concepts to real-life applications and examples. This not only enhanced my understanding but also kept me motivated to learn. I also incorporated variety into my study sessions by alternating between learning materials and practicing questions … One strategy that helped me study for these sections was breaking down the content into smaller, manageable chunks and studying consistently over time rather than cramming. I also made use of active learning techniques such as teaching the material to myself and creating concept maps to organize information.” – Dr. Cathleen Kuo, MD.

“Reading each paragraph and summarizing it in my own words and writing down key findings inequation form (i.e., noting correlation between variables) … Watching YouTube videos and doing flashcards was a great way to learn the content and review the study material on days that I was not doing passage-based questions. This made studying fun and productive while ensuring my well-being.” – Dr. Neel Mistry, MD, University of Ottawa Faculty of Medicine.

The second key to acing MCAT biology is using practice passages-based questions and reviewing the answers. So let’s dive into a few examples!

MCAT Biology Practice Passage, Questions and Answers #1

In the human body, immunity can be acquired in either an active or passive fashion. An example of immunity being acquired actively would be when a microorganism (an antigen) enters the human body and begins to spread throughout the body. The body responds to this threat by producing antibodies as well as activating lymphocyte populations which work together to eliminate the threat. Memory lymphocytes are produced by this exposure that will re-engage with the antigen should the microorganism attack again in the future.

In contrast, an example of immunity being acquired passively would be when an individual receives pre-formed antibodies from another individual. An example of this would be IgG antibodies that are transferred from a mother to a fetus via the placenta. Additionally, IgA and IgG antibodies are often transferred from a mother to child when the child is breast fed.

Immunity can be acquired either naturally or artificially. An example of immunity being acquired naturally would be if an individual were to become sick with measles. The body will produce antibodies against this disease allowing for the individual to have acquired their immunity naturally. Alternatively, individuals can acquire immunity from measles artificially by undergoing vaccination. The body will produce antibodies in response to the vaccination, allowing the individual to have artificially acquired active immunity against this disease. Vaccinations allow for the acquisition of artificially acquired active immunity as they contain microorganisms (antigen) that are considered dead or attenuated (weakened) which allow for the body to create a memory response that can be engaged should the individual be infected later in their lifetime.

MCAT Biology Practice Questions and Answers #1

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MCAT Biology Practice Passage, Questions and Answers #2

Approximately 20% of the human body is comprised of protein of animal origin and because of this our bodies require multiple safety mechanisms to avoid the digestion of our own tissue. One of these well-known safety mechanisms are mucopolysaccharides (a core component of mucus) which line the epithelial tissue of the digestive tract. Mucus cannot be digested which allows for it to protect the tissues from digestive acids and enzymes. Additionally, the pancreas houses proteolytic enzymes in their inactive form (zymogens) which spares the pancreatic cells from being digested.

One safety mechanism that can be found in the GI tract is the rapid turnover of cells. Specifically, the endothelial lining of the GI tract is replaced every 5-7 days which allows for the maintenance of a protective barrier between the digestive acids and enzymes of the GI tract and the rest of the body’s tissues.

A final safety mechanism that can be found in the digestive tract is bicarbonate that is released by the pancreas. While the stomach is primarily responsible for acidifying a bolus of food so that it can be broken down, the pancreas will release bicarbonate after this breakdown in order to neutralize the pH of the duodenum.

MCAT Biology Practice Questions and Answers #2

Want to learn how to ace the MCAT with a 528 score? Check out our video:

MCAT Biology Practice Passage, Questions and Answers #3

Circulatory shock is essentially when there is not enough blood flowing through the circulatory system to meet the oxygen demands of the body’s tissues. If this shock is not remedied quickly it can lead to the death of the patient.

One type of circulatory shock is hypovolemic shock which occurs when the body’s blood volume is too low. This low amount of blood volume results in a decrease of the patient’s blood pressure and an overall decrease in the patient’s cardiac output. The body’s arterial blood pressure is proportional to blood flow, therefore, if the patient is in hypovolemic shock there will be an inadequate amount of blood flow to the body’s organs and tissues.

In the human body, baroreceptors can sense a drop in a person’s blood pressure. When baroreceptors sense this drop, these receptors will stimulate the sympathetic nervous system which will help correct the patient’s low blood pressure in hypovolemic shock. Specifically, the sympathetic nervous system will enable a cascade of events to occur which will cause vasoconstriction of the arterioles allowing for an increase in the patient’s blood pressure.

To calculate a patient’s blood pressure, one can use the equation below:

BP = CO X TPR

Blood pressure (BP) is related to the patient’s cardiac output (CO) and total peripheral resistance (TPR). It is important to note that resistance to blood flow is inversely proportional to the radius of the blood vessel raised to the fourth power. Cardia output is equivalent to the heart rate times the stroke volume of the ventricles of the heart.

MCAT Biology Practice Questions and Answers #3

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