Medical Tests Medical Tests Certifications MCAT-TEST Questions & Answers

• Question 421:

  Which stimulus is the main factor that influences circadian rhythms?

  A. pain

  B. temperature

  C. pressure

  D. light

  Correct Answer: D

  Circadian rhythms are the bodily changes which follow a 24-hour cycle in response to changes in light levels.

• Question 422:

  Which category of memory would explicit memory be classed as?

  A. short-term memory

  B. sensory memory

  C. long-term memory

  D. procedural memory

  Correct Answer: C

  Explicit memory is the conscious memory of information and experiences.

• Question 423:

  Which part of the brain controls speech?

  A. hypothalamus

  B. cerebellum

  C. occipital lobe

  D. Broca's Area

  Correct Answer: D

  Broca's Area is located in the frontal lobe of the left hemisphere and controls speech production.

• Question 424:

  Which part of the endocrine system secretes adrenaline?

  A. adrenal medulla

  B. parathyroid

  C. anterior pituitary

  D. adrenal cortex

  Correct Answer: A

  The adrenal medulla is found in the adrenal gland and its cells secrete adrenaline, noradrenaline, dopamine and enkephalin. The other options are part of the endocrine system, but do not release adrenaline.

• Question 425:

  Which disease is caused by protein misfolding, which causes plaque accumulation in the brain?

  A. Alzheimer's disease

  B. schizophrenia

  C. Parkinson's disease

  D. depression

  Correct Answer: A

  In Alzheimer's disease, misfolding of amyloid beta protein and tau protein causes deposits to form around neurons in the brain.

• Question 426:

  Deoxygenated blood is received by the heart and then pumped out toward the lungs. The now-oxygenated blood is received again by the heart and pumped out toward the rest of the body. Which sequence of heart chambers correctly follows the path of blood described in the passage?

  A. right atrium - left ventricle - left atrium - right ventricle

  B. left atrium - right ventricle - right atrium - left ventricle

  C. right atrium - left atrium - left ventricle - right ventricle

  D. right atrium - right ventricle - left atrium - left ventricle

  Correct Answer: D

  Deoxygenated blood is received by the right atrium via large veins called the venae cavae. It is then transferred to the right ventricle through the tricuspid valve and subsequently exits the heart through the semi lunar valve and is transferred to the pulmonary artery, where it is pumped toward the lungs for oxygenation. Oxygenated blood is received by the left atrium and transferred to the left ventricle through the mitral valve.

• Question 427:

  An enzyme catalyst is kept in a solution buffered to the pH that maximizes activity for those enzymes found in the blood. The enzyme catalyzes a reaction that produces an acid whose pKa is 4.5. In this buffer solution, the acid product will be:

  A. primarily deprotonated.

  B. primarily protonated.

  C. protonated and deprotonated in roughly equal amounts.

  D. not formed.

  Correct Answer: A

  The blood has a pH around 7.4, making it somewhat basic. If this enzyme is in a solution buffered to a point to maximize enzymes found in the blood, then the buffer solution will have a pH of 7.35 to 7.45. When an acid is in a solution whose pH is higher than its pKa, the acid is deprotonated, making choice (A) the correct answer.

  B: The acid would be protonated if the buffer solution had a pH that was below 4.5.

  C: The acid would have equal concentrations of the acid and conjugate base form if the buffer had a pH of around 4.5.

  D: There's no reason for us to assume the product wouldn't form.

• Question 428:

  Noncompetitive inhibition differs from uncompetitive inhibition in that a noncompetitive inhibitor binds to an allosteric site on the enzyme and prevents it from catalyzing a reaction, whereas uncompetitive inhibitors bind to the enzyme-substrate complex and prevent catalysis. Increasing the substrate concentration would have which of the following effects?

  A. Increasing impact of uncompetitive inhibitor and decreasing concentration of noncompetitive inhibitor

  B. Decreasing impact of uncompetitive inhibitor and increasing impact of noncompetitive inhibitor.

  C. Increasing impact of uncompetitive inhibitor

  D. No effect

  Correct Answer: C

  As substrate concentration increases, there will be more binding between the substrate and the enzyme. More enzyme-substrate complex in solution means more opportunity for an uncompetitive inhibitor to bind. Thus, as substrate concentration increases, the impact of an uncompetitive inhibitor would be expected to increase.

  A: The concentration of a noncompetitive inhibitor isn't changed by changing the substrate concentration. B, D: As discussed above, the impact of an uncompetitive inhibitor would be increased.

• Question 429:

  The bacterial cells and virus particle, both have:

  A. a cell membrane.

  B. nuclear material.

  C. a cell wall.

  D. a slime layer.

  Correct Answer: B

• Question 430:

  The percentage of arthropods in total animal kingdom is:

  A. 85%

  B. 45%

  C. 75%

  D. 60%

  Correct Answer: C