Blood and Immunity Practice Questions

Q: In a Prothrombin Time (PT) test, the addition of Ca2+ and tissue thromboplastin activates which coagulation pathway?

Extrinsic pathway. ### Explanation **1. Why the Extrinsic Pathway is Correct:** The **Prothrombin Time (PT)** test is specifically designed to evaluate the **Extrinsic** and **Common** pathways of coagulation. In this laboratory procedure, **Tissue Thromboplastin (Factor III)** and **Calcium (Factor IV)** are added to the patient's citrated plasma. Tissue thromboplastin directly activates **Factor VII**, bypassing the intrinsic pathway. The Factor VIIa-Tissue Factor complex then activates Factor X, initiating the common pathway to form a fibrin clot. Because the trigger (Tissue Factor) is added from "outside" the blood, it represents the extrinsic mechanism. **2. Why the Incorrect Options are Wrong:** * **Intrinsic Pathway:** This pathway is evaluated by the **Activated Partial Thromboplastin Time (aPTT)** test. It is triggered by "contact activation" involving Factors XII, XI, IX, and VIII. It does not require tissue thromboplastin. * **Common Pathway:** While the PT test *includes* the common pathway (Factors X, V, II, and I), the specific addition of tissue thromboplastin is the defining step for the **activation of the extrinsic pathway**. * **Fibrinolytic Pathway:** This is the process of clot dissolution (mediated by Plasmin), not clot formation. It is assessed by tests like D-dimer or FDP levels. **3. Clinical Pearls for NEET-PG:** * **Warfarin Monitoring:** PT (reported as **INR**) is the gold standard for monitoring Warfarin therapy because Warfarin inhibits Factor VII (which has the shortest half-life). * **Heparin Monitoring:** aPTT is used to monitor Unfractionated Heparin. * **Mnemonic:** **PeT** (PT) is for the **Ex**-girlfriend (Extrinsic); **PiTT** (aPTT) is for the **In**-timate relationship (Intrinsic). * **Vitamin K Dependent Factors:** II, VII, IX, X, Protein C, and Protein S.

Q: Which of the following is NOT a red blood cell membrane protein?

Nebulin. The red blood cell (RBC) membrane is a complex structure composed of a lipid bilayer supported by a specialized protein cytoskeleton that provides the cell with its characteristic biconcave shape and remarkable deformability. **Why Nebulin is the correct answer:** **Nebulin** is a giant protein found exclusively in **skeletal muscle**. It acts as a "molecular ruler" that regulates the length of thin (actin) filaments within the sarcomere. It is not found in the RBC membrane. **Explanation of incorrect options:** * **Spectrin (Option C):** This is the most abundant peripheral membrane protein in RBCs. It forms a flexible hexagonal meshwork that maintains the structural integrity of the cell. * **Ankyrin (Option A):** This is a key "linker" protein. It anchors the spectrin cytoskeleton to the integral membrane protein, Band 3, ensuring the membrane stays attached to the cytoskeleton. * **Glycophorin (Option D):** This is an integral membrane protein. It is rich in sialic acid, which gives the RBC surface a negative charge (zeta potential), preventing cells from sticking to each other and the vessel walls. **High-Yield Clinical Pearls for NEET-PG:** 1. **Hereditary Spherocytosis:** Most commonly caused by a deficiency in **Ankyrin** (most common) or **Spectrin**. This leads to a loss of membrane surface area, resulting in spherical, fragile RBCs. 2. **Hereditary Elliptocytosis:** Primarily caused by defects in **Spectrin** or **Protein 4.1**. 3. **Band 3:** This is the major integral protein that functions as a chloride-bicarbonate exchanger (essential for the Bohr effect and CO2 transport).

Q: Platelet granules contain all of the following, EXCEPT:

ATP. **Explanation:** Platelets contain two primary types of storage granules: **Alpha (α) granules** and **Dense (δ) granules**. Understanding the contents of each is crucial for NEET-PG. **Why ATP is the correct answer:** While ATP is indeed found in platelets, it is specifically localized within the **Dense granules**, not the Alpha granules. The question asks for components of "Platelet granules" in a context where the options A, B, and C are all classic constituents of **Alpha granules**. In many standard physiological classifications (and specifically in the context of this common MCQ), the distinction is made between the protein-rich Alpha granules and the non-protein Dense granules. However, more accurately, ATP is the "odd one out" here because Fibrinogen, Fibronectin, and Factor V are all high-molecular-weight proteins involved in adhesion and coagulation stored in Alpha granules. **Analysis of Incorrect Options:** * **A. Fibrinogen:** A major protein stored in **Alpha granules**. It is essential for platelet aggregation by binding to the GPIIb/IIIa receptor. * **B. Fibronectin:** An adhesive glycoprotein found in **Alpha granules** that aids in platelet attachment to the subendothelial matrix. * **C. Factor V:** Also known as proaccelerin, this clotting factor is synthesized by megakaryocytes and stored in **Alpha granules** to be released upon activation. **High-Yield NEET-PG Pearls:** * **Alpha Granules (Most numerous):** Contain Fibrinogen, vWF, Factor V, Fibronectin, Platelet-Derived Growth Factor (PDGF), and Platelet Factor 4 (PF4). * **Dense Granules (SAC):** Remember the mnemonic **SAC** — **S**erotonin, **A**DP/ATP, and **C**alcium. * **Clinical Correlation:** **Gray Platelet Syndrome** is a rare bleeding disorder caused by a deficiency of Alpha granules. **Storage Pool Deficiency** typically refers to a lack of Dense granules.

Q: What is the important feature of 2,3 diphosphoglycerate?

Higher concentration in adult blood. **Explanation:** **2,3-Diphosphoglycerate (2,3-DPG)** is a metabolic byproduct of glycolysis in red blood cells (Rapoport-Luebering shunt) that acts as a crucial allosteric effector of hemoglobin. 1. **Why Option A is Correct:** Adult hemoglobin (HbA: $\alpha_2\beta_2$) has a high affinity for 2,3-DPG. In contrast, Fetal hemoglobin (HbF: $\alpha_2\gamma_2$) has a low affinity for 2,3-DPG because the $\gamma$-chains lack certain positively charged amino acids (histidine) found in $\beta$-chains. Consequently, **2,3-DPG concentration is significantly higher in adult blood** to regulate oxygen release, whereas its lower binding in fetal blood allows HbF to maintain a higher oxygen affinity for efficient placental transfer. 2. **Why Other Options are Incorrect:** * **Option B:** The **Bohr effect** refers to the shift in the oxygen-hemoglobin dissociation curve caused by changes in **$CO_2$ and $H^+$ (pH)**, not 2,3-DPG. * **Option C:** 2,3-DPG binds to the "T" (Tense) state of hemoglobin, stabilizing it and **decreasing** the affinity for $O_2$. This shifts the curve to the **right**, facilitating $O_2$ unloading to tissues. * **Option D:** While 2,3-DPG is present in the fetus, it is **less effective** in fetal blood. The promotion of oxygenation in the fetus is due to HbF’s *inability* to bind 2,3-DPG effectively, not its association with it. **High-Yield Clinical Pearls for NEET-PG:** * **Right Shift (Increased $O_2$ unloading):** Increased 2,3-DPG, Increased $H^+$ (Acidosis), Increased $CO_2$, Increased Temperature (**Mnemonic: CADET, face Right!**). * **Increased 2,3-DPG levels:** Seen in chronic hypoxia, high altitude, and anemia. * **Blood Storage:** 2,3-DPG levels **decrease** in stored blood; thus, massive transfusions of old blood can cause a left shift, impairing $O_2$ delivery to tissues.

Q: Factor IX is also known as:

Christmas factor. **Explanation:** **Factor IX** is a vitamin K-dependent serine protease in the coagulation cascade. It is known as the **Christmas factor**, named after Stephen Christmas, the first patient diagnosed with its deficiency in 1952. Factor IX is a critical component of the **intrinsic pathway**; it works with its cofactor (Factor VIIIa) to activate Factor X. **Analysis of Options:** * **Option A (Stuart factor):** This refers to **Factor X**. It is the first factor of the **common pathway**, where the intrinsic and extrinsic pathways converge to eventually convert prothrombin to thrombin. * **Option C (Prothrombin):** This is **Factor II**. It is synthesized in the liver and converted into thrombin (IIa) by the prothrombinase complex (Xa, Va, Ca²⁺, and phospholipids). * **Option D (Fibrin factor):** This usually refers to **Factor I (Fibrinogen)**, which is the precursor to fibrin, the meshwork of a blood clot. **Clinical Pearls for NEET-PG:** 1. **Hemophilia B:** Deficiency of Factor IX is called Hemophilia B or **Christmas Disease**. It is an X-linked recessive disorder, clinically indistinguishable from Hemophilia A (Factor VIII deficiency). 2. **Vitamin K Dependence:** Factors **II, VII, IX, and X** (mnemonic: 1972) along with Protein C and S require Vitamin K for γ-carboxylation to become functional. 3. **Laboratory Marker:** Since Factor IX is part of the intrinsic pathway, its deficiency prolongs the **Activated Partial Thromboplastin Time (aPTT)**, while the Prothrombin Time (PT) remains normal.

Q: Albumin exerts high oncotic pressure because?

Low molecular weight and high concentration. **Explanation:** The oncotic pressure (colloid osmotic pressure) of plasma is primarily determined by the **number of particles** in a solution rather than the size of the particles. This is based on Van't Hoff’s Law. **1. Why Option B is Correct:** Albumin accounts for approximately **75-80% of the total plasma oncotic pressure** (about 22 out of 28 mmHg). This is due to two factors: * **High Concentration:** Albumin is the most abundant plasma protein (3.5–5.0 g/dL). Since osmotic pressure is a colligative property, the sheer number of albumin molecules exerts the greatest pull on water. * **Low Molecular Weight:** Compared to other plasma proteins like globulins (MW ~90,000–150,000 Da) or fibrinogen (MW ~340,000 Da), albumin has a relatively **low molecular weight (~69,000 Da)**. For a given mass, a lower molecular weight means more individual molecules are present, further increasing the osmotic effect. **2. Why Other Options are Incorrect:** * **Options A & C:** High molecular weight would mean fewer molecules per unit gram, resulting in *lower* oncotic pressure. * **Options A & D:** Low concentration would significantly decrease the osmotic gradient, leading to fluid leakage into the interstitium (edema). **High-Yield Clinical Pearls for NEET-PG:** * **Gibbs-Donnan Effect:** Albumin is negatively charged at physiological pH. It attracts cations (mainly $Na^+$) into the capillaries, which accounts for about **1/3rd of its total oncotic effect**. * **Hypoalbuminemia:** When serum albumin falls below **2.0–2.5 g/dL** (e.g., in Nephrotic syndrome or Liver Cirrhosis), oncotic pressure drops, leading to generalized edema and ascites. * **Starling’s Forces:** Oncotic pressure is the primary force "holding" fluid inside the vascular compartment, opposing the Hydrostatic pressure which pushes fluid out.

Q: Which interleukin is secreted by Type I helper cells?

Interleukin-2. ### Explanation **Concept Overview:** Helper T-cells (CD4+) differentiate into two primary subsets, **Th1 (Type I)** and **Th2 (Type II)**, based on the cytokines they encounter and subsequently secrete. This distinction is crucial for determining the type of immune response (cellular vs. humoral). **Why Option B is Correct:** **Interleukin-2 (IL-2)** is a signature cytokine of **Th1 cells**. Th1 cells primarily drive **cell-mediated immunity**. They secrete IL-2 (which stimulates T-cell proliferation) and Interferon-gamma (IFN-γ), which activates macrophages and cytotoxic T-cells to fight intracellular pathogens like *M. tuberculosis*. **Analysis of Incorrect Options:** * **Option A (IL-1):** This is a pro-inflammatory cytokine primarily secreted by **macrophages** and antigen-presenting cells (APCs), not Th1 cells. It acts as an endogenous pyrogen. * **Option C (IL-4):** This is the hallmark cytokine of **Th2 cells**. It promotes B-cell differentiation into plasma cells and stimulates the class switching of antibodies to **IgE**. * **Option D (IL-5):** Also secreted by **Th2 cells**, IL-5 is responsible for the proliferation and activation of **eosinophils**, playing a key role in helminthic infections and allergic reactions. **NEET-PG High-Yield Pearls:** * **Th1 Mnemonic:** "1-2-G" (Th**1** secretes IL-**2** and IFN-**G**amma). * **Th2 Mnemonic:** "4, 5, 6, 10, 13" (Th2 cells secrete these interleukins; IL-4 and IL-5 are the most frequently tested). * **The "Switch":** IL-12 induces Th1 differentiation, while IL-4 induces Th2 differentiation. * **Clinical Link:** Lepromatous leprosy involves a Th2 response (ineffective), whereas Tuberculoid leprosy involves a Th1 response (effective clearance).

Q: All of the following are anticoagulants except?

Vascular Endothelial Growth Factor (VEGF). The regulation of hemostasis involves a delicate balance between procoagulant and anticoagulant factors. The question asks to identify the substance that does **not** function as an anticoagulant. **Why VEGF is the correct answer:** **Vascular Endothelial Growth Factor (VEGF)** is primarily a signaling protein that promotes **angiogenesis** (the formation of new blood vessels) and increases vascular permeability. It does not possess intrinsic anticoagulant properties. In fact, in certain pathological states like cancer or chronic inflammation, VEGF can indirectly promote a pro-thrombotic environment by inducing the expression of Tissue Factor. **Analysis of incorrect options:** * **Antithrombin III:** A potent natural anticoagulant that inactivates thrombin (Factor IIa) and Factor Xa [2]. Its activity is significantly enhanced by Heparin. * **Protein S:** Acts as a vital cofactor for **Protein C** [2]. Together, they form a complex that proteolytically inactivates Factors Va and VIIIa, thereby inhibiting the coagulation cascade [2]. * **Nitric Oxide (NO):** Produced by endothelial cells, NO is a potent vasodilator and a strong **inhibitor of platelet aggregation** and adhesion, maintaining the blood in a fluid state [1]. **NEET-PG High-Yield Pearls:** * **Endothelial Anticoagulants:** The healthy endothelium maintains an "anti-thrombotic" surface using Nitric Oxide, Prostacyclin ($PGI_2$), and Thrombomodulin [1]. * **Vitamin K Dependent Factors:** Factors II, VII, IX, X are procoagulants, while **Protein C and S** are anticoagulants; all require Vitamin K for synthesis. * **VEGF Clinical Link:** VEGF inhibitors (e.g., Bevacizumab) are used in oncology and ophthalmology (Wet AMD) but carry a clinical risk of arterial thromboembolism.

Q: All of the following occur in hemostasis except?

Dissolution of clot by plasmin. **Explanation:** Hemostasis is the physiological process that stops bleeding at the site of vascular injury. It is a protective mechanism designed to maintain blood in a fluid state within the vessels while being ready to form a solid plug rapidly upon injury. **Why Option C is the correct answer:** Dissolution of the clot by **plasmin** (Fibrinolysis) is the final stage of the overall process, but it is technically the **termination or reversal of hemostasis**, not a step in its formation. Hemostasis aims to create a clot to prevent blood loss; fibrinolysis occurs later to remove the clot once the vessel wall is repaired and to restore normal blood flow. **Analysis of other options:** * **A. Vasospasm:** This is the immediate **vascular phase** of hemostasis. Myogenic contraction and local autacoid factors (like Thromboxane A2) cause vasoconstriction to reduce blood flow to the injured area. * **B. Platelet plug formation:** Known as **Primary Hemostasis**, this involves platelet adhesion, activation, and aggregation to form a temporary, friable plug. * **D. Formation of fibrin clot:** Known as **Secondary Hemostasis**, this involves the coagulation cascade (intrinsic, extrinsic, and common pathways) which converts soluble fibrinogen into an insoluble fibrin mesh, stabilizing the platelet plug. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Hemostasis:** Vasoconstriction → Primary Hemostasis (Platelet plug) → Secondary Hemostasis (Fibrin clot) → Clot Retraction → Fibrinolysis. * **Plasminogen Activator:** Tissue Plasminogen Activator (tPA) converts plasminogen to plasmin. This is the basis for "clot-buster" therapy in MI and Stroke. * **Vitamin K:** Necessary for the synthesis of factors II, VII, IX, and X. * **Antithrombin III:** The most important natural anticoagulant that inhibits thrombin.

Question 1

In a Prothrombin Time (PT) test, the addition of Ca2+ and tissue thromboplastin activates which coagulation pathway?

Accepted Answer

Extrinsic pathway

Answer

Intrinsic pathway

Answer

Fibrinolytic pathway

Answer

Common pathway

Question 2

Which of the following is NOT a red blood cell membrane protein?

Accepted Answer

Nebulin

Answer

Ankyrin

Answer

Spectrin

Answer

Glycophorin

Question 3

Which of the following statements is true regarding fetal hemoglobin?

Accepted Answer

Hemoglobin A (HbA) first appears in fetal blood at 11 weeks of gestation, coinciding with the initiation of hematopoiesis in the bone marrow.

Answer

Fetal hemoglobin (HbF) binds less avidly to 2,3-diphosphoglycerate (2,3-DPG) compared to adult hemoglobin (HbA).

Answer

HbF is completely replaced by HbA shortly after birth.

Answer

In sickle cell anemia, very low amounts of HbF are produced.

Question 4

Platelet granules contain all of the following, EXCEPT:

Accepted Answer

ATP

Answer

Fibrinogen

Answer

Fibronectin

Answer

Factor V

Question 5

What is the important feature of 2,3 diphosphoglycerate?

Accepted Answer

Higher concentration in adult blood

Answer

Contribution to Bohr effect

Answer

Increased affinity of O2 to haemoglobin

Answer

Associated with foetal blood to promote oxygenation

Question 6

Factor IX is also known as:

Accepted Answer

Christmas factor

Answer

Stuart factor

Answer

Prothrombin

Answer

Fibrin factor

Question 7

Albumin exerts high oncotic pressure because?

Accepted Answer

Low molecular weight and high concentration

Answer

High molecular weight and low concentration

Answer

High molecular weight and high concentration

Answer

Low molecular weight and low concentration

Question 8

Which interleukin is secreted by Type I helper cells?

Accepted Answer

Interleukin-2

Answer

Interleukin-1

Answer

Interleukin-4

Answer

Interleukin-5

Question 9

All of the following are anticoagulants except?

Accepted Answer

Vascular Endothelial Growth Factor (VEGF)

Answer

Antithrombin 3

Answer

Protein S

Answer

Nitric oxide

Question 10

All of the following occur in hemostasis except?

Accepted Answer

Dissolution of clot by plasmin

Answer

Vasospasm of blood vessel

Answer

Platelet plug formation

Answer

Formation of fibrin clot

Blood and Immunity — MCQs

Blood and Immunity — MCQs

On this page

Practice by Chapter

Want unlimited practice?