Blood and Immunity Practice Questions

Q: Blood group antigens are chemically:

Glycoprotein. ### Explanation **Correct Answer: B. Glycoprotein** **Why Glycoprotein is Correct:** Blood group antigens (such as ABO and Rh) are biochemical markers located on the surface of the erythrocyte membrane. While the **antigenic specificity** (the part that determines the blood type) is often determined by specific sugar sequences (carbohydrates), the **entire chemical structure** of the antigen molecule anchored to the red cell membrane is a **glycoprotein** or a **glycolipid**. In the context of standard medical examinations like NEET-PG, these antigens are primarily classified as glycoproteins because they consist of a polypeptide backbone with attached oligosaccharide chains. **Analysis of Incorrect Options:** * **A. Carbohydrate:** While the terminal sugars (e.g., N-acetylgalactosamine for Group A, Galactose for Group B) define the immunological specificity, the carbohydrate does not exist in isolation; it is attached to a protein or lipid base. * **C. Phospholipids:** These form the structural bilayer of the cell membrane but do not function as the primary ABO or Rh antigens. * **D. Polysaccharide:** This term refers to long chains of monosaccharides. While the antigenic portion is an oligosaccharide, the molecule as a whole is a conjugated protein. **High-Yield Clinical Pearls for NEET-PG:** * **ABO Antigens:** These are found not only on RBCs but also in most body fluids (if the person is a "secretor"). They are primarily **Glycoproteins** in secretions and **Glycolipids/Glycoproteins** on RBC membranes. * **Rh Antigen:** Unlike ABO, the Rh antigen is a **pure protein** (non-glycosylated) and is found exclusively on the RBC membrane. * **H-Antigen:** This is the precursor molecule. The *H gene* codes for **Fucosyltransferase**, which adds L-fucose to the precursor chain. * **Bombay Blood Group:** Characterized by the absence of the H-antigen (genotype *hh*). These individuals produce anti-H antibodies.

Q: Erythropoiesis in the fetal liver begins during which period?

6-8 weeks. ### Explanation The correct answer is **6-8 weeks**. Erythropoiesis (the production of red blood cells) in the fetus occurs in distinct stages, transitioning through different anatomical sites as development progresses. **1. Why 6-8 weeks is correct:** Fetal erythropoiesis is divided into three stages: * **Mesoblastic Stage:** Starts at ~3 weeks in the yolk sac. * **Hepatic Stage:** The liver becomes the primary site of hematopoiesis starting around **6-8 weeks** of gestation. It reaches its peak activity at 3-4 months and continues until shortly before birth. * **Myeloid Stage:** The bone marrow takes over as the primary site starting from the 5th month (20 weeks). **2. Analysis of Incorrect Options:** * **2-4 weeks:** This corresponds to the **Mesoblastic stage**, where erythropoiesis occurs in the yolk sac (specifically the blood islands). The liver has not yet developed hematopoietic function. * **4-6 weeks:** This is a transitional period. While the liver primordium is forming, active erythropoiesis typically establishes firmly between the 6th and 8th week. * **8-10 weeks:** By this time, hepatic erythropoiesis is already well-established. This option is too late for the *onset* of the hepatic stage. **3. NEET-PG High-Yield Facts (Clinical Pearls):** * **Mnemonic for sites:** **"Young Liver Synthesizes Blood"** (Yolk sac → Liver → Spleen → Bone marrow). * **Spleen involvement:** The spleen contributes to erythropoiesis between the 10th and 28th weeks. * **Fetal Hemoglobin (HbF):** The hepatic stage is primarily associated with the production of HbF ($\alpha_2\gamma_2$), which has a higher affinity for oxygen than adult hemoglobin (HbA). * **Post-natal site:** In adults, the liver only resumes erythropoiesis in pathological states (Extramedullary Hematopoiesis), such as Myelofibrosis or Thalassemia.

Q: Coagulation process starts with the help of all except?

Phospholipids. ### Explanation The coagulation cascade is initiated via two pathways: the **Extrinsic pathway** (triggered by Tissue Factor) and the **Intrinsic pathway** (triggered by contact activation). **1. Why Phospholipids is the Correct Answer:** While phospholipids (specifically Platelet Factor 3) are **essential co-factors** required for the formation of the Tenase and Prothrombinase complexes later in the cascade, they do not **start** (initiate) the process. Coagulation is initiated by the activation of Factor XII (in the intrinsic pathway) or Factor VII (in the extrinsic pathway). Phospholipids provide the surface upon which these activated factors interact, but they are not the primary triggers. **2. Analysis of Incorrect Options:** * **Hageman Factor (Factor XII):** This is the primary initiator of the **Intrinsic Pathway**. When it comes into contact with negatively charged surfaces (like collagen or glass), it undergoes a conformational change to become XIIa. * **Kallikrein & HMW Kininogen (HMWK):** These are part of the **"Contact Activation System."** HMWK acts as a cofactor that anchors Factor XII and Prekallikrein to the subendothelial surface. Kallikrein further activates Factor XII via a positive feedback loop. Together with Factor XII, they are the starting components of the intrinsic cascade. ### Clinical Pearls for NEET-PG: * **Contact Activation:** The trio of Factor XII, HMWK, and Prekallikrein initiates the intrinsic pathway *in vitro* (e.g., in a test tube). * **In Vivo Initiation:** In the human body, the **Extrinsic Pathway** (Factor VII + Tissue Factor) is the most important initiator of coagulation. * **Factor XII Deficiency:** Interestingly, patients with Factor XII deficiency show a prolonged aPTT in the lab but **do not** have clinical bleeding tendencies. * **Vitamin K Dependent Factors:** II, VII, IX, X, Protein C, and Protein S.

Q: In the coagulation cascade, the clot is initiated by negatively charged particles on a glass bead. How is it initiated in vivo?

Tissue factor. **Explanation:** The coagulation cascade is divided into two pathways that converge into a common pathway. 1. **The Correct Answer (A):** In an *in vitro* setting (like a glass tube), the **Intrinsic Pathway** is triggered by contact with negatively charged surfaces (Factor XII). However, **in vivo**, the primary initiator of coagulation is the **Extrinsic Pathway**. This is triggered by **Tissue Factor (Factor III/Thromboplastin)**, which is released from damaged subendothelial cells. Tissue Factor binds with Factor VIIa to form a complex that activates Factor X, leading to the "thrombin burst" necessary for stable clot formation. 2. **Why other options are incorrect:** * **B. Thrombin (Factor IIa):** Thrombin is the *product* of the coagulation cascade, not the initiator. While it provides positive feedback to amplify the cascade, it is not the trigger for the initial clot. * **C. Endothelin:** This is a potent vasoconstrictor released by damaged endothelium. It helps reduce blood flow to the site of injury but does not initiate the chemical coagulation cascade. * **D. von Willebrand factor (vWF):** vWF is crucial for **primary hemostasis** (platelet adhesion to subendothelial collagen). It does not initiate the secondary hemostasis (coagulation cascade), though it does stabilize Factor VIII in the blood. **High-Yield NEET-PG Pearls:** * **Rate-limiting step:** The activation of Factor X (where intrinsic and extrinsic pathways meet). * **Vitamin K dependent factors:** II, VII, IX, X, Protein C, and Protein S. * **Shortest half-life:** Factor VII (this is why PT/INR is used to monitor early liver failure or warfarin therapy). * **Calcium (Factor IV):** Required for almost all steps of the cascade except the initial steps of the intrinsic pathway.

Q: An increase in the concentration of 2,3-Biphosphoglycerate (2,3-DPG) may be seen in all of the following conditions EXCEPT?

Hypoxanthine. **Explanation:** The concentration of **2,3-Bisphosphoglycerate (2,3-BPG/DPG)** in red blood cells is a critical regulator of hemoglobin’s affinity for oxygen. An increase in 2,3-BPG shifts the oxygen-dissociation curve to the **right**, facilitating oxygen unloading to tissues. **Why Hypoxanthine is the Correct Answer:** Hypoxanthine is a breakdown product of purine metabolism and does not directly stimulate the glycolytic pathway (Rapoport-Luebering shunt) responsible for 2,3-BPG production. Unlike Inosine, Hypoxanthine cannot be effectively utilized by the RBC to regenerate ATP or 2,3-BPG. **Analysis of Other Options:** * **Anemia:** In chronic anemia, the body compensates for reduced hemoglobin levels by increasing 2,3-BPG levels to enhance oxygen delivery to peripheral tissues. * **Hypoxia:** Low arterial oxygen (e.g., at high altitudes or in chronic obstructive pulmonary disease) triggers an adaptive increase in 2,3-BPG to optimize tissue oxygenation. * **Inosine:** In blood banking, Inosine is added to storage media because it can be converted into ribose-5-phosphate, which enters the glycolytic pathway, thereby **increasing** 2,3-BPG levels in stored blood. **High-Yield Clinical Pearls for NEET-PG:** * **Rapoport-Luebering Shunt:** The specific pathway in RBCs that produces 2,3-BPG. * **Right Shift Factors:** "CADET, face Right!" (**C**O2, **A**cid/H+, 2,3-**D**PG, **E**xercise, **T**emperature). * **Fetal Hemoglobin (HbF):** Has a lower affinity for 2,3-BPG compared to HbA, resulting in a **left shift** (higher O2 affinity), which allows the fetus to pull oxygen from maternal blood. * **Stored Blood:** 2,3-BPG levels drop during storage; massive transfusions of old blood can cause a left shift, potentially impairing tissue oxygenation.

Q: Which of the following types of white blood cells are most numerous in human blood?

Neutrophils. **Explanation:** In human physiology, white blood cells (leukocytes) are categorized based on their prevalence and morphology. **Neutrophils** are the most abundant type of leukocyte, typically accounting for **40% to 70%** of the total white blood cell count in a healthy adult. They serve as the primary "first responders" of the innate immune system, migrating rapidly to sites of acute bacterial infection to perform phagocytosis. **Analysis of Options:** * **Neutrophils (Correct):** As the most numerous cell type, they are essential for acute inflammatory responses. Their count increases significantly during bacterial infections (Neutrophilia). * **Eosinophils (Incorrect):** These make up only **1% to 4%** of total WBCs. They are primarily involved in combating parasitic infections and mediating allergic reactions. * **Basophils (Incorrect):** These are the least common leukocytes, comprising **0.5% to 1%** of the total count. They contain histamine and heparin, playing a role in immediate hypersensitivity reactions. * **Monocytes (Incorrect):** These constitute **2% to 8%** of WBCs. They are the largest leukocytes and eventually migrate into tissues to become macrophages. **High-Yield NEET-PG Pearls:** 1. **Mnemonic for WBC Prevalence:** **N**ever **L**et **M**onkeys **E**at **B**ananas (**N**eutrophils > **L**ymphocytes > **M**onocytes > **E**osinophils > **B**asophils). 2. **Absolute Neutrophil Count (ANC):** A value below 1,500 cells/mm³ is defined as Neutropenia, which significantly increases the risk of life-threatening infections. 3. **Shift to the Left:** This clinical term refers to an increase in immature neutrophils (band cells) in the blood, usually indicating an active acute infection.

Q: Alpha granules of platelets contain all of the following except?

ADP. **Explanation:** Platelets contain two main types of secretory granules: **Alpha ($\alpha$) granules** and **Dense ($\delta$) granules**. Distinguishing between their contents is a high-yield topic for NEET-PG. **Why ADP is the correct answer:** **ADP (Adenosine Diphosphate)** is stored in the **Dense granules**, not alpha granules. Dense granules are smaller and contain non-protein substances essential for platelet activation and vasoconstriction, often remembered by the mnemonic **SAC** (Serotonin, ADP/ATP, and Calcium). ADP specifically plays a crucial role in recruiting more platelets to the site of injury by binding to P2Y1 and P2Y12 receptors. **Analysis of incorrect options:** * **A. Fibrinogen:** This is a major protein component of **Alpha granules**. It is essential for platelet aggregation as it forms bridges between GP IIb/IIIa receptors. * **B & C. TGF-beta and PDGF:** Alpha granules are the primary storage site for various growth factors, including **Transforming Growth Factor-beta (TGF-$\beta$)**, **Platelet-Derived Growth Factor (PDGF)**, and Vascular Endothelial Growth Factor (VEGF). These are vital for wound healing and tissue repair. **High-Yield Clinical Pearls:** * **Alpha Granules (Most numerous):** Contain high-molecular-weight proteins like vWF, Factor V, Fibrinogen, Fibronectin, and Platelet Factor 4 (PF4). * **Dense Granules (Fewer):** Contain "Small molecules" – ADP, ATP, Serotonin (5-HT), Calcium, and Pyrophosphate. * **Gray Platelet Syndrome:** A rare bleeding disorder caused by a congenital deficiency of **Alpha granules**. * **Hermansky-Pudlak Syndrome:** Associated with a deficiency of **Dense granules** (presents with albinism and bleeding diathesis).

Q: Plasma is the fluid portion of the blood which aids in the transport of other substances in the body. Total plasma volume in relation to body weight is:

5%. ### Explanation The correct answer is **A. 5%**. **1. Understanding the Medical Concept:** Total Body Water (TBW) constitutes approximately **60%** of the total body weight in an average adult male. This water is distributed into two main compartments: * **Intracellular Fluid (ICF):** 40% of body weight (2/3 of TBW). * **Extracellular Fluid (ECF):** 20% of body weight (1/3 of TBW). The ECF is further divided into **Interstitial Fluid (15%)** and **Plasma (5%)**. Therefore, plasma volume—the liquid component of blood—represents approximately 5% of the total body weight (e.g., in a 70 kg man, plasma volume is ~3.5 liters). **2. Analysis of Incorrect Options:** * **B. 10%:** This value does not correspond to a major fluid compartment. However, total blood volume (plasma + cells) is roughly 7–8% of body weight. * **C. 20%:** This represents the **Total Extracellular Fluid (ECF)** volume, which includes both plasma and the fluid bathing the cells (interstitial fluid). * **D. 25%:** This value is higher than the total ECF and does not align with standard physiological fluid distribution. **3. NEET-PG High-Yield Pearls:** * **Blood Volume vs. Plasma Volume:** Remember that Blood Volume = Plasma Volume / (1 – Hematocrit). Total blood volume is ~8% of body weight. * **Measurement:** Plasma volume is most commonly measured using **Evans Blue dye (T-1824)** or **Radioiodinated Albumin (I-131)** because these substances bind to albumin and remain within the vascular compartment. * **Indicator Dilution Principle:** The formula used for these calculations is $Volume = \frac{Amount\ of\ Tracer}{Concentration}$. * **Hematocrit (Hct):** The percentage of blood volume occupied by RBCs, normally ~45%.

Question 1

Blood group antigens are chemically:

Accepted Answer

Glycoprotein

Answer

Carbohydrate

Answer

Phospholipids

Answer

Polysaccharide

Question 2

Erythropoiesis in the fetal liver begins during which period?

Accepted Answer

6-8 weeks

Answer

2-4 weeks

Answer

4-6 weeks

Answer

8-10 weeks

Question 3

Coagulation process starts with the help of all except?

Accepted Answer

Phospholipids

Answer

Kalleikrein

Answer

Hageman factor

Answer

HMW kininogen

Question 4

Which of the following is NOT exclusively produced by the liver?

Accepted Answer

Globulin

Answer

Factor VII

Answer

Prothrombin

Answer

Albumin

Question 5

In the coagulation cascade, the clot is initiated by negatively charged particles on a glass bead. How is it initiated in vivo?

Accepted Answer

Tissue factor

Answer

Thrombin

Answer

Endothelin

Answer

von Willebrand factor

Question 6

Which of the following is not a platelet-associated coagulation factor?

Accepted Answer

Factor IX

Answer

von Willebrand factor (vWF)

Answer

Factor XI

Answer

Factor XIII

Question 7

An increase in the concentration of 2,3-Biphosphoglycerate (2,3-DPG) may be seen in all of the following conditions EXCEPT?

Accepted Answer

Hypoxanthine

Answer

Anemia

Answer

Hypoxia

Answer

Inosine

Question 8

Which of the following types of white blood cells are most numerous in human blood?

Accepted Answer

Neutrophils

Answer

Eosinophils

Answer

Basophils

Answer

Monocytes

Question 9

Alpha granules of platelets contain all of the following except?

Accepted Answer

ADP

Answer

Fibrinogen

Answer

TGF-beta

Answer

PDGF

Question 10

Plasma is the fluid portion of the blood which aids in the transport of other substances in the body. Total plasma volume in relation to body weight is:

Accepted Answer

5%

Answer

10%

Answer

20%

Answer

25%

Blood and Immunity — MCQs

Blood and Immunity — MCQs

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