If you’re preparing for the Medical College Admission Test (MCAT), you are going to want to consult the experts. These selections from Kaplan’s MCAT Question of the Day series can help you sharpen your skills as you prepare to begin your potential journey into medical training.
The questions below come from three of the four MCAT sections—biological and biochemical foundations of living systems; chemical and physical foundations of biological systems; and psychological, social, and biological foundations of behavior. A fourth section, critical analysis and reasoning skills (commonly referred to as CARS), is based largely on inference. Medicine can be a career that is both challenging and highly rewarding but figuring out a medical school’s prerequisites and navigating the application process can be a challenge unto itself. For students preparing for the medical school, the AMA premed glossary guide has the answers to frequently asked questions, For those already in medical school, the AMA and Kaplan have teamed up to support you in reaching your goal of passing the USMLE® or COMLEX-USA®. If you're looking for additional resources, Kaplan provides free access to tools for pre-clinical studies, including Kaplan’s Lecture Notes series, Integrated Vignettes, Shelf Prep and more.
Section: Biological and biochemical foundations of living systems
Question: The formation of α-d-glucopyranose from β-d-glucopyranose is called:
A. Mlycosidation.
B. Mutarotation.
C. Enantiomerization.
D. Racemization.
The correct answer is B.
Kaplan explains why: Mutarotation is the interconversion between anomers of a compound. Enantiomerization and racemization, choices (C) and (D), mean the same thing as each other: the formation of a mirror image or optically inverted form of a compound. Glycosidation, choice (A), is the addition of a sugar to another compound.
Section: Chemical and physical foundations of biological systems
Question: For the most part, biological pH is slightly basic. However, the stomach is very acidic, and its contents must be swiftly neutralized by basic bicarbonate ions upon entering the small intestine, which has a basic pH. How many liters of 2 M Ba(OH)2 are needed to titrate a 4 L solution of 6 M H3PO4?
A. 1.33 L
B. 12 L
C. 18 L
D. 56 L
The correct answer is C.
Kaplan explains why: Use the equivalence point equation:
NaVa = NbVb
Ba(OH)2 can dissociate to give two hydroxide ions, so its normality is 2 M × 2 = 4 N. H3PO4 can dissociate to give three hydronium ions, so its normality is 6 M × 3 = 18 N. Plugging into the equation, we get (18 N)(4 L) = (4 N)(Vb). Therefore, Vb is 18 L.
Section: Psychological, social and biological foundations of behavior
Question: A 9-year-old girl is brought to the pediatrician. Her parents describe that any time she is startled, she appears to collapse and fall asleep. She also complains of waking up in the morning unable to move. Which sleep disorder should be suspected?
A. Insomnia
B. Sleep deprivation
C. Narcolepsy
D. Sleep apnea
The correct answer is C.
Kaplan explains why: The patient and her parents are describing cataplexy (a sudden loss of muscle tone and intrusion of REM sleep during waking hours, usually in response to a startling or emotional trigger) and sleep paralysis (an inability to move despite being awake, usually when waking up in the morning). These symptoms are highly suggestive of narcolepsy; in fact, some consider cataplexy to be pathognomonic for (absolutely indicative of) the disorder.
