Weekly Pathology Exam - May 15, 2026 (Section A: MCQs)

Question 1

Which blood type is considered the universal donor for red blood cells?

Accepted Answer

AB+ — Type O negative blood lacks both A and B antigens and the Rh factor on the surface of red blood cells, making it compatible with all other blood types.

Question 2

Which blood type is considered the universal recipient for red blood cells?

Accepted Answer

AB+ — Type AB positive blood has both A and B antigens and the Rh factor on red blood cells, so individuals with this blood type can receive red blood cells from all other blood types.

Question 3

What is the main function of plasma in blood transfusions?

Accepted Answer

To provide clotting factors and volume expansion — Fresh frozen plasma (FFP) is transfused to provide clotting factors and to expand blood volume in patients with coagulopathy or massive hemorrhage.

Question 4

Which of the following is a contraindication for blood transfusion?

Accepted Answer

Known hypersensitivity to a specific blood product — A known hypersensitivity reaction to a specific blood product is a contraindication for further transfusion of that product.

Question 5

The term "crossmatch" in blood transfusion refers to:

Accepted Answer

Testing the recipient's plasma for antibodies against donor red blood cells — Crossmatching involves incubating donor red blood cells with recipient serum/plasma to detect any unexpected antibodies that could cause a transfusion reaction.

Question 6

Which of the following is a possible complication of blood transfusion?

Accepted Answer

Pulmonary edema — Transfusion-related acute lung injury (TRALI) and fluid overload can lead to pulmonary edema.

Question 7

Which antigen is present on the surface of red blood cells in Type B blood?

Accepted Answer

A antigen — Type B blood has B antigens on the surface of its red blood cells and anti-A antibodies in its plasma.

Question 8

What is the most important factor in determining blood compatibility between a donor and recipient?

Accepted Answer

ABO and Rh blood groups — ABO and Rh blood group compatibility is paramount to prevent potentially fatal hemolytic transfusion reactions.

Question 9

Which of the following is the primary concern in transfusing Rh-negative blood to an Rh-positive patient?

Accepted Answer

The Rh-negative recipient may develop antibodies against the Rh-positive donor red blood cells. — Transfusing Rh-positive red blood cells to an Rh-negative individual can sensitize them, leading to the production of anti-Rh antibodies, which can cause a reaction in subsequent transfusions or during pregnancy.

Question 10

What is the role of the Rh factor in blood transfusion?

Accepted Answer

It is an antigen on red blood cells that can elicit an immune response. — The Rh factor, specifically the D antigen, is a protein on the surface of red blood cells. If an Rh-negative person is exposed to Rh-positive blood, they can develop antibodies.

Question 11

Which of the following components is typically transfused for patients with low platelet counts?

Accepted Answer

Platelets — Platelet transfusions are administered to individuals with thrombocytopenia (low platelet count) to reduce the risk of bleeding.

Question 12

Which of the following should be monitored during a blood transfusion to detect possible complications?

Accepted Answer

Vital signs (temperature, heart rate, blood pressure) — Monitoring vital signs is crucial during a transfusion to detect early signs of a transfusion reaction, such as fever, chills, hypotension, or tachycardia.

Question 13

What is the normal pH range of human blood?

Accepted Answer

7.35 - 7.45 — The normal arterial blood pH is tightly regulated between 7.35 and 7.45.

Question 14

A patient with chronic obstructive pulmonary disease (COPD) has ABG results showing pH 7.28, PaCO2 58 mmHg, and HCO3- 26 mEq/L. What is the primary acid-base disorder?

Accepted Answer

Respiratory acidosis — The low pH (acidosis) and high PaCO2 (hypercapnia) indicate a primary respiratory acidosis. The HCO3- is slightly elevated, suggesting some metabolic compensation.

Question 15

Which buffer system is the PRIMARY extracellular buffer system in the body?

Accepted Answer

Bicarbonate buffer system — The bicarbonate buffer system (CO2/H2CO3/HCO3-) is the most important extracellular buffer system due to the ability of the respiratory system to regulate CO2 and the kidneys to regulate HCO3-.

Question 16

A diabetic patient presents with rapid, deep breathing (Kussmaul respirations). Which acid-base disorder is this compensatory mechanism addressing?

Accepted Answer

Metabolic acidosis — Kussmaul respirations are a compensatory mechanism to blow off excess CO2 in response to metabolic acidosis, such as diabetic ketoacidosis.

Question 17

What is the normal range for arterial PaCO2?

Accepted Answer

35 - 45 mmHg — The normal partial pressure of carbon dioxide in arterial blood (PaCO2) is 35-45 mmHg.

Question 18

A patient with severe vomiting develops metabolic alkalosis. Which mechanism explains this?

Accepted Answer

Loss of hydrochloric acid (HCl) from the stomach — Vomiting leads to the loss of gastric acid (HCl), which results in an increase in serum bicarbonate and a subsequent metabolic alkalosis.

Question 19

What is the normal range for serum bicarbonate (HCO3-)?

Accepted Answer

22 - 26 mEq/L — The normal serum bicarbonate level is typically between 22 and 26 mEq/L.

Question 20

Which enzyme in renal tubular cells catalyzes the reaction between CO2 and water to form carbonic acid?

Accepted Answer

Carbonic anhydrase — Carbonic anhydrase is a key enzyme in the kidney and other tissues that facilitates the rapid interconversion of carbon dioxide and water to carbonic acid.

Question 21

A patient has ABG results: pH 7.50, PaCO2 30 mmHg, HCO3- 23 mEq/L. What is the diagnosis?

Accepted Answer

Respiratory alkalosis with metabolic compensation — The elevated pH (alkalosis) and low PaCO2 (hypocapnia) indicate a primary respiratory alkalosis. The HCO3- is at the lower end of normal or slightly low, suggesting some metabolic compensation.

Question 22

What is the formula for calculating anion gap?

Accepted Answer

[Na+] - ([Cl-] + [HCO3-]) — The anion gap is calculated as the difference between the measured cations (primarily sodium) and the unmeasured anions (chloride and bicarbonate).

Question 23

Which condition is characterized by an increased anion gap metabolic acidosis?

Accepted Answer

Diabetic ketoacidosis — Diabetic ketoacidosis (DKA) is a classic cause of increased anion gap metabolic acidosis due to the accumulation of ketoacids.

Question 24

A patient at high altitude develops dizziness and tingling in the extremities. Which acid-base disorder is most likely?

Accepted Answer

Respiratory alkalosis — At high altitude, the lower partial pressure of oxygen stimulates hyperventilation, leading to respiratory alkalosis. Symptoms like dizziness and tingling can occur.

Question 25

A patient with von Hippel-Lindau (VHL) syndrome develops multiple tumors. Which molecular mechanism BEST explains the increased angiogenesis in these tumors?

Accepted Answer

Upregulation of VEGF (Vascular Endothelial Growth Factor) — VHL syndrome is associated with defects in the VHL protein, which normally targets HIF-1α for degradation. This leads to increased stabilization and activity of HIF-1α, a transcription factor that upregulates VEGF, a potent stimulator of angiogenesis.

Question 26

A tumor reaches 1.8 mm in diameter but fails to grow further for several years. Which statement BEST explains this phenomenon?

Accepted Answer

The tumor has not yet induced sufficient angiogenesis. — Tumors require a blood supply to grow beyond a few millimeters. Without sufficient angiogenesis, the tumor cannot obtain the oxygen and nutrients necessary for further proliferation.

Question 27

During tumor angiogenesis, MMP-9 performs multiple functions. Which combination of activities is CORRECT?

Accepted Answer

Degradation of basement membrane; release of sequestered growth factors — Matrix metalloproteinase-9 (MMP-9) plays a critical role in breaking down the extracellular matrix and basement membrane, facilitating endothelial cell invasion. It can also release growth factors sequestered in the ECM, further promoting angiogenesis.

Question 28

A researcher studies newly formed tumor vessels and compares them to normal capillaries. Which characteristic would MOST likely be observed in tumor vasculature?

Accepted Answer

Leaky, tortuous vessels with fenestrations — Tumor vasculature is often abnormal, characterized by leaky, tortuous, and dilated vessels with discontinuous basement membranes and fenestrations, which contribute to abnormal blood flow and drug delivery.

Question 29

Normal p53 plays a role in preventing angiogenesis. Which mechanism explains this anti-angiogenic effect?

Accepted Answer

Suppression of genes that inhibit angiogenesis (e.g., TSP-1, AICAR) — The tumor suppressor gene p53 can inhibit angiogenesis by promoting the expression of anti-angiogenic factors like thrombospondin-1 (TSP-1) and by suppressing pro-angiogenic factors like HIF-1α.

Question 30

Three angiogenesis inhibitors—angiostatin, endostatin, and vasculostatin—share what common characteristic?

Accepted Answer

They are all fragments of larger extracellular matrix proteins or basement membrane components. — Angiostatin is a fragment of plasminogen, endostatin is derived from collagen XVIII, and vasculostatin is derived from ectodomain of CD146. They are all degradation products of extracellular matrix or related proteins.

Question 31

Newly formed endothelial cells in tumor vessels contribute to tumor growth through which mechanism BEYOND providing nutrients?

Accepted Answer

Secreting growth factors that promote tumor cell proliferation. — Endothelial cells of tumor vessels are metabolically active and can secrete various growth factors (e.g., EGF, PDGF) that directly stimulate tumor cell growth and survival, in addition to supplying nutrients.

Question 32

A metastatic tumor cell must successfully complete multiple steps to establish a distant metastasis. At which stage do MOST tumor cells fail?

Accepted Answer

Survival and proliferation at a distant site — While invasion and intravasation are challenging, the vast majority of circulating tumor cells fail to survive the hostile microenvironment of the bloodstream or lymphatic system and cannot establish a successful micrometastasis or macrometastasis at a distant site.

Question 33

Loss of E-cadherin function promotes metastasis through which TWO mechanisms?

Accepted Answer

Reduced cell-cell adhesion; increased cell motility — E-cadherin is a key cell adhesion molecule. Loss of E-cadherin leads to decreased cell-cell adhesion, allowing tumor cells to detach and become more motile, facilitating invasion and metastasis.

Question 34

A breast cancer sample shows high expression of CXCR4 and CCR7 chemokine receptors. To which organs is this tumor MOST likely to metastasize?

Accepted Answer

Lymph nodes and lung — CXCR4 is often expressed on tumor cells that metastasize to lymph nodes and the lungs, and CCR7 is a receptor that guides immune cells and tumor cells to lymph nodes. Breast cancer commonly spreads to lymph nodes and then to the lungs.

Question 35

During ECM invasion, tumor cells must complete four sequential steps. Which is the FIRST step?

Accepted Answer

Attachment to extracellular matrix components — The initial step in invasion is for tumor cells to attach to components of the extracellular matrix (ECM), such as laminin or collagen, via specific adhesion molecules.

Question 36

Cleavage of basement membrane collagen IV and laminin by MMPs serves what additional purpose beyond degradation?

Accepted Answer

Release of sequestered growth factors that promote tumor growth — MMPs not only degrade the basement membrane but also release growth factors and cytokines sequestered within the ECM, which can then stimulate tumor cell proliferation, migration, and angiogenesis.

Question 37

Which lipoprotein is responsible for transporting dietary triglycerides from the intestines to tissues?

Accepted Answer

Chylomicrons — Chylomicrons are large lipoprotein particles synthesized in the intestinal cells that transport dietary fats (triglycerides and cholesterol) from the intestine into the lymphatic system and then into the bloodstream for delivery to peripheral tissues.

Question 38

What is the primary function of HDL cholesterol?

Accepted Answer

Transport of cholesterol from peripheral tissues back to the liver — High-density lipoprotein (HDL) cholesterol is known as 'good cholesterol' because it plays a role in reverse cholesterol transport, picking up excess cholesterol from peripheral tissues and returning it to the liver for excretion or reuse.

Question 39

Which enzyme is responsible for breaking down triglycerides in adipose tissue during lipolysis?

Accepted Answer

Hormone-sensitive lipase — Hormone-sensitive lipase (HSL) is the key enzyme in adipose tissue responsible for hydrolyzing stored triglycerides into glycerol and free fatty acids, which are then released into the circulation.

Question 40

What happens to VLDL as it loses triglycerides?

Accepted Answer

It becomes LDL. — Very-low-density lipoprotein (VLDL) particles deliver triglycerides to peripheral tissues. As they lose triglycerides, they undergo a series of transformations, eventually becoming intermediate-density lipoprotein (IDL) and then low-density lipoprotein (LDL).

Question 41

Which hormone promotes lipogenesis and inhibits lipolysis?

Accepted Answer

Insulin — Insulin is a key anabolic hormone that promotes the synthesis of fatty acids and triglycerides (lipogenesis) and inhibits the breakdown of stored fat (lipolysis).

Question 42

What is the genetic defect in familial hypercholesterolemia?

Accepted Answer

Deficiency of LDL receptor — The most common cause of familial hypercholesterolemia is mutations in the gene encoding the LDL receptor, leading to impaired uptake of LDL cholesterol from the bloodstream.

Question 43

Which clinical sign consists of yellowish nodules commonly found on the Achilles tendon in hypercholesterolemia?

Accepted Answer

Xanthomas — Xanthomas are deposits of cholesterol in the skin and tendons. Tendinous xanthomas, particularly on the Achilles tendon, are a hallmark of familial hypercholesterolemia.

Question 44

What condition can severe hypertriglyceridemia lead to?

Accepted Answer

Pancreatitis — Severely elevated triglyceride levels (typically 1000 mg/dL) are a major risk factor for acute pancreatitis.

Question 45

What is lipemia retinalis?

Accepted Answer

Creamy-white appearance of retinal blood vessels due to high triglyceride levels. — Lipemia retinalis is a condition where the retinal blood vessels appear milky white or yellowish due to extremely high levels of triglycerides in the blood.

Question 46

Which statin is commonly used to lower LDL cholesterol?

Accepted Answer

Atorvastatin — Atorvastatin (Lipitor) is a potent HMG-CoA reductase inhibitor (statin) widely prescribed for reducing LDL cholesterol levels.

Question 47

What is the primary metabolic pathway for fatty acid breakdown in mitochondria?

Accepted Answer

Beta-oxidation — Beta-oxidation is the primary process by which fatty acids are broken down into acetyl-CoA molecules within the mitochondrial matrix, providing energy for cellular respiration.

Question 48

Which apolipoprotein defect is responsible for familial dysbetalipoproteinemia?

Accepted Answer

ApoE2 — Familial dysbetalipoproteinemia (Type III hyperlipoproteinemia) is characterized by a defect in apolipoprotein E (specifically the presence of the ApoE2 isoform), which impairs the clearance of chylomicron remnants and VLDL remnants.

Question 49

The primary difference between Quality Control (QC) and Quality Assurance (QA) is:

Accepted Answer

QC focuses on the final product, while QA focuses on the process. — Quality Control (QC) is a set of activities used to ensure that the products or services meet certain standards (e.g., testing control samples). Quality Assurance (QA) is a broader set of activities focused on the entire process to prevent defects and ensure quality from the beginning.

Question 50

Which type of control chart is most commonly used in Internal Quality Control?

Accepted Answer

Levey-Jennings chart — The Levey-Jennings chart is a graphical representation of control data over time, plotting patient results or control values against assigned means and control limits, making it highly effective for internal QC monitoring of laboratory assays.

Weekly Pathology Exam - May 15, 2026 (Section A: MCQs)

Questions, Answers & Explanations