Simulado MCAT

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Todas as 15 questões de uma vez

Prefere ler antes de jogar? Todas as questões da amostra estão listadas abaixo. As respostas e as explicações ficam fechadas até você abrir.

1. 1. A person meets the same pathogen for the second time and clears it far faster than the first time. Which feature of the immune system best explains the difference?

   • A. Neutrophils now reach the site of infection sooner than they did before
   • B. The complement system was permanently strengthened by the first exposure
   • C. Memory B and T cells left by the first exposure mount a faster and larger specific response
   • D. Physical barriers such as skin and mucus have adapted to that particular pathogen
   Mostrar resposta e explicação

   Resposta: C. Memory B and T cells left by the first exposure mount a faster and larger specific response

   Innate defenses, meaning barriers, phagocytes and complement, respond the same way every time and keep no record of what they met. The adaptive arm does keep a record, because clonal selection during the first exposure leaves behind long lived memory B and T cells specific to that antigen. On re-exposure those cells expand quickly, so antibody appears sooner and climbs higher, which is the secondary response. That is the effect vaccines are built to produce without the first illness.

2. 2. What is the net yield of glycolysis per molecule of glucose in the cytosol?

   • A. 2 ATP, 2 NADH and 2 pyruvate
   • B. 4 ATP, 2 NADH and 2 pyruvate
   • C. 2 ATP, 2 FADH2 and 2 lactate
   • D. 36 ATP, 2 NADH and 2 pyruvate
   Mostrar resposta e explicação

   Resposta: A. 2 ATP, 2 NADH and 2 pyruvate

   Substrate level phosphorylation makes four ATP in the payoff phase, but two are spent priming the sugar in the investment phase, so the net is two. Glycolysis also reduces two NAD+ to NADH and ends at two pyruvate. None of it needs oxygen, which is why a cell can run glycolysis when the electron transport chain is stalled, as long as it can regenerate NAD+ some other way.

3. 3. Which of the following are true of the tertiary structure of a globular protein?

   Marque todas as opções corretas.

   • A. Hydrophobic side chains tend to cluster in the interior, away from water
   • B. It is determined mainly by hydrogen bonding between backbone amide and carbonyl groups
   • C. Disulfide bridges can form between cysteine residues that are far apart in the sequence
   • D. It refers to the association of two or more separate polypeptide chains
   • E. Salt bridges between oppositely charged side chains help hold the fold together
   Mostrar resposta e explicação

   Resposta: A. Hydrophobic side chains tend to cluster in the interior, away from water, C. Disulfide bridges can form between cysteine residues that are far apart in the sequence, E. Salt bridges between oppositely charged side chains help hold the fold together

   Tertiary structure is the three dimensional fold of one chain, and it is driven by side chain interactions: the hydrophobic effect burying nonpolar residues, disulfide bonds between cysteines, salt bridges, and hydrogen bonds between side chains. Backbone hydrogen bonding is what defines secondary structure, the helices and sheets. Two or more chains coming together is quaternary structure.

4. 4. Complete the sentence.

   In oxidative phosphorylation, electrons passed down the chain are finally handed to _____, and the proton gradient across the inner mitochondrial membrane drives _____.

   Opções para a lacuna 1: carbon dioxide, oxygen, NAD+, pyruvate

   Opções para a lacuna 2: ATP synthase, the citric acid cycle, glycolysis

   Mostrar resposta e explicação

   Resposta: oxygen, ATP synthase

   Oxygen is the terminal electron acceptor and combines with protons to form water, which is why the whole chain backs up without it. The energy released as electrons fall is used to pump protons out, storing energy as an electrochemical gradient. ATP synthase then lets protons flow back down that gradient and uses the flow to phosphorylate ADP, a coupling known as chemiosmosis.

5. 5. In E. coli, glucose is plentiful and lactose is absent. What is the lac operon doing?

   • A. The repressor is inactive, so transcription runs at a high rate
   • B. cAMP is high, so CAP binds and strongly activates transcription
   • C. Lactose binds the repressor and pulls it off the operator
   • D. The repressor sits on the operator and transcription is largely off
   Mostrar resposta e explicação

   Resposta: D. The repressor sits on the operator and transcription is largely off

   The lac operon is under negative control by the repressor and positive control by CAP. With no lactose there is no inducer to lift the repressor, so it stays bound to the operator. Plentiful glucose also keeps cAMP low, so CAP does not bind and gives no boost. Both signals point the same way: do not build enzymes for a sugar that is not there.

6. 6. Two aqueous solutions sit either side of a membrane that lets water through but no solute. Solution A is 0.10 molar glucose and solution B is 0.10 molar sodium chloride. What happens?

   • A. Water moves toward the glucose, because glucose is the larger molecule
   • B. Water moves toward the sodium chloride, because it splits into about twice as many particles
   • C. There is no net movement, because the two molarities are equal
   • D. Water moves toward the glucose, because ionic compounds cannot generate osmotic pressure
   Mostrar resposta e explicação

   Resposta: B. Water moves toward the sodium chloride, because it splits into about twice as many particles

   Osmotic pressure is a colligative property, so it counts dissolved particles and ignores what those particles are. Sodium chloride dissociates into two ions per formula unit, which puts 0.10 molar NaCl near 0.20 osmolar while the glucose stays at 0.10. Water moves toward the side that is more concentrated in particle terms, so it moves toward the salt. The same counting explains freezing point depression and boiling point elevation.

7. 7. Two identical 10 ohm resistors are connected in parallel across a battery. What is the resistance of the pair, and how does it compare with one resistor on its own?

   • A. 20 ohms, which is larger than either resistor alone
   • B. 10 ohms, the same as either resistor alone
   • C. 5 ohms, which is smaller than either resistor alone
   • D. 0 ohms, because parallel paths cancel each other
   Mostrar resposta e explicação

   Resposta: C. 5 ohms, which is smaller than either resistor alone

   Parallel resistors add as reciprocals, so one over the total equals one tenth plus one tenth, and the total is 5 ohms. Adding a parallel path always lowers total resistance, because current gains another route to take. Series resistors do the opposite and simply add. The same reasoning is why opening more parallel vascular beds lowers total peripheral resistance.

8. 8. Which statements about a galvanic cell, also called a voltaic cell, are correct?

   Marque todas as opções corretas.

   • A. The standard free energy change of the cell reaction is positive
   • B. Oxidation happens at the anode and reduction happens at the cathode
   • C. An external power supply is needed to drive the reaction forward
   • D. The standard cell potential is positive
   • E. The salt bridge keeps each half cell electrically neutral as the reaction runs
   Mostrar resposta e explicação

   Resposta: B. Oxidation happens at the anode and reduction happens at the cathode, D. The standard cell potential is positive, E. The salt bridge keeps each half cell electrically neutral as the reaction runs

   A galvanic cell runs a redox reaction that is already favorable, so its standard cell potential is positive and its standard free energy change is negative, the two tied together by delta G naught equals minus n F E naught. Oxidation at the anode and reduction at the cathode holds in every electrochemical cell, so that pairing is not what separates the two types. Direction is what separates them, since an electrolytic cell needs an outside supply to push an unfavorable reaction uphill. The salt bridge moves ions between the half cells to cancel the charge buildup that would otherwise halt the reaction within seconds.

9. 9. Complete the sentence.

   A reaction whose enthalpy change is negative and whose entropy change is positive is _____.

   Opções para a lacuna 1: never spontaneous, spontaneous only at high temperature, spontaneous at every temperature, spontaneous only at low temperature

   Mostrar resposta e explicação

   Resposta: spontaneous at every temperature

   Gibbs free energy change equals enthalpy change minus temperature times entropy change. A negative enthalpy term and a positive entropy term both push that value negative, and absolute temperature is always positive, so the sign never flips. Spontaneous says nothing about speed, though. A reaction can be thermodynamically favorable and still sit untouched for years behind a large activation barrier.

10. 10. Students are told a hard test measures ability in an area where their group is stereotyped as weaker. They score lower than an otherwise identical group told the same test is a problem-solving exercise. This result is usually explained as:

    • A. social loafing
    • B. the bystander effect
    • C. deindividuation
    • D. stereotype threat
    Mostrar resposta e explicação

    Resposta: D. stereotype threat

    Stereotype threat is the drop in performance that appears when someone is reminded of a negative stereotype about a group they belong to, because the resulting worry and self-monitoring consume the working memory the task needs. Nothing about ability changed between the two groups here, only the framing of the task, which is why the instructions alone moved the scores. Social loafing, the bystander effect and deindividuation are all effects of being in a group, and none of them turn on how a task is described to an individual.

11. 11. Which of the following are true of classical conditioning?

    Marque todas as opções corretas.

    • A. A previously neutral stimulus comes to produce a response on its own
    • B. The response is voluntary and is shaped by the consequences that follow it
    • C. Presenting the conditioned stimulus repeatedly without the unconditioned stimulus leads to extinction
    • D. After extinction, the conditioned response can reappear later with no new training
    • E. Learning requires the learner to watch a model being rewarded
    Mostrar resposta e explicação

    Resposta: A. A previously neutral stimulus comes to produce a response on its own, C. Presenting the conditioned stimulus repeatedly without the unconditioned stimulus leads to extinction, D. After extinction, the conditioned response can reappear later with no new training

    Classical conditioning pairs a neutral stimulus with one that already produces a reflexive response until the neutral stimulus produces it alone. Break the pairing and the response fades, which is extinction, and it can come back on its own later, which is spontaneous recovery. Behavior shaped by its consequences is operant conditioning, and learning by watching a model is observational learning.

12. 12. Complete the sentence.

    The system that holds a few items for a matter of seconds while you actively work on them is _____. Recalling a fact more easily in the room where you first learned it is an example of _____.

    Opções para a lacuna 1: working memory, sensory memory, procedural memory

    Opções para a lacuna 2: proactive interference, the serial position effect, context dependent retrieval

    Mostrar resposta e explicação

    Resposta: working memory, context dependent retrieval

    Sensory memory holds a raw impression for well under a second, working memory holds a small handful of items while you manipulate them, and long term memory has no known practical ceiling. Retrieval is a separate problem from storage, since a memory can be stored perfectly well and still be hard to reach without the right cue. Context dependent retrieval is one of those cues, where the surroundings present at encoding are reinstated at recall, and state dependent retrieval does the same with internal state.

13. 13. Read the excerpt, then answer the question. The catalogue is the quiet argument of a museum. Curators speak of hanging a room, of letting one canvas answer another, and visitors read the sequence as though it were natural. It is not. Every wall states a claim about what belongs beside what, and about which century explains which. A visitor who walks the rooms in order absorbs a thesis she was never asked to accept, and rarely notices that a thesis was offered at all. Which of the following best states the main idea of the passage?

    • A. Museums ought to display their collections in strict chronological order
    • B. The arrangement of a museum makes an argument that most visitors take as given
    • C. Curators disagree sharply with one another about which paintings matter most
    • D. Visitors would learn more from reading a catalogue than from walking the galleries
    Mostrar resposta e explicação

    Resposta: B. The arrangement of a museum makes an argument that most visitors take as given

    The passage says every wall states a claim and that visitors absorb the resulting thesis without noticing it, which is the one idea that covers the whole excerpt. Main idea questions reward the choice that spans the passage, not a detail lifted from one line. The option about chronological order and the one about catalogues both recommend something the author never recommends, and the option about curators disagreeing introduces a conflict the passage never mentions.

14. 14. Read the excerpt, then answer the question. Economists once treated household labor as a residual, a thing done in the hours left over after real work. The convention was convenient. Unpaid hours resisted measurement, and what resists measurement tends to fall out of the model. When time use surveys finally arrived, they did not so much discover housework as make it countable, and the finding was greeted less as news than as an accounting problem. The hours had always been there. Only the ledger had changed. The author's remark that the surveys did not so much discover housework as make it countable most nearly implies that:

    • A. the work in question was new to the period the surveys covered
    • B. economists had deliberately concealed the existence of unpaid labor
    • C. the surveys changed what could be measured rather than what was happening
    • D. time use surveys were less accurate than the methods that came before them
    Mostrar resposta e explicação

    Resposta: C. the surveys changed what could be measured rather than what was happening

    The last two sentences say the hours had always been there and only the ledger changed, so the shift was in measurement and not in behavior. Reasoning questions want the smallest step past what the text supports. Deliberate concealment is far stronger than anything the author claims, since he calls the old convention convenient rather than dishonest, and the passage never compares the accuracy of one method with another.

15. 15. Read the excerpt, then answer the question. Defenders of the classics rarely argue that old books are useful. They argue instead that usefulness is the wrong test, and that a culture which asks only what a thing is for will end by keeping nothing it cannot spend. The claim has force, and it also has a convenient shape, since any objection can be dismissed as proof of the very narrowness complained of. An argument that cannot lose is not thereby strong. It has only stopped being an argument. Which best describes the author's attitude toward the defense he describes?

    • A. Sympathetic but critical, since he grants the defense force and then objects to its shape
    • B. Full agreement, since he says outright that the claim has force
    • C. Dismissive, since he holds that old books have no practical use
    • D. Neutral, since he only reports what defenders of the classics say
    Mostrar resposta e explicação

    Resposta: A. Sympathetic but critical, since he grants the defense force and then objects to its shape

    The author concedes that the claim has force, which rules out dismissal, and then complains that a defense treating every objection as evidence for itself has stopped being an argument. That is criticism of the reasoning, not of old books, so he never takes the dismissive position either. Attitude questions on this section usually land on a mixed answer whenever a passage contains both a concession and a complaint.

O que é o MCAT e como ele é pontuado

O MCAT é escrito e aplicado pela Association of American Medical Colleges. Ele tem quatro seções pontuadas: Chemical and Physical Foundations of Biological Systems, Critical Analysis and Reasoning Skills, Biological and Biochemical Foundations of Living Systems e Psychological, Social, and Biological Foundations of Behavior. Cada seção é pontuada numa escala de 118 a 132, então o total vai de 472 a 528, e 500 fica no ponto médio dessa faixa. Não existe nota de corte. A AAMC publica os percentis de cada pontuação, e cada faculdade de medicina decide por conta própria o que quer ver, então o único parâmetro útil é o perfil de notas das faculdades para as quais você pretende se candidatar.

A StudyPDF não tem vínculo com a AAMC, e nada nesta página é um produto oficial da AAMC. Cada questão e cada explicação aqui foi escrita pela equipe da StudyPDF a partir das categorias de conteúdo que a AAMC publica, e os trechos de leitura das três últimas questões também foram escritos por nós. Nenhum item da AAMC, nem de qualquer outra banca, foi reproduzido em nenhum ponto desta página. Isso corta para os dois lados. Como as questões são nossas, elas só conseguem se aproximar da prova real, então use-as para achar lacunas e use o material oficial de prática da AAMC quando quiser uma leitura confiável de onde sua pontuação realmente está.

O formato é longo. Cada uma das três seções de ciências dá 59 questões em 95 minutos, e a seção de raciocínio dá 53 questões em 90 minutos, o que coloca o tempo total sentado em cerca de sete horas e meia, contando os intervalos e o check-in. A maioria das questões vem presa a um texto, com um conjunto menor de questões discretas independentes, só nas seções de ciências. Nada é descontado por resposta errada, então deixar em branco é sempre pior do que chutar. As regras do dia da prova, a estrutura dos intervalos, o agendamento e a ajuda com as taxas mudam, então confirme os detalhes atuais em students-residents.aamc.org em vez de confiar num número que você leu num fórum.

Como usar esta amostra

As 15 questões abaixo seguem em miniatura o próprio equilíbrio da prova. Cinco vêm dos fundamentos biológicos e bioquímicos, quatro dos fundamentos químicos e físicos, três dos fundamentos psicológicos e sociais do comportamento, e três são itens de análise crítica e raciocínio. Cada item de raciocínio traz seu próprio trecho curto, escrito por nós no registro que essa seção usa, para você treinar a habilidade sem precisar caçar um texto antes. A prova real usa só múltipla escolha de resposta única, então os itens de marcar todas as corretas e de completar a lacuna aqui são um recurso de estudo, não uma prévia do formato. Eles estão na mistura porque se comprometer com cada parte de uma resposta expõe lacunas que quatro alternativas bem arrumadas conseguem esconder. Nenhuma destas é uma questão real da prova, e nenhuma delas é orientação médica. Isto é prática para a prova, nada além disso.

Faça tudo de uma vez, sem consultar anotações, e depois leia a explicação de cada questão, inclusive das que você acertou. No MCAT um chute com sorte e uma resposta pensada ficam idênticos no boletim e completamente diferentes na sua cabeça, então a revisão é onde o aprendizado acontece. Trate um erro como um tema, não como um fato. Se você derrubou a questão de pressão osmótica e a de termodinâmica, o problema provavelmente é que você está decorando equações em vez de ler o que cada variável de fato representa.

Depois disto, divida seu tempo de estudo com honestidade. A revisão de conteúdo fecha lacunas, mas o avanço na pontuação costuma vir de simulados completos cronometrados e de revisá-los com calma. A seção de raciocínio é a exceção, porque ela recompensa mais a leitura diária constante de prosa argumentativa densa do que qualquer lista de conteúdo. O tempo é uma habilidade em si. Noventa e cinco minutos para 59 questões deixam pouco mais de um minuto e meio para cada uma, e a maioria das pessoas perde pontos no fim de uma seção, não no começo, então, quando o conteúdo estiver firme, treine contra o relógio em vez de sem cronômetro. Os dois quizzes irmãos linkados abaixo aprofundam as seções de ciências e o raciocínio, então faça os três e veja qual dói.

Como a StudyPDF cria simulados completos do seu próprio material

Quinze questões conseguem mostrar onde você está inseguro. Elas não deixam você pronto sozinhas, e um banco genérico raramente combina com a ênfase do livro de revisão, do curso ou das anotações de aula com que você está de fato trabalhando.

A StudyPDF trabalha a partir do seu material. Você envia seus livros de revisão do MCAT, seus slides de bioquímica ou de psicologia, ou os resumos de capítulo que você mesmo escreveu, e o Bo, o agente de estudo, cria simulados completos a partir dessas páginas exatas. Cada questão é baseada no seu material, e cada explicação cita de onde veio a resposta, então, quando algo parecer errado, dá para ir direto à fonte e conferir. Você pode gerar simulados novos quantas vezes quiser, restringir a uma área só, como aminoácidos, circuitos ou métodos de pesquisa, e acompanhar quais conceitos continuam voltando errados.

Você não precisa enviar nada para começar. Se não tiver nenhum arquivo à mão, é só dizer um tema, por exemplo química de ácidos e bases, fisiologia muscular ou estratificação social, e o Bo escreve um simulado a partir disso. Começar é grátis.