I85PREP
⌘ K
UNSA Medicine Entrance Exam study materials
UNSA Medicine Entrance Exam study resources

UNSA Medicine Entrance Exam practice questions

One question at a time. Build your UNSA Medicine Entrance Exam understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Biology

Which organelle is the principal site of ATP synthesis by oxidative phosphorylation in a eukaryotic cell?

  1. Golgi apparatus
  2. Mitochondrion Correct answer.
  3. Rough endoplasmic reticulum
  4. Lysosome

Explanation

The inner mitochondrial membrane carries the electron transport chain and ATP synthase, which together couple proton gradient dissipation to ATP production. This process, oxidative phosphorylation, supplies most of the ATP used by aerobic eukaryotic cells. Other organelles listed perform synthesis, digestion, or modification of proteins and lipids rather than bulk ATP generation.

Question 2Biology

During which phase of mitosis do sister chromatids separate and move toward opposite poles of the cell?

  1. Anaphase Correct answer.
  2. Prophase
  3. Metaphase
  4. Telophase

Explanation

Anaphase begins when the cohesin complex is cleaved and sister chromatids are pulled apart by shortening kinetochore microtubules. Each chromatid then becomes an independent chromosome moving toward a spindle pole. Prophase and metaphase precede this separation, while telophase follows it.

Question 3Biology

A human somatic cell in G1 phase contains 46 chromosomes. What is the DNA content of this cell relative to a haploid gamete of the same species?

  1. Equal to the haploid content
  2. Four times the haploid content
  3. Twice the haploid content Correct answer.
  4. Half the haploid content

Explanation

A G1 somatic cell is diploid, holding two chromosome sets, one from each parent. A gamete carries a single set after meiosis, so the diploid G1 DNA content is twice the haploid value. Replication in S phase would raise it to four times the haploid content temporarily.

Question 4Biology

Which molecule serves as the immediate energy currency that powers most cellular work, such as active transport and muscle contraction?

  1. ATP Correct answer.
  2. Pyruvate
  3. NADH
  4. Glucose

Explanation

ATP hydrolysis releases free energy that cells couple directly to endergonic processes such as ion pumping and contraction. Glucose and pyruvate are fuels that must be oxidized to generate ATP, and NADH is an electron carrier. Thus ATP is the shared intermediate between energy-yielding and energy-consuming reactions.

Question 5Biology

In Mendelian genetics, a cross between two heterozygotes (Aa x Aa) produces offspring with what expected phenotypic ratio when A is completely dominant over a?

  1. 9:3:3:1
  2. 1:2:1
  3. 3:1 Correct answer.
  4. 1:1

Explanation

Each heterozygote parent transmits A or a with equal probability, giving genotypic ratios of 1 AA : 2 Aa : 1 aa. Because A is completely dominant, both AA and Aa show the dominant phenotype, so the phenotypic ratio is 3 dominant to 1 recessive. The 1:2:1 ratio describes genotypes, not phenotypes.

Question 6Biology

Which blood vessel type has the thinnest walls and is the principal site of exchange of gases and nutrients with tissues?

  1. Arteriole
  2. Vein
  3. Capillary Correct answer.
  4. Artery

Explanation

Capillaries consist of a single layer of endothelial cells, which minimizes diffusion distance for gases, nutrients, and wastes. Their enormous total surface area and slow flow further favor exchange. Arteries and veins have thick muscular and connective walls suited to transport, not diffusion.

Question 7Biology

Which of the following is a polysaccharide used by plants as a structural component of cell walls?

  1. Cellulose Correct answer.
  2. Glycogen
  3. Chitin
  4. Starch

Explanation

Cellulose consists of long unbranched beta-1,4-linked glucose chains that associate into strong microfibrils, giving plant cell walls tensile strength. Starch is a plant storage polysaccharide, while glycogen is an animal storage form. Chitin is a structural polysaccharide of fungi and arthropods, not plants.

Question 8Biology

Which process describes the movement of water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration?

  1. Osmosis Correct answer.
  2. Diffusion
  3. Active transport
  4. Filtration

Explanation

Osmosis is the net movement of water across a semipermeable membrane down its own concentration gradient, which corresponds to moving toward the compartment with more solute. Diffusion describes solute movement without a membrane requirement, and active transport consumes ATP to move substances against gradients.

Question 9Biology

A patient's blood pH is measured at 7.30. Which statement best describes this value and the expected immediate physiological response?

  1. It is acidosis; ventilation increases to expel carbon dioxide Correct answer.
  2. It is acidosis; ventilation decreases to retain carbon dioxide
  3. It is normal; no respiratory adjustment is required
  4. It is alkalosis; breathing rate decreases to retain carbon dioxide

Explanation

Normal arterial pH is approximately 7.35 to 7.45, so 7.30 represents acidosis. Chemoreceptors detect the excess hydrogen ions and stimulate increased ventilation, which lowers carbon dioxide and shifts the bicarbonate buffer equilibrium to reduce acidity.

Question 10Biology

An enzyme catalyzes a reaction with a Michaelis constant (Km) of 5 mM. At a substrate concentration of 5 mM, what fraction of the maximum velocity is observed, assuming simple Michaelis-Menten kinetics?

  1. All of it
  2. One quarter
  3. One half Correct answer.
  4. One third

Explanation

The Michaelis-Menten equation gives v = Vmax[S]/(Km + [S]). Substituting [S] equal to Km yields v = Vmax/2, because the numerator and denominator differ only by the factor of two. Thus Km is by definition the substrate concentration supporting half-maximal velocity.

Question 11Biology

In a population at Hardy-Weinberg equilibrium, the frequency of the recessive allele is 0.2. What proportion of the population is expected to be heterozygous?

  1. 0.16
  2. 0.64
  3. 0.04
  4. 0.32 Correct answer.

Explanation

Heterozygote frequency is 2pq, where q equals 0.2 and p equals 0.8. Multiplying gives 2 x 0.8 x 0.2 = 0.32, so 32 percent of individuals are expected carriers. The value q squared, 0.04, represents homozygous recessive individuals instead.

Question 12Biology

Which statement correctly describes the role of tRNA in translation?

  1. It carries the genetic message from DNA to the ribosome
  2. It removes introns from pre-mRNA before translation begins
  3. It delivers amino acids matching its anticodon to the growing polypeptide Correct answer.
  4. It forms the structural core of the ribosome and catalyzes peptide bonds

Explanation

Each tRNA is charged with a specific amino acid and bears an anticodon that base-pairs with the complementary mRNA codon in the ribosome A site. This ensures the amino acid dictated by each codon is added in order. mRNA carries the message, rRNA forms the ribosome, and splicing is performed by snRNPs.

Question 13Biology

A woman who is a carrier of an X-linked recessive disorder has children with an unaffected man. What proportion of their sons is expected to be affected?

  1. One quarter
  2. None
  3. All
  4. One half Correct answer.

Explanation

Sons inherit their single X chromosome from the mother and a Y from the father. A carrier mother transmits the mutant X to half of her sons, and because males are hemizygous, each son receiving it is affected. Daughters instead receive the father's normal X, so none are affected in this cross.

Question 14Biology

Which feature distinguishes prokaryotic cells from eukaryotic cells?

  1. Prokaryotes lack a membrane-bound nucleus Correct answer.
  2. Prokaryotes lack a plasma membrane
  3. Prokaryotes lack nucleic acids
  4. Prokaryotes lack ribosomes

Explanation

Prokaryotes keep their chromosome in a nucleoid region without a nuclear envelope, whereas eukaryotes enclose DNA in a true nucleus. Prokaryotes still possess ribosomes, a plasma membrane, and DNA or RNA, so those features cannot distinguish the two groups. The presence of membrane-bound organelles is likewise eukaryotic.

Question 15Biology

During glycolysis, one molecule of glucose is converted to two molecules of pyruvate. What is the net yield of ATP and NADH per glucose under standard textbook accounting?

  1. 4 ATP and 2 NADH
  2. 2 ATP and 2 NADH Correct answer.
  3. 2 ATP and 4 NADH
  4. 4 ATP and 4 NADH

Explanation

Glycolysis consumes two ATP during the preparatory phase and produces four ATP during the payoff phase, giving a net gain of two ATP. Two molecules of NAD+ are reduced to NADH when glyceraldehyde-3-phosphate is oxidized. The gross figure of four ATP ignores the investment phase.

Question 16Biology

A mutation changes a single DNA base but the encoded amino acid sequence remains unchanged. What type of mutation is this?

  1. Missense mutation
  2. Frameshift mutation
  3. Nonsense mutation
  4. Silent mutation Correct answer.

Explanation

A silent mutation alters a codon but, owing to the degeneracy of the genetic code, still specifies the same amino acid. Missense mutations change one amino acid, nonsense mutations create a premature stop codon, and frameshifts shift the reading frame. Protein function is typically unaffected by silent changes.

Question 17Biology

Which structure of the human respiratory system is the primary site of gas exchange with the blood?

  1. Larynx
  2. Bronchus
  3. Alveolus Correct answer.
  4. Trachea

Explanation

Alveoli are tiny sacs with walls one cell thick, surrounded by dense capillary networks, so oxygen and carbon dioxide diffuse across a minimal barrier. Their combined surface area is very large, supporting efficient exchange. The trachea, bronchi, and larynx are conducting airways that do not carry out significant exchange.

Question 18Biology

In the cardiac cycle, which event immediately follows the closure of the atrioventricular valves?

  1. Opening of the semilunar valves
  2. Ventricular ejection
  3. Atrial filling
  4. Isovolumetric ventricular contraction Correct answer.

Explanation

When the atrioventricular valves close at the start of systole, all valves are briefly shut while ventricular pressure rises. This isovolumetric contraction phase ends only when ventricular pressure exceeds aortic and pulmonary pressure, opening the semilunar valves and beginning ejection. Ejection therefore follows, rather than coincides with, valve closure.

Question 19Biology

Which hormone is released by the posterior pituitary and acts to increase water reabsorption in the collecting ducts of the kidney?

  1. Insulin
  2. Aldosterone
  3. Atrial natriuretic peptide
  4. Antidiuretic hormone Correct answer.

Explanation

Antidiuretic hormone, also called vasopressin, is released from the posterior pituitary and inserts aquaporin channels into collecting duct membranes. This increases water reabsorption and concentrates urine. Aldosterone instead promotes sodium reabsorption, and atrial natriuretic peptide promotes sodium and water excretion.

Question 20Biology

In the light-dependent reactions of photosynthesis, what is the immediate source of electrons that replace those lost by photosystem II?

  1. ATP
  2. Carbon dioxide
  3. NADPH
  4. Water Correct answer.

Explanation

Photosystem II oxidizes water at the oxygen-evolving complex, splitting it into electrons, protons, and oxygen. The extracted electrons replace those excited from the reaction center chlorophyll. NADPH is a product of the electron transport chain, and carbon dioxide is fixed later in the Calvin cycle.

Question 21Biology

Which statement best explains why the genetic code is described as degenerate?

  1. The code differs substantially among species
  2. Each codon can specify several different amino acids
  3. Codons are read in overlapping triplets
  4. Most amino acids are specified by more than one codon Correct answer.

Explanation

Degeneracy means that multiple codons can encode the same amino acid, which buffers against some point mutations. The code is nonetheless unambiguous, since each codon corresponds to only one amino acid. Reading is non-overlapping and the code is nearly universal across organisms.

Question 22Biology

A cell is placed in a hypertonic solution. What immediate osmotic response is expected in an animal cell?

  1. Solutes move out to equalize concentration
  2. No net water movement occurs
  3. Water enters and the cell swells
  4. Water leaves and the cell shrinks Correct answer.

Explanation

A hypertonic solution has a higher solute concentration than the cytoplasm, so water exits the cell by osmosis. Animal cells lack a rigid wall and therefore shrink, a process called crenation. Solute movement does not occur freely across the membrane, so water movement drives the change.

Question 23Biology

A dihybrid cross between two individuals heterozygous for both genes (AaBb x AaBb) yields offspring. Assuming independent assortment and complete dominance, what fraction is expected to show both recessive phenotypes?

  1. 9/16
  2. 1/4
  3. 1/16 Correct answer.
  4. 3/16

Explanation

Each gene behaves as a monohybrid cross, so the probability of the recessive phenotype at one locus is 1/4. Because the loci assort independently, the joint probability is the product, 1/4 x 1/4 = 1/16. The 9:3:3:1 ratio assigns this fraction to the double-recessive class.

Question 24Biology

An individual with genotype IAi and an individual with genotype IBi have children. Which blood types can appear among their offspring?

  1. Only type O
  2. Only type A and type B
  3. Only type AB
  4. Types A, B, AB, and O Correct answer.

Explanation

The IA and IB alleles are codominant, and both are dominant to i. Gametes from the parents combine to give IAIB (type AB), IAi (type A), IBi (type B), and ii (type O), each with probability one quarter. All four ABO phenotypes are therefore possible.

Question 25Biology

A competitive inhibitor is added to an enzyme-catalyzed reaction. Which kinetic change is expected?

  1. Both Km and Vmax decrease
  2. Km decreases while Vmax is unchanged
  3. Km increases while Vmax is unchanged Correct answer.
  4. Vmax decreases while Km is unchanged

Explanation

A competitive inhibitor binds the free enzyme's active site and can be outcompeted by raising substrate concentration. This raises the apparent Km because more substrate is needed to reach half-maximal velocity, but saturating substrate still achieves the original Vmax. Noncompetitive inhibitors instead lower Vmax without changing Km.

Question 26Biology

Which organelle is the principal site of ATP production by oxidative phosphorylation in a eukaryotic cell?

  1. The mitochondrion Correct answer.
  2. The Golgi apparatus
  3. The lysosome
  4. The smooth endoplasmic reticulum

Explanation

The inner mitochondrial membrane carries the electron transport chain and ATP synthase, so most ATP from oxidative phosphorylation is generated there. The other organelles listed perform sorting, digestion, or lipid synthesis rather than bulk ATP synthesis.

Question 27Biology

Which molecule serves as the immediate energy currency that directly powers most cellular work, such as active transport and muscle contraction?

  1. ATP Correct answer.
  2. Glucose
  3. NADH
  4. Cholesterol

Explanation

ATP couples exergonic reactions to endergonic ones by transferring its terminal phosphate group, releasing usable energy. Glucose and NADH store energy that must first be converted to ATP before most cellular work proceeds.

Question 28Biology

A DNA template strand reads 3'-TAC-5'. Following complementary base pairing, which mRNA codon is transcribed from this triplet?

  1. 5'-AUG-3' Correct answer.
  2. 5'-UAC-3'
  3. 5'-TAC-3'
  4. 5'-ATG-3'

Explanation

RNA polymerase builds mRNA complementary and antiparallel to the template, pairing adenine with uracil. The template 3'-TAC-5' therefore yields 5'-AUG-3', which also serves as a start codon.

Question 29Biology

Which statement best describes the role of the sodium-potassium pump in a resting neuron?

  1. It allows sodium and potassium to diffuse freely down their gradients without energy input
  2. It transports chloride ions inward to hyperpolarize the membrane
  3. It moves three sodium ions in and two potassium ions out per ATP, directly generating the action potential
  4. It moves three sodium ions out and two potassium ions in per ATP, helping maintain the resting potential Correct answer.

Explanation

The pump uses one ATP to export three sodium ions and import two potassium ions, creating steep electrochemical gradients. This electrogenic, unequal exchange contributes a small negative charge to the resting membrane potential.

Question 30Biology

A couple in which both partners are heterozygous for an autosomal recessive disorder have a child. What is the probability that the child is an affected homozygote?

  1. 1/4 Correct answer.
  2. 3/4
  3. 1/2
  4. 0

Explanation

Two heterozygotes (Aa x Aa) produce offspring in a 1 AA : 2 Aa : 1 aa ratio. Only the aa genotype is affected, so the probability is one quarter.

Question 31Biology

Which of the following best describes the concept of genetic drift?

  1. The movement of alleles between populations through migration
  2. A change in allele frequencies caused by nonrandom mating
  3. A directional change in allele frequencies caused by natural selection
  4. A random change in allele frequencies due to chance events, especially in small populations Correct answer.

Explanation

Genetic drift is sampling error in allele frequencies across generations, and its effects are strongest in small populations. It differs from selection, which is nonrandom and fitness-driven, and from gene flow, which involves migration.

Question 32Biology

Which of the following best characterizes the role of the Calvin cycle in photosynthesis?

  1. It uses light energy directly to split water and release oxygen
  2. It fixes carbon dioxide into organic molecules using ATP and NADPH Correct answer.
  3. It generates a proton gradient across the thylakoid membrane
  4. It transfers electrons from photosystem II to photosystem I

Explanation

The Calvin cycle is light-independent in the sense that it uses ATP and NADPH from the light reactions to fix carbon dioxide into sugars. Water splitting and electron transfer belong to the light-dependent reactions.

Question 33Biology

In the human nephron, in which segment is the majority of filtered water reabsorbed?

  1. The collecting duct
  2. The distal convoluted tubule
  3. The proximal convoluted tubule Correct answer.
  4. The descending limb of the loop of Henle

Explanation

About two thirds of filtered water and sodium is reabsorbed in the proximal convoluted tubule, largely following active solute transport. Later segments fine-tune water balance under hormonal control.

Question 34Biology

Which of the following is a function of the sinoatrial node in the heart?

  1. It conducts impulses from the atria to the ventricles
  2. It acts as the pacemaker, initiating electrical impulses that set the heart rate Correct answer.
  3. It contracts to eject blood into the aorta
  4. It delays impulses to allow the atria to empty before ventricular contraction

Explanation

The sinoatrial node spontaneously depolarizes and sets the rhythm, making it the natural pacemaker. The atrioventricular node delays and relays impulses, while ventricular muscle performs ejection.

Question 35Biology

In a food chain, approximately what proportion of energy at one trophic level is typically transferred to the next?

  1. About 50 percent
  2. About 90 percent
  3. About 10 percent Correct answer.
  4. About 1 percent

Explanation

Roughly ten percent of energy is passed to the next trophic level, with the rest lost mainly as heat through respiration. This low efficiency limits food chains to a few levels.

Question 36Biology

A competitive inhibitor binds to the active site of an enzyme. Which kinetic effect is expected when substrate concentration is varied?

  1. Both Km and Vmax increase
  2. The apparent Km increases while Vmax remains unchanged Correct answer.
  3. Vmax decreases while Km stays the same
  4. Both Km and Vmax decrease proportionally

Explanation

A competitive inhibitor competes with substrate for the active site, so more substrate is needed to reach half-maximal velocity, raising apparent Km. Because inhibition can be overcome at high substrate concentration, Vmax is unchanged.

Question 37Biology

In a human somatic cell at metaphase of mitosis, how many chromatids are present, assuming a normal diploid chromosome number of 46?

  1. 23
  2. 92 Correct answer.
  3. 46
  4. 184

Explanation

After DNA replication in S phase, each of the 46 chromosomes consists of two sister chromatids. At metaphase these are still attached, giving 92 chromatids in total.

Question 38Biology

A mutation inserts one nucleotide into the coding region of a gene. Which consequence is most likely?

  1. A silent mutation with no change to the protein
  2. A change in the reading frame limited to one codon
  3. A single amino acid substitution only
  4. A frameshift that alters all downstream amino acids Correct answer.

Explanation

Inserting a single nucleotide shifts the reading frame from that point onward, changing every subsequent codon. This usually produces a truncated or nonfunctional protein.

Question 39Biology

Which of the following best explains why the human population can grow exponentially under ideal conditions?

  1. Birth rates exceed death rates and resources are unlimited Correct answer.
  2. Death rates always exceed birth rates
  3. Emigration constantly removes individuals
  4. Carrying capacity is reached immediately

Explanation

Exponential growth occurs when per capita growth rate is positive and resources do not limit reproduction, so births outpace deaths. Once resources become limiting, growth slows and approaches carrying capacity.

Question 40Biology

During the light-independent reactions of photosynthesis, a plant cell is supplied with carbon dioxide labeled with carbon-14. Into which of the following molecules is this labeled carbon most directly incorporated first?

  1. 3-phosphoglycerate Correct answer.
  2. Glucose
  3. Pyruvate
  4. Ribulose bisphosphate

Explanation

In the Calvin cycle, the enzyme rubisco attaches CO2 to the five-carbon acceptor ribulose bisphosphate, and the unstable six-carbon intermediate immediately splits into two molecules of 3-phosphoglycerate. Therefore the first stable molecule to contain the newly fixed labeled carbon is 3-phosphoglycerate, which is later reduced and used to regenerate the acceptor and to build sugars.

Question 41Chemistry

What is the chemical formula of sulfuric acid?

  1. H2SO4 Correct answer.
  2. H2S
  3. HSO4
  4. H2SO3

Explanation

Sulfuric acid contains two hydrogen atoms, one sulfur atom, and four oxygen atoms, giving the formula H2SO4. The sulfate ion carries a 2- charge, so two hydrogen ions are needed to balance it.

Question 42Chemistry

How many protons does a neutral atom of carbon-14 contain?

  1. 12
  2. 6 Correct answer.
  3. 8
  4. 14

Explanation

The atomic number of carbon is 6, and the atomic number equals the number of protons in the nucleus. The mass number 14 only reflects protons plus neutrons, so carbon-14 has 6 protons and 8 neutrons.

Question 43Chemistry

Which type of bond forms between sodium and chlorine in sodium chloride?

  1. Hydrogen
  2. Covalent
  3. Metallic
  4. Ionic Correct answer.

Explanation

Sodium is a metal that loses an electron to become a cation, while chlorine is a nonmetal that gains that electron to become an anion. The electrostatic attraction between these oppositely charged ions is an ionic bond.

Question 44Chemistry

In the reaction 2H2 + O2 -> 2H2O, how many moles of water form from 3 moles of H2 with excess O2?

  1. 6
  2. 3 Correct answer.
  3. 1.5
  4. 2

Explanation

The balanced equation shows that 2 moles of H2 produce 2 moles of water, a 1:1 ratio. Therefore 3 moles of hydrogen yield 3 moles of water when oxygen is in excess.

Question 45Chemistry

What is the pH of a solution with a hydrogen ion concentration of 1 x 10^-3 mol/L?

  1. 7
  2. 11
  3. 3 Correct answer.
  4. 10

Explanation

pH is defined as the negative base-10 logarithm of the hydrogen ion concentration. The log of 1 x 10^-3 is -3, so the pH is 3, which indicates an acidic solution.

Question 46Chemistry

Which functional group characterizes alcohols?

  1. Amino group
  2. Hydroxyl group Correct answer.
  3. Carboxyl group
  4. Carbonyl group

Explanation

Alcohols contain a hydroxyl group, written as -OH, bonded to a carbon atom. This group distinguishes alcohols from other families such as carboxylic acids and amines.

Question 47Chemistry

Which of the following is a noble gas?

  1. Nitrogen
  2. Oxygen
  3. Argon Correct answer.
  4. Chlorine

Explanation

Argon belongs to group 18 of the periodic table, whose elements are the noble gases. These atoms have full outer electron shells, making them highly unreactive.

Question 48Chemistry

Which process describes a solid changing directly into a gas?

  1. Sublimation Correct answer.
  2. Evaporation
  3. Deposition
  4. Condensation

Explanation

Sublimation is the phase change in which a solid becomes a gas without passing through the liquid state. Dry ice and iodine are common examples of substances that sublime.

Question 49Chemistry

What is the oxidation state of sulfur in the sulfate ion, SO4^2-?

  1. +2
  2. -2
  3. +6 Correct answer.
  4. +4

Explanation

Each oxygen is assigned -2, giving a total of -8 for four oxygen atoms. Since the ion carries a -2 charge, sulfur must be +6 so that +6 plus -8 equals -2.

Question 50Chemistry

Which element has the electron configuration 1s2 2s2 2p6 3s2?

  1. Aluminum
  2. Neon
  3. Sodium
  4. Magnesium Correct answer.

Explanation

Counting the electrons gives 2 + 2 + 6 + 2 = 12, and the element with atomic number 12 is magnesium. The configuration ends in the 3s subshell, consistent with an alkaline earth metal.