The Hardest Sample MCAT Questions and How to Answer Them

The MCAT is a beast, plain and simple. It’s long, grueling, and filled with tricky questions that seem to taunt you with their complexity. But here’s the thing: you don’t need to be a walking encyclopedia of every piece of science knowledge to ace this test. What you do need is a strategy, a way to break down tough questions, and the confidence to trust your instincts. In this post, I’m going to walk you through some of the hardest types of MCAT questions, highlight common mistakes test-takers make, and give you actionable advice on how to approach them.

One key thing to remember as you prepare for the MCAT is that process of elimination (POE) is your friend. You do not need to be an expert on every single answer choice. In fact, you shouldn’t be. Most questions on the MCAT are designed to test your ability to think critically and apply your knowledge to scenarios, not necessarily to test your ability to memorize every fact. The good news? You can often eliminate a couple of answer choices right off the bat, making your job that much easier.

Let’s dive into some of the most challenging MCAT question types, explore how to approach them with this strategy in mind, and review sample questions for each type to help you practice effectively

1. Biology & Biochemistry: Mechanisms of Enzyme Action

Sample Question:

An enzyme catalyzes the conversion of substrate A to product B. The enzyme binds to A, and the reaction is greatly accelerated compared to the rate at which A spontaneously undergoes the same conversion. The enzyme’s active site contains an amino acid with a specific side chain that forms a covalent bond with A during the reaction. Which of the following best describes this enzyme’s mechanism of action?

• A) The enzyme is acting as a catalyst in an irreversible reaction.
• B) The enzyme stabilizes the transition state, lowering the activation energy.
• C) The enzyme increases the activation energy of the reaction.
• D) The enzyme functions through a mechanism of feedback inhibition.

Common Pitfall:

Many test-takers get tripped up by the wording in questions like this. Specifically, the presence of covalent bonds or the mention of enzymes can lead you to overthink the details. In this case, A sounds tempting because of the mention of a covalent bond, but it’s a misdirection. The real focus should be on the enzyme’s mechanism of action, which is ultimately about lowering the activation energy.

The Right Approach:

Here’s where POE comes into play. Start by ruling out A. The question doesn’t say the reaction is irreversible, just that it’s catalyzed, so we can eliminate that choice right away. C can also be discarded because an enzyme’s role is to lower activation energy, not increase it. D doesn’t fit because feedback inhibition involves regulation, not catalysis. That leaves you with B, which correctly describes the enzyme’s function of stabilizing the transition state.

2. Physics: Forces and Motion

Sample Question:

A 10 kg block is sliding down an inclined plane with an angle of 30°. The coefficient of kinetic friction between the block and the surface is 0.2. What is the acceleration of the block down the plane?

• A) 4.9 m/s²
• B) 2.0 m/s²
• C) 7.5 m/s²
• D) 3.0 m/s²

Common Pitfall:

This question isn’t as much about knowing the exact formula as it is about avoiding calculation errors and misinterpreting the force components. A common mistake is neglecting the frictional force or miscalculating the net force parallel to the incline.

The Right Approach:

First, break the forces into components: gravity pulls the block down, but friction resists that motion. The force parallel to the incline is F∥=mgsin⁡θF_{\parallel} = mg \sin \thetaF∥​=mgsinθ, and the frictional force is Ffriction=μmgcos⁡θF_{\text{friction}} = \mu mg \cos \thetaFfriction​=μmgcosθ. The net force is the difference between the parallel component and the frictional force. From there, use Newton’s second law, F=maF = maF=ma, to solve for acceleration. When you do the math, you’ll find that the acceleration is B) 2.0 m/s². POE here helps, as you can rule out the extremes (A and C) based on the expected range for such a problem.

3. Psychology/Sociology: Social Theories and Behavior

Sample Question:

According to social learning theory, which of the following best describes the process through which an individual learns to act aggressively?

• A) The individual is taught to act aggressively through punishment.
• B) The individual observes and imitates aggressive behavior from others.
• C) The individual is conditioned to respond aggressively in certain situations.
• D) The individual’s aggression is a direct result of repressed emotions.

Common Pitfall:

Test-takers often mix up social learning theory with other psychological theories. A common mistake here is confusing observational learning (which is the core of social learning theory) with classical or operant conditioning. Mix-ups like this are common when approaching the hardest MCAT questions.

The Right Approach:

Start by eliminating A and C because neither punishment nor conditioning is central to social learning theory. D may seem tempting if you’re familiar with Freudian theory, but it doesn’t apply here. That leaves you with B, which correctly identifies that aggression can be learned through observing and imitating others. Even if you’re not 100% sure, B aligns with the most well-established aspects of social learning theory.

4. Chemistry: Equilibrium and Le Chatelier’s Principle

Sample Question:

If a system at equilibrium is subjected to an increase in temperature, which of the following is most likely to occur?

• A) The concentration of products increases.
• B) The concentration of reactants increases.
• C) The reaction shifts to the right.
• D) The reaction shifts to the left.

Common Pitfall:

Many test-takers confuse the direction of the shift in equilibrium when temperature changes, especially in exothermic and endothermic reactions. A common mistake is not recognizing whether the reaction is endothermic or exothermic.

The Right Approach:

The key to solving this is understanding that Le Chatelier’s Principle tells us that if a system at equilibrium is disturbed, the system will shift to counteract that disturbance. If the temperature increases, the system will shift in the direction that absorbs heat (endothermic direction). For exothermic reactions, this means the equilibrium shifts left, while for endothermic reactions, the equilibrium shifts right. Use your knowledge of the reaction’s heat properties to make the right call. In this case, D is the correct answer if the reaction is exothermic.

5. Critical Analysis and Reasoning Skills (CARS)

Sample Question:

The passage describes the ethical dilemma of using animals in scientific experiments. The author argues that while animal testing has contributed to medical advancements, it raises concerns about the moral treatment of animals. The most likely conclusion the author would support is:

• A) Animal testing should be banned entirely in all circumstances.
• B) The benefits of animal testing outweigh the moral concerns.
• C) The ethical concerns regarding animal testing should be addressed without eliminating it entirely.
• D) Animal testing has not contributed significantly to medical advancements.

Common Pitfall:

The CARS section trips up a lot of people because it doesn’t require any specific content knowledge but instead relies on reading comprehension and critical reasoning. The biggest mistake here is trying to answer the question based on personal opinion or jumping to conclusions based on emotion rather than the text.

The Right Approach:

In CARS, focus on the tone and argument of the passage. The author acknowledges the moral concerns but doesn’t outright call for a ban on animal testing. This suggests that the conclusion would likely be C) The ethical concerns regarding animal testing should be addressed without eliminating it entirely, as it aligns with the author’s nuanced argument.

General Tips for Tackling The Hardest MCAT Questions

Focus on the Question, Not the Details

MCAT questions can sometimes include a lot of extraneous information, and test-makers love to throw in scientific jargon. Read the question carefully, but don’t get bogged down by every single detail. Pay attention to the main concepts and relationships, and trust yourself to recognize what’s important.

Use POE (Process of Elimination)

As we’ve seen, you don’t need to be an expert on every concept. More often than not, you can eliminate one or two answer choices immediately because they are obviously wrong. Use that to your advantage, and you’ll have a better shot at making an educated guess when necessary.

Don’t Overthink the Hardest MCAT Questions

Sometimes, a tricky question is designed to make you second-guess yourself. Stick to your first instinct unless you’re absolutely sure the answer is wrong. Overthinking can lead to mistakes and time wasted.

Time Management is Key

The MCAT is a time-intensive test. Don’t linger on tough questions for too long. If you’re stuck, make your best guess, mark the question, and come back to it if time allows.

Know Your Weak Areas

The MCAT covers a lot of material, and it’s okay if you’re not an expert in every area. Focus your study on your weakest areas, but don’t neglect your strengths. A balanced approach will give you the best shot at success.

By understanding the common pitfalls, embracing the process of elimination, and approaching each question with a clear strategy, you’ll set yourself up for success. You don’t need to be perfect, but you do need to be methodical. Keep practicing, stay confident, and trust that you have the knowledge and tools to tackle even the toughest MCAT questions.

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