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MCAT EXAM AND PRACTICE EXAM NEWEST 2026/
2027 TEST BANK| MEDICAL COLLEGE ADMISSION
TEST AAMC EXAM PREP WITH COMPLETE 400 REAL
EXAM QUESTIONS AND CORRECT VERIFIED
ANSWERS/ ALREADY GRADED A+ (MOST RECENT!!)
➢ Chemical and Physical Foundations of Biological Systems (Quest 1-100)
A researcher studies an enzyme-catalyzed reaction at 37°C. In the
absence of inhibitor, Vmax is 120 μmol/min and Km is 4.0 mM. A
competitive inhibitor is added at a concentration that doubles the
apparent Km without changing Vmax. At a substrate concentration of
4.0 mM, what reaction velocity should be expected?
A. 40 μmol/min
B. 60 μmol/min
C. 80 μmol/min
D. 120 μmol/min - Correct Answer - A. 40 μmol/min
Competitive inhibition doubles Km to 8.0 mM while Vmax remains 120
μmol/min. Using \(v=V_{max}[S]/(K_m+[S])\): \(v=120(4)/(8+4)=40\)
μmol/min.
During an experiment, a 0.020 mol sample of an ideal gas occupies 500
mL at 300 K. The gas is compressed isothermally until its volume is 125
mL. What is the final pressure if the initial pressure is 1.00 atm?
A. 0.25 atm
B. 2.00 atm
C. 4.00 atm
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D. 8.00 atm - Correct Answer - C. 4.00 atm
Temperature and amount of gas remain constant, so Boyle's law applies:
\(P_1V_1=P_2V_2\). Thus \(P_2=(1.00)(500/125)=4.00\) atm.
A weak acid HA has a pKa of 4.8. A buffer initially contains equal
concentrations of HA and A⁻. If the pH is increased to 5.8 while total
buffer concentration remains constant, which change occurs?
A. [HA] becomes 10 times [A⁻]
B. [A⁻] becomes 10 times [HA]
C. [A⁻] becomes equal to [HA]
D. [HA] becomes 100 times [A⁻] - Correct Answer - B. [A⁻] becomes 10
times [HA]
Henderson-Hasselbalch gives \(pH=pK_a+\log([A^-]/[HA])\). Since pH
− pKa = 1, the ratio is \(10^1=10\).
A 2.0-kg cart moves at 3.0 m/s on a horizontal frictionless track and
collides with a stationary 1.0-kg cart. The carts lock together after
impact. What is their combined speed immediately afterward?
A. 1.0 m/s
B. 1.5 m/s
C. 2.0 m/s
D. 3.0 m/s - Correct Answer - C. 2.0 m/s
Momentum is conserved: \((2.0)(3.0)+(1.0)(0)=(3.0)v\). Therefore,
\(v=2.0\) m/s.
Researchers place erythrocytes in three solutions. Solution X causes
cells to swell and lyse, solution Y produces no measurable change, and
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solution Z causes cells to shrink. Which relationship between the
solutions is most consistent with these observations?
A. X is hypotonic, Y is isotonic, Z is hypertonic
B. X is hypertonic, Y is hypotonic, Z is isotonic
C. X is isotonic, Y is hypertonic, Z is hypotonic
D. X is hypotonic, Y is hypertonic, Z is isotonic - Correct Answer - A. X
is hypotonic, Y is isotonic, Z is hypertonic
Water enters cells in hypotonic solutions, causing swelling. Isotonic
solutions produce no net water movement, while hypertonic solutions
cause water to leave cells.
A positively charged particle enters a uniform electric field with velocity
perpendicular to the field lines. Which trajectory will the particle follow
if magnetic effects and gravity are negligible?
A. A straight path parallel to the field
B. A circular path within the field
C. A parabolic path
D. A helical path around the field lines - Correct Answer - C. A parabolic
path
The electric force is constant and parallel to the electric field, producing
constant acceleration. With the initial velocity perpendicular to that
acceleration, the resulting trajectory is parabolic.
A patient receives an intravenous solution containing 0.90% NaCl.
Assuming NaCl dissociates completely into two ions, which property
primarily determines the solution's osmotic pressure?
A. Its total concentration of dissolved particles
B. The molecular mass of sodium chloride alone
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C. The density of the solvent alone
D. The electrical charge of chloride alone - Correct Answer - A. Its total
concentration of dissolved particles
Osmotic pressure is a colligative property dependent on the number of
dissolved particles. Complete NaCl dissociation increases the number of
osmotically active particles.
A reaction has ΔH = +85 kJ/mol and ΔS = +0.20 kJ/(mol·K). At what
temperature does the reaction become thermodynamically favorable
under standard conditions?
A. 213 K
B. 300 K
C. 425 K
D. 625 K - Correct Answer - C. 425 K
At the transition point, ΔG = 0. Therefore, \(T=\Delta H/\Delta
S=85/0.20=425\) K. Above this temperature, ΔG becomes negative.
A 1.0-L solution contains 0.10 mol of a monoprotic weak acid and 0.10
mol of its conjugate base. Which addition would most strongly resist a
subsequent small addition of strong acid?
A. 0.10 mol of water
B. 0.10 mol of the conjugate base
C. 0.10 mol of the weak acid
D. 0.10 mol of a neutral salt unrelated to the buffer - Correct Answer -
B. 0.10 mol of the conjugate base
The conjugate base directly reacts with added H⁺ to form the weak acid.
Increasing the conjugate-base reservoir therefore increases resistance to
added strong acid.
pg. 4
MCAT EXAM AND PRACTICE EXAM NEWEST 2026/
2027 TEST BANK| MEDICAL COLLEGE ADMISSION
TEST AAMC EXAM PREP WITH COMPLETE 400 REAL
EXAM QUESTIONS AND CORRECT VERIFIED
ANSWERS/ ALREADY GRADED A+ (MOST RECENT!!)
➢ Chemical and Physical Foundations of Biological Systems (Quest 1-100)
A researcher studies an enzyme-catalyzed reaction at 37°C. In the
absence of inhibitor, Vmax is 120 μmol/min and Km is 4.0 mM. A
competitive inhibitor is added at a concentration that doubles the
apparent Km without changing Vmax. At a substrate concentration of
4.0 mM, what reaction velocity should be expected?
A. 40 μmol/min
B. 60 μmol/min
C. 80 μmol/min
D. 120 μmol/min - Correct Answer - A. 40 μmol/min
Competitive inhibition doubles Km to 8.0 mM while Vmax remains 120
μmol/min. Using \(v=V_{max}[S]/(K_m+[S])\): \(v=120(4)/(8+4)=40\)
μmol/min.
During an experiment, a 0.020 mol sample of an ideal gas occupies 500
mL at 300 K. The gas is compressed isothermally until its volume is 125
mL. What is the final pressure if the initial pressure is 1.00 atm?
A. 0.25 atm
B. 2.00 atm
C. 4.00 atm
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D. 8.00 atm - Correct Answer - C. 4.00 atm
Temperature and amount of gas remain constant, so Boyle's law applies:
\(P_1V_1=P_2V_2\). Thus \(P_2=(1.00)(500/125)=4.00\) atm.
A weak acid HA has a pKa of 4.8. A buffer initially contains equal
concentrations of HA and A⁻. If the pH is increased to 5.8 while total
buffer concentration remains constant, which change occurs?
A. [HA] becomes 10 times [A⁻]
B. [A⁻] becomes 10 times [HA]
C. [A⁻] becomes equal to [HA]
D. [HA] becomes 100 times [A⁻] - Correct Answer - B. [A⁻] becomes 10
times [HA]
Henderson-Hasselbalch gives \(pH=pK_a+\log([A^-]/[HA])\). Since pH
− pKa = 1, the ratio is \(10^1=10\).
A 2.0-kg cart moves at 3.0 m/s on a horizontal frictionless track and
collides with a stationary 1.0-kg cart. The carts lock together after
impact. What is their combined speed immediately afterward?
A. 1.0 m/s
B. 1.5 m/s
C. 2.0 m/s
D. 3.0 m/s - Correct Answer - C. 2.0 m/s
Momentum is conserved: \((2.0)(3.0)+(1.0)(0)=(3.0)v\). Therefore,
\(v=2.0\) m/s.
Researchers place erythrocytes in three solutions. Solution X causes
cells to swell and lyse, solution Y produces no measurable change, and
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solution Z causes cells to shrink. Which relationship between the
solutions is most consistent with these observations?
A. X is hypotonic, Y is isotonic, Z is hypertonic
B. X is hypertonic, Y is hypotonic, Z is isotonic
C. X is isotonic, Y is hypertonic, Z is hypotonic
D. X is hypotonic, Y is hypertonic, Z is isotonic - Correct Answer - A. X
is hypotonic, Y is isotonic, Z is hypertonic
Water enters cells in hypotonic solutions, causing swelling. Isotonic
solutions produce no net water movement, while hypertonic solutions
cause water to leave cells.
A positively charged particle enters a uniform electric field with velocity
perpendicular to the field lines. Which trajectory will the particle follow
if magnetic effects and gravity are negligible?
A. A straight path parallel to the field
B. A circular path within the field
C. A parabolic path
D. A helical path around the field lines - Correct Answer - C. A parabolic
path
The electric force is constant and parallel to the electric field, producing
constant acceleration. With the initial velocity perpendicular to that
acceleration, the resulting trajectory is parabolic.
A patient receives an intravenous solution containing 0.90% NaCl.
Assuming NaCl dissociates completely into two ions, which property
primarily determines the solution's osmotic pressure?
A. Its total concentration of dissolved particles
B. The molecular mass of sodium chloride alone
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C. The density of the solvent alone
D. The electrical charge of chloride alone - Correct Answer - A. Its total
concentration of dissolved particles
Osmotic pressure is a colligative property dependent on the number of
dissolved particles. Complete NaCl dissociation increases the number of
osmotically active particles.
A reaction has ΔH = +85 kJ/mol and ΔS = +0.20 kJ/(mol·K). At what
temperature does the reaction become thermodynamically favorable
under standard conditions?
A. 213 K
B. 300 K
C. 425 K
D. 625 K - Correct Answer - C. 425 K
At the transition point, ΔG = 0. Therefore, \(T=\Delta H/\Delta
S=85/0.20=425\) K. Above this temperature, ΔG becomes negative.
A 1.0-L solution contains 0.10 mol of a monoprotic weak acid and 0.10
mol of its conjugate base. Which addition would most strongly resist a
subsequent small addition of strong acid?
A. 0.10 mol of water
B. 0.10 mol of the conjugate base
C. 0.10 mol of the weak acid
D. 0.10 mol of a neutral salt unrelated to the buffer - Correct Answer -
B. 0.10 mol of the conjugate base
The conjugate base directly reacts with added H⁺ to form the weak acid.
Increasing the conjugate-base reservoir therefore increases resistance to
added strong acid.
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