NEET-PG 2015 Practice Questions

Q: Which type of glial cell is derived from mesodermal origin?

Microglial cells. ***Microglial cells*** - **Microglial cells** are unique among glial cells as they originate from **mesoderm**, specifically from **monocyte/macrophage precursors** in the bone marrow [1]. - They function as the **immune cells of the central nervous system (CNS)**, scavenging for plaques, damaged neurons, and infectious agents [1]. *Macroglial cells* - This is a broad category that includes **astrocytes, oligodendrocytes, and ependymal cells**, all of which are derived from **neuroectoderm**, not mesoderm [1]. - They perform various supportive roles but are distinct in origin from microglial cells [1]. *Oligodendrocytes* - **Oligodendrocytes** are derived from **neuroectoderm** and are responsible for forming the **myelin sheath** around axons in the CNS [2]. - Myelination is crucial for rapid and efficient nerve impulse conduction. *Ependymal cells* - **Ependymal cells** are derived from **neuroectoderm** and line the **ventricles of the brain** and the **central canal of the spinal cord**. - They play a role in the production and circulation of **cerebrospinal fluid (CSF)**.

Q: Which protein does the domain of plasminogen resemble?

Apolipoprotein (a) (a lipoprotein). ***Apolipoprotein (a) (a lipoprotein)*** - **Plasminogen** and **apolipoprotein (a)** share structural homology, specifically due to the presence of **kringle domains**. - This structural similarity suggests a potential for apolipoprotein (a) to **interfere with plasminogen’s fibrinolytic activity**, contributing to **atherosclerosis**. *Fibrinogen (a clotting protein)* - While plasmin acts on fibrinogen (and its derivative fibrin), its domain structure does not **resemble fibrinogen**. - **Fibrinogen** is a large, multi-domain glycoprotein crucial for **clot formation**, distinct from plasminogen's primarily **kringle-rich structure**. *LDL receptor (a lipid metabolism protein)* - The **LDL receptor** is involved in **cholesterol uptake** by cells and has structural features like ligand-binding repeats and epidermal growth factor (EGF) repeats. - Its domain structure is **not similar to plasminogen**, which is characterized by **kringle domains** and a protease domain. *Prothrombin (a coagulation protein)* - **Prothrombin** is a precursor to thrombin, featuring **gla domains**, kringle-like domains (though structurally distinct from plasminogen's), and a serine protease domain. - While both are involved in coagulation/fibrinolysis, their **overall domain arrangements and specific kringle structures differ** significantly.

Q: How many molecules of Acetyl CoA are produced from β-oxidation of palmitic acid?

8 acetyl CoA. ***8 acetyl CoA*** - Palmitic acid is a **16-carbon saturated fatty acid (C16:0)**. During β-oxidation, each cycle cleaves two carbons as **acetyl CoA**. - The formula for acetyl CoA produced is **n/2**, where n = number of carbons. For palmitic acid: 16/2 = **8 acetyl CoA molecules**. - Alternatively: Palmitic acid undergoes **7 cycles of β-oxidation** [(n/2) - 1 = 7], each producing 1 acetyl CoA (7 total), plus the final 2-carbon fragment forming the 8th acetyl CoA. *3 acetyl CoA* - This number is too low for a 16-carbon fatty acid. **Short-chain fatty acids** would produce fewer acetyl CoA molecules. - This value corresponds to β-oxidation of a **6-carbon fatty acid** (hexanoic acid), not palmitic acid. *6 acetyl CoA* - This number is also too low for a 16-carbon fatty acid. - This quantity would be produced from a **12-carbon fatty acid** (lauric acid), not palmitic acid. *16 Acetyl CoA* - This number is too high and would incorrectly imply that each carbon forms an acetyl CoA independently. - Sixteen acetyl CoA molecules would be produced from a **32-carbon fatty acid**, which is extremely rare in biological systems.

Q: What primarily forms the core of chylomicrons?

Triglycerides. ***Triglycerides*** - Chylomicrons are primarily responsible for transporting **dietary triglycerides** from the intestines to other tissues. - Their large core, composed mainly of **triglycerides**, allows efficient transport of these hydrophobic molecules. *Triglycerides and Cholesterol together* - While **cholesterol** is present in chylomicrons, it is less abundant than **triglycerides** and primarily exists as **cholesterol esters** in the core. - The core is not an equal mixture; **triglycerides** overwhelmingly dominate the volume. *Free fatty acids* - **Free fatty acids** are transported in the blood primarily bound to **albumin**, not within the core of chylomicrons. - Chylomicrons typically carry **esterified fatty acids** as part of triglycerides. *Triglyceride, Cholesterol and Phospholipids* - **Phospholipids** form the outer monolayer of the chylomicron, along with apoproteins, making them **amphipathic**. - They do not constitute a core component but rather the **surface interface** with the aqueous environment.

Q: Which of the following is the most reactive free radical?

Hydroxyl radical. ***Hydroxyl radical*** - The **hydroxyl radical (•OH)** is the most reactive free radical in biological systems due to its extremely high oxidation potential and short half-life. - It readily reacts with virtually all cellular macromolecules, including **DNA, proteins, and lipids**, causing widespread damage. *Peroxide radical* - The **peroxide radical (ROO•)**, or more specifically the peroxyl radical, is less reactive than the hydroxyl radical, but still significant in lipid peroxidation. - It plays a role in propagating chain reactions of **lipid damage** in cell membranes. *Alkyl radical* - **Alkyl radicals (R•)** are generally formed as intermediates during the abstraction of hydrogen atoms from saturated compounds. - While reactive, they are typically less reactive and less frequently encountered in biological systems compared to oxygen-centered radicals like the hydroxyl radical. *Superoxide radical* - The **superoxide radical (O₂•−)** is a relatively less reactive free radical compared to the hydroxyl radical, but it is the precursor to many other reactive oxygen species (ROS). - It is primarily involved in **initiation of oxidative stress** and can lead to the formation of more damaging species through reactions like the Haber-Weiss reaction.

Q: Diabetic foot is associated with following type of gangrene -

Wet gangrene. ***Wet gangrene*** - Diabetic foot commonly leads to **ischemia** and **infection** [1], resulting in wet gangrene characterized by moist, necrotic tissue. - This type of gangrene is associated with **rapid progression** and can result in systemic toxicity, making prompt treatment essential. *Fournier's gangrene* - This type of gangrene specifically affects the **perineal** region and is not directly associated with diabetic foot. - It usually arises from infections related to **perineal trauma** or surgical procedures. *Gas gangrene* - Caused by **Clostridium** species and typically follows a traumatic injury or surgical procedure, not specifically related to diabetes. - Presents with **crepitus** and rapid systemic symptoms, different from the chronic nature of diabetic ulcers. *Dry gangrene* - Associated with **chronic ischemia** and necrosis, it occurs in conditions like peripheral arterial disease, not primarily with infections seen in diabetic foot [1]. - It usually develops gradually without the sudden onset of symptoms characteristic of wet gangrene.

Q: First mediator of inflammation to be released is

Histamine. ***Histamine*** - Histamine is the **first mediator of inflammation released** by mast cells and basophils during an allergic or inflammatory response [1][3]. - It promotes **vasodilation** and increased vascular permeability, leading to typical symptoms of inflammation [1][2]. *PAF* - Platelet-activating factor (PAF) is released later in the inflammatory process and is primarily involved in **amplifying** the response rather than initiating it. - It plays a role in **platelet aggregation** and acting on vascular smooth muscle but is not the first released mediator. *Nitric oxide* - Nitric oxide is produced by endothelial cells and plays a role in **vascular relaxation and inflammation**, but it is not among the first mediators released. - It is involved in more **regulatory functions** in the inflammatory response rather than the initial trigger. *IL-1* - Interleukin-1 (IL-1) is a cytokine that is important for the **inflammatory response**, but it is produced after the initial release of mediators like histamine [2]. - It is primarily secreted by **activated macrophages** and contributes to the **amplification** of the immune response [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-94.

Q: Which solid organ is considered to have the lowest risk of rejection during transplantation?

Liver. ***Liver*** - The liver has a unique immunologic environment, often referred to as **immunologic privilege**, which contributes to its lower rates of rejection compared to other transplanted solid organs. - It produces various **immunosuppressive factors** and has a high capacity for regeneration and repair, adapting more readily to the recipient's immune system. - The liver's **dual blood supply** (hepatic artery and portal vein) and tolerogenic properties make it the most immunologically privileged solid organ. *Pancreas* - **Pancreas transplantation** carries a high risk of rejection, with rejection rates significantly higher than liver transplantation. - Pancreatic tissue is highly **immunogenic** due to its endocrine and exocrine functions, requiring aggressive immunosuppression. - Often transplanted with kidney in diabetic patients, and rejection episodes are common. *Kidney* - Kidney transplantation is common, but it carries a significant risk of both **acute and chronic rejection**, requiring lifelong immunosuppression. - The kidney expresses various **MHC antigens** that are readily recognized by the recipient's immune system, making it more immunogenic than the liver. *Heart* - **Heart transplantation** is associated with a high risk of rejection due to the rich vascularity and immunogenicity of cardiac tissue. - It often requires aggressive immunosuppressive regimens to prevent both **acute cellular rejection** and **antibody-mediated rejection**.

Question 1

Which type of glial cell is derived from mesodermal origin?

Accepted Answer

Microglial cells

Answer

Macroglial cells

Answer

Oligodendrocytes

Answer

Ependymal cells

Question 2

Which protein does the domain of plasminogen resemble?

Accepted Answer

Apolipoprotein (a) (a lipoprotein)

Answer

Fibrinogen (a clotting protein)

Answer

LDL receptor (a lipid metabolism protein)

Answer

Prothrombin (a coagulation protein)

Question 3

How many molecules of Acetyl CoA are produced from β-oxidation of palmitic acid?

Accepted Answer

8 acetyl CoA

Answer

3 acetyl CoA

Answer

16 Acetyl CoA

Answer

6 acetyl CoA

Question 4

What primarily forms the core of chylomicrons?

Accepted Answer

Triglycerides

Answer

Triglycerides and Cholesterol together

Answer

Free fatty acids

Answer

Triglyceride, Cholesterol and Phospholipids

Question 5

Which of the following is the most reactive free radical?

Accepted Answer

Hydroxyl radical

Answer

Alkyl radical

Answer

Superoxide radical

Answer

Peroxide radical

Question 6

Which of the following statements about Niemann-Pick disease is false?

Accepted Answer

Type B Niemann-Pick disease is characterized by severe neurological symptoms.

Answer

Due to deficiency of sphingomyelinase.

Answer

CNS symptoms are present in type A.

Answer

Histiocytes show PAS positive inclusions, and Type A is more severe.

Question 7

Diabetic foot is associated with following type of gangrene -

Accepted Answer

Wet gangrene

Answer

Dry gangrene

Answer

Gas gangrene

Answer

Fournier's gangrene

Question 8

Which of the following is not considered an example of excess tissue growth?

Accepted Answer

Granulation tissue

Answer

Neoplasia

Answer

Hyperplasia

Answer

Fibrosis

Question 9

First mediator of inflammation to be released is

Accepted Answer

Histamine

Answer

Nitric oxide

Answer

PAF

Answer

IL-1

Question 10

Which solid organ is considered to have the lowest risk of rejection during transplantation?

Accepted Answer

Liver

Answer

Pancreas

Answer

Kidney

Answer

Heart

NEET-PG 2015

Anatomy

Biochemistry

Pathology

Surgery