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NMCB Licensure Exam practice questions

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Question 1Basic Sciences Foundations

Which organelle is the primary site of ATP production through oxidative phosphorylation in a eukaryotic cell?

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

Explanation

The inner mitochondrial membrane houses the electron transport chain and ATP synthase, which together generate most cellular ATP via oxidative phosphorylation. Other organelles listed perform packaging, degradation, or lipid synthesis rather than bulk ATP synthesis.

Question 2Basic Sciences Foundations

A red blood cell placed in a 0.45% sodium chloride solution will most likely do which of the following?

  1. Shrink because water leaves the cell
  2. Undergo crenation from solute influx
  3. Swell because water enters the cell Correct answer.
  4. Remain unchanged because the solution is isotonic

Explanation

A 0.45% NaCl solution is hypotonic relative to intracellular fluid, so water moves into the cell by osmosis down its concentration gradient. Because red blood cells lack a rigid wall, the incoming water causes them to swell and potentially hemolyze.

Question 3Basic Sciences Foundations

Which molecule serves as the immediate energy currency that directly powers most cellular work?

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

Explanation

ATP hydrolysis releases a phosphate group and free energy that cells couple directly to endergonic reactions such as transport and synthesis. Glucose and NADH store energy but must first be converted through metabolic pathways before that energy is usable.

Question 4Basic Sciences Foundations

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

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

Explanation

Anaphase begins when cohesin is cleaved and sister chromatids are pulled apart by spindle fibers toward opposite poles. Prophase involves condensation, metaphase involves alignment at the equator, and telophase involves nuclear reformation.

Question 5Basic Sciences Foundations

Which of the following best describes the function of DNA polymerase during replication?

  1. It joins Okazaki fragments together
  2. It unwinds the double helix ahead of the fork
  3. It synthesizes new DNA strands using a template Correct answer.
  4. It removes RNA primers and replaces them

Explanation

DNA polymerase adds complementary nucleotides to a growing strand in a template-directed manner, extending the new DNA chain. Unwinding is performed by helicase, primer removal by RNase H or polymerase exonuclease activity, and fragment joining by ligase.

Question 6Basic Sciences Foundations

A patient has a mutation that prevents the synthesis of the amino acid tyrosine. Which precursor molecule is directly deficient in this pathway?

  1. Phenylalanine Correct answer.
  2. Tryptophan
  3. Glutamate
  4. Histidine

Explanation

Tyrosine is synthesized from phenylalanine through hydroxylation catalyzed by phenylalanine hydroxylase. A block in this conversion leads to phenylalanine accumulation and tyrosine deficiency, as seen in phenylketonuria.

Question 7Basic Sciences Foundations

Which of the following is the principal function of the sodium-potassium pump in maintaining resting membrane potential?

  1. It allows both ions to diffuse freely across the membrane
  2. It moves sodium and potassium down their concentration gradients
  3. It exports three sodium ions while importing two potassium ions Correct answer.
  4. It imports three sodium ions while exporting two potassium ions

Explanation

The Na+/K+-ATPase uses ATP to pump three sodium ions out of the cell and two potassium ions into the cell against their gradients. This electrogenic action contributes to the negative resting membrane potential and maintains ionic gradients.

Question 8Basic Sciences Foundations

Which enzyme catalyzes the rate-limiting step of glycolysis?

  1. Pyruvate kinase
  2. Hexokinase
  3. Phosphofructokinase-1 Correct answer.
  4. Aldolase

Explanation

Phosphofructokinase-1 catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, the committed and rate-limiting step of glycolysis. It is tightly regulated by energy charge indicators such as ATP and AMP.

Question 9Basic Sciences Foundations

Which component of the cytoskeleton is primarily responsible for forming the mitotic spindle?

  1. Intermediate filaments
  2. Collagen fibers
  3. Microtubules Correct answer.
  4. Actin filaments

Explanation

Microtubules, composed of alpha and beta tubulin dimers, assemble into the spindle apparatus that segregates chromosomes during mitosis. Actin filaments and intermediate filaments serve different structural and contractile roles.

Question 10Basic Sciences Foundations

A deficiency in vitamin B12 would most directly impair which of the following processes?

  1. Conversion of pyruvate to acetyl-CoA
  2. Synthesis of glycogen from glucose
  3. Conversion of methylmalonyl-CoA to succinyl-CoA Correct answer.
  4. Oxidation of fatty acids in the mitochondria

Explanation

Vitamin B12 is a cofactor for methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. Deficiency leads to accumulation of methylmalonic acid, a recognized diagnostic marker.

Question 11Basic Sciences Foundations

Which of the following best describes the role of tRNA in protein synthesis?

  1. It catalyzes peptide bond formation
  2. It forms the structural core of the ribosome
  3. It carries the genetic message from DNA to the ribosome
  4. It delivers specific amino acids to the ribosome Correct answer.

Explanation

Transfer RNA molecules recognize codons on mRNA through their anticodons and deliver the corresponding amino acids to the growing polypeptide chain. Messenger RNA carries the genetic message, and ribosomal RNA forms the catalytic core.

Question 12Basic Sciences Foundations

In Mendelian genetics, a cross between two heterozygous individuals (Aa x Aa) is expected to produce which phenotypic ratio for a completely dominant trait?

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

Explanation

A monohybrid cross of two heterozygotes yields a genotypic ratio of 1 AA : 2 Aa : 1 aa, which collapses to a 3:1 phenotypic ratio when the dominant allele masks the recessive. The 1:2:1 ratio describes genotypes, not phenotypes.

Question 13Basic Sciences Foundations

Which of the following chromosomal abnormalities describes the presence of three copies of chromosome 21?

  1. Monosomy
  2. Trisomy Correct answer.
  3. Deletion
  4. Translocation

Explanation

Trisomy refers to the presence of three copies of a particular chromosome instead of the normal two, as seen in trisomy 21 (Down syndrome). Monosomy is one copy, while deletion and translocation involve structural changes.

Question 14Basic Sciences Foundations

Which of the following is the correct base-pairing rule in DNA?

  1. Adenine pairs with guanine
  2. Adenine pairs with thymine Correct answer.
  3. Guanine pairs with uracil
  4. Thymine pairs with cytosine

Explanation

In DNA, adenine forms two hydrogen bonds with thymine, and guanine forms three with cytosine. Uracil replaces thymine in RNA, so guanine-uracil pairing does not occur in DNA.

Question 15Basic Sciences Foundations

A patient with chronic alcoholism presents with hypoglycemia and elevated lactate. Which metabolic process is most directly impaired?

  1. Lipogenesis
  2. Ketogenesis
  3. Glycogenolysis
  4. Gluconeogenesis Correct answer.

Explanation

Chronic alcohol metabolism increases the NADH/NAD+ ratio, which shifts the lactate dehydrogenase reaction toward lactate and impairs gluconeogenic substrate availability. The resulting inability to maintain glucose production causes hypoglycemia.

Question 16Basic Sciences Foundations

Which of the following best explains why enzymes lower the activation energy of a reaction?

  1. They stabilize the transition state of the reaction Correct answer.
  2. They permanently consume reactants in side reactions
  3. They change the equilibrium constant of the reaction
  4. They increase the temperature of the reaction mixture

Explanation

Enzymes provide a microenvironment that preferentially binds and stabilizes the transition state, lowering the energy barrier without altering the reaction's overall free-energy change. Enzymes do not change equilibrium constants or consume reactants.

Question 17Basic Sciences Foundations

Which of the following best describes the inheritance pattern of an X-linked recessive disorder in a family?

  1. Affected fathers pass the trait to all daughters
  2. Males and females are affected with equal frequency
  3. Affected fathers pass the trait to all sons
  4. Affected mothers pass the trait to half of their sons Correct answer.

Explanation

A male inherits his single X chromosome from his mother, so an affected carrier mother has a 50% chance of transmitting the mutant allele to each son. Fathers pass their Y chromosome to sons, so affected fathers do not transmit X-linked traits to sons.

Question 18Basic Sciences Foundations

Which of the following is the primary function of the sodium-glucose cotransporter in the intestinal epithelium?

  1. It transports glucose and sodium into the cell together Correct answer.
  2. It actively pumps glucose against its gradient using ATP
  3. It converts glucose to glycogen for storage
  4. It exports glucose from the cell into the blood

Explanation

The sodium-glucose cotransporter uses the sodium gradient established by the Na+/K+ pump to move glucose into the cell against its concentration gradient via secondary active transport. It does not directly hydrolyze ATP.

Question 19Basic Sciences Foundations

Which of the following describes the function of the promoter region in a gene?

  1. It binds RNA polymerase to initiate transcription Correct answer.
  2. It encodes the amino acid sequence of the protein
  3. It is removed from the mRNA by splicing
  4. It signals the end of transcription

Explanation

The promoter is a DNA sequence upstream of the coding region that provides a binding site for RNA polymerase and associated transcription factors, thereby initiating transcription. Coding regions encode amino acids, and terminators signal the end.

Question 20Basic Sciences Foundations

A researcher observes that a metabolic reaction proceeds at a much higher rate in the presence of an enzyme but reaches the same final equilibrium concentrations. Which principle does this illustrate?

  1. Enzymes alter the equilibrium constant of a reaction
  2. Enzymes increase the free energy released by a reaction
  3. Enzymes lower activation energy without changing equilibrium Correct answer.
  4. Enzymes are consumed in proportion to the reaction rate

Explanation

Enzymes accelerate both forward and reverse rates by lowering the activation energy, so equilibrium is reached faster but the equilibrium constant and final concentrations remain unchanged. Catalysts are regenerated and do not alter the thermodynamics of the reaction.

Question 21Basic Sciences Foundations

Which of the following best describes the consequence of a deficiency in vitamin C?

  1. Impaired collagen synthesis leading to poor wound healing Correct answer.
  2. Impaired blood clotting due to reduced prothrombin
  3. Impaired night vision due to reduced rhodopsin
  4. Impaired calcium absorption leading to rickets

Explanation

Vitamin C is required as a cofactor for prolyl and lysyl hydroxylases, which cross-link collagen. Deficiency impairs collagen synthesis and leads to scurvy, with poor wound healing and bleeding gums.

Question 22Basic Sciences Foundations

Which of the following statements about the genetic code is correct?

  1. Each amino acid is encoded by exactly one codon
  2. The code is degenerate, with multiple codons specifying some amino acids Correct answer.
  3. The code differs substantially between humans and bacteria
  4. Codons are read in overlapping triplets during translation

Explanation

The genetic code is degenerate, meaning most amino acids are specified by more than one codon, which provides some protection against point mutations. Codons are read as non-overlapping triplets, and the code is nearly universal across organisms.

Question 23Basic Sciences Foundations

A cell is treated with a drug that inhibits the electron transport chain. Which of the following is the most immediate consequence?

  1. Reduced proton gradient across the inner mitochondrial membrane Correct answer.
  2. Increased oxygen consumption by complex IV
  3. Enhanced glycolysis-independent ATP generation
  4. Increased ATP production via oxidative phosphorylation

Explanation

Electron transport chain complexes pump protons to establish the gradient that drives ATP synthase. Inhibiting the chain reduces proton pumping, dissipating the gradient and decreasing ATP production. Oxygen consumption by complex IV also falls.

Question 24Basic Sciences Foundations

Which of the following describes the role of the ribosome in protein synthesis?

  1. It stores genetic information in the nucleus
  2. It degrades misfolded proteins in the cytoplasm
  3. It assembles amino acids into a polypeptide chain Correct answer.
  4. It transports amino acids through the bloodstream

Explanation

The ribosome is the molecular machine that reads mRNA codons and catalyzes peptide bond formation to assemble amino acids into a polypeptide. It does not store genetic information, transport amino acids in blood, or degrade proteins.

Question 25Basic Sciences Foundations

Which of the following best explains why a frameshift mutation often produces a nonfunctional protein?

  1. It alters the reading frame, changing all downstream codons Correct answer.
  2. It deletes an entire chromosome segment
  3. It prevents transcription from occurring
  4. It substitutes one amino acid for another at a single position

Explanation

Insertion or deletion of a number of nucleotides not divisible by three shifts the reading frame, so every codon downstream is read differently. This typically produces a truncated or completely different amino acid sequence, destroying protein function.

Question 26Basic Sciences Foundations

Which of the following best describes the primary role of the plasma membrane in a typical human cell?

  1. It selectively regulates the movement of substances into and out of the cell. Correct answer.
  2. It serves as the main site of ATP production for the cell.
  3. It stores genetic material in the form of chromatin.
  4. It synthesizes ribosomal RNA for protein assembly.

Explanation

The plasma membrane is a phospholipid bilayer studded with proteins that controls what enters and exits the cell, maintaining a distinct internal environment. Its selective permeability underlies ion gradients, nutrient uptake, and waste removal. The other listed functions belong to mitochondria, the nucleolus, and the nucleus respectively.

Question 27Basic Sciences Foundations

A red blood cell is placed in a solution that is hypotonic relative to the cytoplasm. Which of the following is the most likely result?

  1. The cell shrinks as water leaves the cytoplasm.
  2. The cell swells as water enters the cytoplasm. Correct answer.
  3. The cell maintains its volume because no net water movement occurs.
  4. The cell actively pumps water out to preserve its shape.

Explanation

Water moves by osmosis from an area of lower solute concentration to an area of higher solute concentration. In a hypotonic solution, the surrounding fluid has less solute than the cytoplasm, so water enters the cell and it swells, potentially leading to hemolysis. Cells do not actively pump water; water movement is passive and follows osmotic gradients.

Question 28Basic Sciences Foundations

Which of the following best describes the role of the Golgi apparatus in the cell?

  1. It modifies, sorts, and packages proteins and lipids for transport. Correct answer.
  2. It generates the majority of cellular ATP through oxidative reactions.
  3. It degrades damaged organelles through hydrolytic enzymes.
  4. It synthesizes the ribosomal subunits used for translation.

Explanation

The Golgi apparatus receives proteins and lipids from the endoplasmic reticulum, chemically modifies them, and sorts them into vesicles destined for secretion, the plasma membrane, or lysosomes. It functions as the cell's distribution center. ATP generation, organelle degradation, and ribosomal subunit assembly are performed by other structures.

Question 29Basic Sciences Foundations

During which phase of the cell cycle does DNA replication occur?

  1. S phase Correct answer.
  2. G2 phase
  3. M phase
  4. G1 phase

Explanation

The cell cycle's S phase (synthesis phase) is when the genome is duplicated, producing two sister chromatids for each chromosome. G1 and G2 are gap phases of growth and preparation, while M phase is when chromosomes are segregated and the cell divides. DNA replication must precede mitosis so each daughter cell receives a complete genome.

Question 30Basic Sciences Foundations

A competitive inhibitor is added to an enzyme-catalyzed reaction. Which of the following changes in kinetic parameters is expected?

  1. A decreased Vmax with decreased Km
  2. A decreased Vmax with unchanged Km
  3. An increased Km with unchanged Vmax Correct answer.
  4. A decreased Km with unchanged Vmax

Explanation

A competitive inhibitor binds the active site reversibly, so it can be outcompeted by raising substrate concentration. This raises the apparent Km (lower apparent affinity) while Vmax remains attainable at very high substrate levels. Noncompetitive inhibitors instead lower Vmax without changing Km.

Question 31Basic Sciences Foundations

Which of the following best explains the role of NAD+ in glycolysis?

  1. It accepts electrons during the oxidation of glyceraldehyde-3-phosphate. Correct answer.
  2. It donates phosphate groups to glucose during the energy-investment phase.
  3. It transports pyruvate into the mitochondria for further oxidation.
  4. It directly phosphorylates ADP to form ATP at the end of glycolysis.

Explanation

During glycolysis, glyceraldehyde-3-phosphate is oxidized to 1,3-bisphosphoglycerate, and NAD+ is reduced to NADH as it accepts the electrons and a proton. This regeneration of NAD+ is essential for glycolysis to continue. ATP generation occurs by substrate-level phosphorylation, not by NAD+.

Question 32Basic Sciences Foundations

A patient's muscle biopsy shows impaired fatty acid oxidation. Which of the following organelles is most directly responsible for this defect?

  1. Mitochondria Correct answer.
  2. Lysosomes
  3. Golgi apparatus
  4. Rough endoplasmic reticulum

Explanation

Fatty acid beta-oxidation occurs in the mitochondrial matrix, where acyl-CoA is broken down to acetyl-CoA, NADH, and FADH2. Defects in mitochondrial transport or enzymes therefore impair fatty acid oxidation. The rough ER, Golgi, and lysosomes perform protein synthesis, sorting, and degradation rather than fatty acid catabolism.

Question 33Basic Sciences Foundations

Which of the following statements about the difference between DNA and RNA is correct?

  1. DNA contains deoxyribose, whereas RNA contains ribose. Correct answer.
  2. DNA contains adenine and guanine, whereas RNA contains cytosine and uracil.
  3. DNA is typically single-stranded, whereas RNA is double-stranded.
  4. DNA contains uracil, whereas RNA contains thymine.

Explanation

The sugar in DNA is deoxyribose, which lacks a hydroxyl group at the 2' carbon, while RNA contains ribose with that 2'-OH. This chemical difference affects stability and structure. DNA additionally uses thymine instead of uracil and is usually double-stranded, while RNA is usually single-stranded.

Question 34Basic Sciences Foundations

A frameshift mutation is introduced near the beginning of a coding sequence. Which of the following is the most likely consequence?

  1. The reading frame is shifted, so many downstream codons are altered. Correct answer.
  2. A premature stop codon is always created immediately at the mutation site.
  3. The mutation has no effect because the code is degenerate.
  4. A single amino acid is substituted with no downstream effect.

Explanation

Insertions or deletions that are not multiples of three shift the reading frame, so every codon after the mutation is read differently. This typically produces a truncated or completely different protein. Degeneracy protects against some single-base substitutions but cannot preserve the frame after such an insertion or deletion.

Question 35Basic Sciences Foundations

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

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

Explanation

With q = 0.2, p = 1 - q = 0.8. Heterozygote frequency is 2pq = 2(0.8)(0.2) = 0.32. The value 0.04 is q squared (homozygous recessive) and 0.64 is p squared (homozygous dominant).

Question 36Basic Sciences Foundations

Which of the following best describes the difference between mitosis and meiosis?

  1. Mitosis halves the chromosome number, whereas meiosis preserves the chromosome number.
  2. Mitosis involves crossing over, whereas meiosis does not involve any recombination.
  3. Mitosis produces four haploid cells, whereas meiosis produces two diploid cells.
  4. Mitosis produces two genetically identical diploid cells, whereas meiosis produces four genetically varied haploid cells. Correct answer.

Explanation

Mitosis is a single division yielding two daughter cells with the same chromosome number and genetic content as the parent. Meiosis involves two divisions plus crossing over and independent assortment, producing four haploid cells that are genetically distinct. This difference underlies somatic growth versus gamete formation.

Question 37Basic Sciences Foundations

A drug prevents the release of calcium from the sarcoplasmic reticulum in skeletal muscle. Which of the following is the most direct consequence?

  1. Actin and myosin cross-bridge cycling cannot be initiated. Correct answer.
  2. Acetylcholine release from the motor neuron is blocked.
  3. ATP synthesis in the muscle fiber stops immediately.
  4. The muscle fiber cannot generate an action potential.

Explanation

Calcium released from the sarcoplasmic reticulum binds troponin, moving tropomyosin to expose myosin-binding sites on actin and permitting cross-bridge cycling. Without calcium release, contraction cannot be triggered even though the action potential has propagated. Action potential generation and neurotransmitter release occur upstream of calcium release from the sarcoplasmic reticulum.

Question 38Basic Sciences Foundations

Which of the following best describes the function of hemoglobin in oxygen transport?

  1. It binds oxygen in tissues and releases it in the lungs.
  2. It converts carbon dioxide to bicarbonate in the plasma.
  3. It binds oxygen in the lungs and releases it in peripheral tissues. Correct answer.
  4. It transports glucose from the liver to peripheral tissues.

Explanation

Hemoglobin binds oxygen with high affinity in the oxygen-rich pulmonary capillaries and releases it in tissues where oxygen tension is lower. Cooperative binding produces the sigmoidal oxygen dissociation curve and facilitates unloading. Carbon dioxide transport and glucose carriage are separate processes.

Question 39Basic Sciences Foundations

A patient has a tumor that secretes excessive parathyroid hormone-related peptide (PTHrP). Which of the following laboratory patterns is most consistent with this condition?

  1. Hypercalcemia with high parathyroid hormone
  2. Hypocalcemia with low parathyroid hormone
  3. Hypercalcemia with low parathyroid hormone Correct answer.
  4. Hypocalcemia with high parathyroid hormone

Explanation

PTHrP mimics parathyroid hormone by increasing bone resorption and renal calcium reabsorption, producing hypercalcemia. Because the calcium rise is driven by the tumor peptide rather than the parathyroid glands, endogenous parathyroid hormone is suppressed through negative feedback. This pattern of hypercalcemia with low PTH is characteristic of humoral hypercalcemia of malignancy.

Question 40Basic Sciences Foundations

Which of the following best describes the role of the loop of Henle in urine concentration?

  1. It actively secretes glucose into the tubular fluid.
  2. It reabsorbs the majority of filtered bicarbonate.
  3. It filters plasma proteins from the blood into the tubule.
  4. It establishes a medullary osmotic gradient that allows water reabsorption. Correct answer.

Explanation

The countercurrent multiplier of the loop of Henle creates a hyperosmotic medullary interstitium, which allows the collecting duct to reabsorb water under the influence of antidiuretic hormone. This gradient is essential for producing concentrated urine. Filtration occurs at the glomerulus, and most bicarbonate reabsorption occurs in the proximal tubule.

Question 41Clinical Laboratory Science

Which anticoagulant works by binding calcium ions in the blood collection tube?

  1. Potassium EDTA
  2. Sodium heparin
  3. Sodium citrate Correct answer.
  4. Sodium fluoride

Explanation

Citrate anticoagulants act by chelating calcium, and the effect is reversible, which is why citrate tubes are used for coagulation testing and can be recalcified in the laboratory. The ratio of blood to anticoagulant in citrate tubes must be accurate or results are skewed.

Question 42Clinical Laboratory Science

A blood film shows normocytic, normochromic red cells with marked central pallor and scattered spherocytes after a severe burn. Which finding best explains the spherocytes?

  1. Iron deficiency developing acutely
  2. Hemoglobin C crystallization
  3. Folate deficiency
  4. Membrane loss from thermal injury Correct answer.

Explanation

Thermal injury damages the red cell membrane, causing loss of membrane surface area relative to cell volume, so the cells round up into spherocytes. This is a direct mechanical effect and does not require an immune mechanism.

Question 43Clinical Laboratory Science

In the osmotic fragility test, increased fragility of red cells is most characteristic of which condition?

  1. Sickle cell anemia
  2. Thalassemia trait
  3. Hereditary spherocytosis Correct answer.
  4. Iron deficiency anemia

Explanation

Spherocytes have reduced membrane surface area relative to volume, so they lyse at higher salt concentrations than normal cells, producing increased osmotic fragility. Conditions with thin, flat cells such as thalassemia show decreased fragility.

Question 44Clinical Laboratory Science

Which laboratory finding is most consistent with disseminated intravascular coagulation?

  1. Shortened bleeding time with normal fibrinogen
  2. Elevated fibrinogen with decreased D-dimer
  3. Prolonged PT and aPTT with low fibrinogen and elevated D-dimer Correct answer.
  4. Isolated prolonged aPTT with normal platelet count

Explanation

DIC consumes clotting factors and platelets while activating fibrinolysis, so screening tests show prolonged PT and aPTT, hypofibrinogenemia, thrombocytopenia, and raised fibrin degradation products such as D-dimer. The combination of consumption and fibrinolysis distinguishes it from a single factor deficiency.

Question 45Clinical Laboratory Science

Which parameter is directly measured by a blood gas analyzer rather than calculated?

  1. Base excess
  2. Anion gap
  3. Bicarbonate
  4. pH Correct answer.

Explanation

pH is measured directly with a potentiometric electrode, as are pCO2 and pO2. Bicarbonate, base excess, and the anion gap are derived values computed from measured parameters.

Question 46Clinical Laboratory Science

A patient has a serum calcium of 8.0 mg/dL and an albumin of 2.0 g/dL. Using a correction of 0.8 mg/dL per 1.0 g/dL of albumin below 4.0, what is the albumin-corrected calcium?

  1. 8.8 mg/dL
  2. 9.6 mg/dL Correct answer.
  3. 8.0 mg/dL
  4. 10.4 mg/dL

Explanation

The albumin deficit is 4.0 minus 2.0, or 2.0 g/dL, which is multiplied by 0.8 to give 1.6 mg/dL. Adding this to the measured 8.0 mg/dL yields a corrected value of 9.6 mg/dL.

Question 47Clinical Laboratory Science

Which enzyme is most specific for acute pancreatitis when measured in serum?

  1. Lactate dehydrogenase
  2. Lipase Correct answer.
  3. Alkaline phosphatase
  4. Creatine kinase

Explanation

Lipase is more specific for pancreatic tissue than amylase and remains elevated longer, making it the preferred marker for acute pancreatitis. Its tissue distribution is narrower than that of amylase, which also rises in salivary and other conditions.

Question 48Clinical Laboratory Science

A fasting plasma glucose is 118 mg/dL and a 2-hour oral glucose tolerance value is 152 mg/dL. What is the most appropriate interpretation?

  1. Impaired fasting glucose only
  2. Diabetes mellitus
  3. Normal glucose homeostasis
  4. Impaired glucose tolerance Correct answer.

Explanation

A 2-hour OGTT value between 140 and 199 mg/dL defines impaired glucose tolerance, while the fasting value of 118 mg/dL falls in the impaired fasting glucose range of 100 to 125 mg/dL. Because the 2-hour value is abnormal, the classification is impaired glucose tolerance.

Question 49Clinical Laboratory Science

Which urine finding best distinguishes prerenal azotemia from acute tubular necrosis?

  1. Urine sodium above 40 mmol/L
  2. Urine specific gravity near 1.010
  3. Fractional excretion of sodium below 1 percent Correct answer.
  4. Presence of granular casts

Explanation

In prerenal azotemia the tubules remain functional and avidly reabsorb sodium, giving a low fractional excretion of sodium, typically below 1 percent. In acute tubular necrosis the damaged tubules cannot reabsorb sodium, so the value rises.

Question 50Clinical Laboratory Science

Which organism is most commonly associated with a positive oxidase test and growth on MacConkey agar at 42 degrees Celsius?

  1. Enterococcus faecalis
  2. Escherichia coli
  3. Staphylococcus aureus
  4. Pseudomonas aeruginosa Correct answer.

Explanation

Pseudomonas aeruginosa is oxidase positive, grows readily at 42 degrees Celsius, and can grow on MacConkey agar as a non-lactose fermenter. These features help separate it from enteric organisms and gram-positive cocci.