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Question of the Day: MCAT Biology

Carbonic anhydrase is a very important enzyme that is utilized by the body. The enzyme catalyzes the following reaction:

A class of drugs that inhibits this enzyme is carbonic anhydrase inhibitors (eg. acetazolamide, brinzolamide, dorzolamide). These drugs are commonly prescribed in patients with glaucoma, hypertension, heart failure, high altitude sickness and for the treatment of basic drugs overdose.   

In patients with hypertension, carbonic anhydrase inhibitors will prevent the reabsorption of sodium chloride  in the proximal tubule of the kidney. When sodium is reabsorbed back into the blood, the molecule creates an electrical force. This electrical force then pulls water along with it into the blood. As more water enters the blood, the blood volume increase. By preventing the reabsorption of sodium, water reabsorption is reduced and the blood pressure decreases. 

When mountain climbing, the atmospheric pressure is lowered as the altitude increases. As a result of less oxygen into the lungs, ventilation increases. From the equation above, hyperventilation will result in more  being expired. Based on Le Chatelier’s principle, the reaction will shift to the left. Since there is more bicarbonate than protons in the body, the blood will become more basic (respiratory alkalosis). To prevent such life threatening result, one would take a carbonic anhydrase inhibitor to prevent the reaction from shifting to the left.  

Carbonic anhydrase inhibitors are useful in patients with a drug overdose that is acidic. The lumen of the collecting tubule is nonpolar. Due to the lumen's characteristic, molecules that are also nonpolar and uncharged are able to cross the membrane and re-enter the circulatory system. Since carbonic anhydrase inhibitors alkalize the urine, acidic molecules stay in a charged state.

How will excess intake of a carbonic anhydrase inhibitor affect the hemoglobin dissociation curve?

No change

Shifts to the left

Shifts to the right

Shifts up

Shifts down

Completely overhauled in 2015, the Medical College Admissions Test (MCAT) is a major hurdle that every aspiring medical student in the United States faces. The MCAT has garnered a reputation as a challenging exam, and for many students, the uncertainty of the new exam makes their test anxiety more acute. Whether you need MCAT tutoring in AtlantaMCAT tutoring in Houston, or MCAT tutoring in San Francisco, working one-on-one with an expert may be just the boost your studies need.

The new MCAT is broken into the roughly familiar categories examinees have faced before, with the addition of a new social science-themed test section. These sections are as follows:

- Biological and Biochemical Foundations of Living Systems

- Chemical and Physical Foundations of Biological Systems

- Psychological, Social, and Biological Foundations of Behavior

- Critical Analysis and Reasoning Skills

Most examinees probably feel most comfortable with the first of these sections. Despite this, it is important to allocate time and effort evenly during exam preparation.

The Association of American Medical Colleges has indicated that there will be three categories within the Biological and Biochemical Foundations of Living Systems section. These are, broadly, as follows:

- Structure and function of biomolecules

- Organization of molecular and cellular components of life

- Complex organization and emergent properties of whole organisms

These are certainly broad categories, but they highlight some important changes relative to years past. It is clear that doing well in undergraduate biology and organic chemistry is the best foundation for success on the MCAT. These topics line up with typical content in any undergraduate biology or organic chemistry sequence. It also provides students with an idea of where to focus their studies. Varsity Tutors offers resources like free MCAT Biology Practice Tests to help with your self-paced study, or you may want to consider an MCAT Biology tutor.

There are also some surprises in the information from AAMC. In fact, there is now a focus that examinees may not have seen in years past, with biochemistry and biomolecules now featuring prominently. Historically, undergraduate biochemistry was not even required as a prerequisite for medical schools. Even now, it may not be part of a typical pre-medical curriculum at your institution, and is an excellent example of why it is so important to take control of your own preparation. It is critical to do your own research!

For many students, wondering where to start poses a serious challenge. You may have done your research, gathered materials, and feel that you are ready to go. But the volume of information is overwhelming! Making matters worse, many faculty or premedical advisors may be unsure of what exactly to expect on the 2015 MCAT. For students facing the inaugural exam, the challenge of any MCAT is now compounded with uncertainty. As a result, adequate preparation is more important than ever, and should be a major focus for any premedical student entering the second half of their undergraduate careers. Arguably the best way to begin preparation is to work with materials geared toward the revised MCAT, which reflects the changes to the exam in 2015. An exam like the MCAT rewards students who review by challenging themselves, completing practice questions, and interacting with others to mature their ideas and ensure the mental agility needed for MCAT success. In addition to the MCAT Biology Question of the Day and MCAT Biology tutoring, you may also want to consider using some of our MCAT Biology flashcards.

Want to start preparing for your MCAT right now? Answer our MCAT Biology question of the day! Each day, we feature a multiple-choice MCAT Biology question that you can use to assess your skill. After you choose a response, the correct answer is revealed, as well as a full explanation detailing how the question can be solved. If you answer correctly, you can feel more confident in your ability to face MCAT content. If you miss the question, it presents the opportunity for you to identify exactly where you erred in your reasoning, helping you avoid making the same mistake twice. Either way, answering our MCAT Biology question of the day can only help you continue to strengthen your MCAT knowledge, so check back every day for a new MCAT Biology question, and try out our other free MCAT Biology resources for practice tests, diagnostic tests, and other tools to help you learn this challenging material.

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