NEET-PG 2015 Practice Questions

Q: Which of the following is an example of an exopeptidase?

Carboxypeptidases. ***Carboxypeptidases*** - **Carboxypeptidases** are enzymes that cleave the **C-terminal** (carboxyl end) amino acid from a polypeptide chain, making them a type of exopeptidase. - They are crucial in protein digestion, releasing individual amino acids from the end of protein chains. *Trypsin* - **Trypsin** is an **endopeptidase** that cleaves peptide bonds within protein chains, specifically at the carboxyl side of **lysine** or **arginine** residues. - It does not cleave amino acids from the ends of polypeptide chains. *Chymotrypsin* - **Chymotrypsin** is an **endopeptidase** that cleaves peptide bonds within a polypeptide chain, primarily at the carboxyl side of **tyrosine**, **tryptophan**, or **phenylalanine**. - Its action is internal to the protein sequence, not at the termini. *Elastase* - **Elastase** is also an **endopeptidase** that cleaves peptide bonds internally, specifically targeting small, uncharged amino acid residues like **alanine**, **glycine**, and **valine**. - Its primary role is to break down elastin, an elastic protein in connective tissues, but it does so by internal cleavage.

Q: Which of the following is not a part of extracellular matrix (ECM)?

Lectins. ***Lectins*** - **Lectins** are carbohydrate-binding proteins involved in various cellular processes but are typically found **on cell surfaces** or within cells, not as a major structural component of the ECM. - While they can interact with ECM components, they are not considered a direct structural element of the extracellular matrix itself. *Fibronectin* - **Fibronectin** is a critical **glycoprotein** in the ECM, playing a vital role in cell adhesion, growth, migration, and differentiation. - It links cells to collagen fibers and other ECM components, forming an essential scaffold. *Laminin* - **Laminin** is a major **glycoprotein** component of the **basal lamina**, a specialized layer of the ECM found beneath epithelial cells. - It helps in cell attachment, differentiation, and migration. *Proteoglycans* - **Proteoglycans** are macromolecules consisting of a **core protein** covalently linked to one or more **glycosaminoglycan (GAG) chains**. - They are abundant in the ECM, where they contribute to its structural integrity, hydration, and can regulate the diffusion of molecules.

Q: Shrinking Lung Syndrome is seen in:

SLE. ***SLE*** - **Shrinking lung syndrome (SLS)** is a rare but recognized pulmonary manifestation of **systemic lupus erythematosus (SLE)** [1]. - It is characterized by **dyspnea**, **pleuritic chest pain**, and elevated diaphragms with reduced lung volumes, often without significant interstitial lung disease [1]. *Rheumatoid Arthritis* - While **rheumatoid arthritis** can cause various lung manifestations like **interstitial lung disease (ILD)**, pleural effusions, and rheumatoid nodules, **shrinking lung syndrome** is not typically associated with it [2]. - Lung disease in RA often involves **pulmonary fibrosis** or bronchiolitis, differing from the restrictive physiology of SLS. *Scleroderma* - **Scleroderma (Systemic Sclerosis)** commonly affects the lungs, primarily leading to **interstitial lung disease (ILD)** and **pulmonary hypertension** [1]. - **Shrinking lung syndrome**, with its characteristic restrictive pattern and elevated diaphragms, is not a typical presentation of lung involvement in scleroderma. *Sarcoidosis* - **Sarcoidosis** is characterized by the formation of **non-caseating granulomas**, primarily affecting the lungs and lymph nodes. - Lung involvement in sarcoidosis typically presents as **interstitial lung disease** or nodular infiltrates, not the distinct features of **shrinking lung syndrome** [3].

Q: What is the primary effect of beta blockers in the management of thyroid storm?

Provides rapid relief of symptoms. Detailed management of thyrotoxic crisis (thyroid storm) is a medical emergency where patients should be given propranolol, either oral or intravenous, to manage life-threatening symptoms [1]. ***Provides rapid relief of symptoms*** - Beta blockers primarily address the **adrenergic manifestations** of thyroid storm, such as **tachycardia**, **tremors**, anxiety, and palpitations [1]. - By blocking **beta-adrenergic receptors**, they provide rapid symptomatic relief and reduce cardiovascular stress, without affecting hormone levels [2]. Thyroid hormones normally increase the expression of genes for beta-adrenergic receptors and G-proteins, leading to increased heart rate and force of contraction [2]. *Increases metabolism of thyroxine* - Beta blockers do not increase the **metabolism** or breakdown of thyroxine; their action is primarily on the **peripheral effects** of thyroid hormones. - While some beta blockers like **propranolol** can inhibit the peripheral conversion of T4 to T3, this is a secondary effect and not their primary role in providing rapid symptomatic relief [1]. *Blocks thyroxine receptors* - Beta blockers do not block **thyroxine receptors**; thyroid hormones exert their effects by binding to intracellular receptors, not adrenergic receptors [2]. - Their action is on the **adrenergic system**, which is overstimulated by the high levels of thyroid hormones. *Decreases synthesis of thyroxine* - Beta blockers do not directly decrease the **synthesis of thyroxine** by the thyroid gland. - That action is performed by **antithyroid drugs** like methimazole and propylthiouracil, which inhibit hormone production [1].

Q: The process by which antigen-specific B lymphocytes are selected and activated to proliferate and produce antibodies is called:

Clonal selection. ***Clonal selection*** - **Clonal selection** is the fundamental process by which an antigen-specific B lymphocyte is **selected** when its B cell receptor (BCR) recognizes and binds to a matching antigen. - This binding triggers the B cell to become **activated**, **proliferate** (undergo clonal expansion), and **differentiate** into plasma cells that produce antibodies specific to that antigen. - This process is the cornerstone of **adaptive immunity**, ensuring that only B cells with receptors matching the encountered antigen are stimulated to respond. *Class switching* - **Class switching** (isotype switching) occurs AFTER clonal selection and activation. - It allows already-activated B cells to change the **antibody class** they produce (from IgM to IgG, IgA, or IgE) while maintaining the **same antigen specificity**. - This process modifies effector functions but does NOT involve the initial selection and activation of antigen-specific B cells. *Group switching* - This is not a recognized term in immunology. - It does not describe any standard process of B cell activation or antibody production. *Hybridisation* - **Hybridization** refers to the formation of double-stranded nucleic acids from complementary strands or the creation of hybrid cells (e.g., hybridomas for monoclonal antibody production). - It is not the physiological process by which B lymphocytes are selected and activated in response to antigen exposure.

Q: What does ristocetin testing indicate in von Willebrand disease?

Decreased agglutination. ***Decreased agglutination*** - In von Willebrand disease, **ristocetin induces less agglutination** due to a deficiency or dysfunction of von Willebrand factor. - This results in **impaired platelet adhesion** [1], crucial for effective hemostasis. *Increased agglutination* - Would suggest an increased platelet interaction, which is **not characteristic of von Willebrand disease**. - It can occur in conditions with enhanced von Willebrand factor, unlike in this case. *No agglutination* - Suggests complete lack of platelet interaction, which is **not typical** in von Willebrand disease. - There is often some level of interaction, albeit reduced, not a total absence of agglutination. *Normal agglutination* - Indicates no abnormalities, which **contradicts the known pathology** of von Willebrand disease. - Patients typically demonstrate decreased levels of agglutination, not normal findings in this test.

Q: Which antigen is tested in routine Rh typing?

D antigen. ***D antigen*** - Routine Rh typing specifically tests for the **D antigen**, which determines the Rh status of an individual as Rh-positive or Rh-negative [1]. - The presence of the **D antigen** is crucial for blood transfusions and pregnancy management [1]. *A antigen* - The **A antigen** is tested in the context of the ABO blood group system, not specifically for Rh typing. - It does not provide information regarding the Rh factor which is critical in blood compatibility. *C antigen* - Similar to the **A antigen**, the **C antigen** is part of the broader Rh system but is not routinely assessed in standard Rh typing. - Its testing is typically reserved for specific clinical scenarios involving Rh incompatibility. *B antigen* - The **B antigen** pertains to the ABO blood group and does not relate to the Rh factor or routine Rh typing. - Rh typing is solely focused on the **presence of the D antigen** to determine the Rh status. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 627-628.

Q: Flu-like symptoms are a side effect of which anti-TB drug?

Rifampicin. ***Rifampicin*** - **Flu-like syndrome** (fever, chills, myalgia, and headache) is a dose-dependent side effect of **rifampicin**, particularly with intermittent dosing. - This reaction is due to **immunological mechanisms**, involving antibodies against rifampicin. *Isoniazid* - The most significant side effect of isoniazid is **hepatotoxicity**, which can range from mild elevated liver enzymes to severe hepatitis. - It can also cause **peripheral neuropathy**, particularly in malnourished patients or those with risk factors, preventable with pyridoxine (vitamin B6) supplementation. *Pyrazinamide* - **Hepatotoxicity** is a major concern with pyrazinamide, often leading to elevated liver enzymes and, in some cases, severe liver damage. - It frequently causes **hyperuricemia**, which can precipitate acute gouty arthritis due to decreased excretion of uric acid. *Ethambutol* - The most characteristic adverse effect of ethambutol is **optic neuritis**, causing decreased visual acuity, red-green color blindness, and visual field defects. - Regular **ophthalmological monitoring** is crucial during treatment to detect this reversible side effect early.

Q: Antidepressant drug used in nocturnal enuresis is:

Imipramine. ***Imipramine*** - **Imipramine**, a **tricyclic antidepressant (TCA)**, is frequently used off-label for **nocturnal enuresis** in children [1]. - Its mechanism of action in enuresis is thought to involve a combination of anticholinergic effects (which relax the bladder detrusor muscle) and central nervous system effects (which may increase bladder capacity and arousal from sleep) [1]. *Fluoxetine* - **Fluoxetine** is a **selective serotonin reuptake inhibitor (SSRI)** and is primarily used for depression, anxiety disorders, and OCD [2]. - It is not indicated for the treatment of nocturnal enuresis and does not have the same bladder-relaxing or arousal-modulating properties as imipramine in this context. *Trazodone* - **Trazodone** is a **serotonin antagonist and reuptake inhibitor (SARI)**, commonly prescribed for depression and insomnia due to its prominent sedative effects. - It is not used for nocturnal enuresis and its mechanism of action does not confer benefits for bladder control. *Sertraline* - **Sertraline** is another **selective serotonin reuptake inhibitor (SSRI)** used for a wide range of psychiatric conditions, including depression, anxiety, and panic disorder [2]. - Like fluoxetine, it is not an appropriate treatment for nocturnal enuresis and lacks the specific known effects beneficial for this condition.

Q: What is the primary function of the myenteric plexus?

Regulating motility. ***Regulating motility*** - The myenteric plexus, also known as **Auerbach's plexus**, is primarily responsible for coordinating the **rhythmic contractions** and **relaxation of the gastrointestinal (GI) smooth muscle**. - Its strategic location between the **longitudinal and circular muscle layers** allows it to directly influence the strength and frequency of peristalsis, thus regulating the movement of food through the digestive tract. *Regulating GI secretion* - While it has some indirect influence, the **submucosal plexus** (Meissner's plexus) is the primary neural network regulating **secretory functions** of the GI tract. - The myenteric plexus's main role is more directly related to muscle contraction and relaxation rather than glandular secretion. *Regulating local blood flow* - Local blood flow in the GI tract is primarily regulated by the **sympathetic and parasympathetic nervous systems**, along with local metabolic factors and hormones. - The myenteric plexus has a minimal direct role in the control of **GI blood vessel smooth muscle**. *Regulating absorption* - Absorption is primarily a function of the **intestinal epithelial cells** and is regulated by various transport mechanisms, hormones, and local factors. - While the enteric nervous system influences mucosal function indirectly, the myenteric plexus's primary role is **motor control** rather than directly regulating nutrient absorption processes.

Question 1

Which of the following is an example of an exopeptidase?

Accepted Answer

Carboxypeptidases

Answer

Trypsin

Answer

Chymotrypsin

Answer

Elastase

Question 2

Which of the following is not a part of extracellular matrix (ECM)?

Accepted Answer

Lectins

Answer

Fibronectin

Answer

Laminin

Answer

Proteoglycans

Question 3

Shrinking Lung Syndrome is seen in:

Accepted Answer

SLE

Answer

Rheumatoid Arthritis

Answer

Scleroderma

Answer

Sarcoidosis

Question 4

What is the primary effect of beta blockers in the management of thyroid storm?

Accepted Answer

Provides rapid relief of symptoms

Answer

Increases metabolism of thyroxine

Answer

Blocks thyroxine receptors

Answer

Decreases synthesis of thyroxine

Question 5

The process by which antigen-specific B lymphocytes are selected and activated to proliferate and produce antibodies is called:

Accepted Answer

Clonal selection

Answer

Class switching

Answer

Group switching

Answer

Hybridisation

Question 6

What does ristocetin testing indicate in von Willebrand disease?

Accepted Answer

Decreased agglutination

Answer

Normal agglutination

Answer

Increased agglutination

Answer

No agglutination

Question 7

Which antigen is tested in routine Rh typing?

Accepted Answer

D antigen

Answer

C antigen

Answer

A antigen

Answer

B antigen

Question 8

Flu-like symptoms are a side effect of which anti-TB drug?

Accepted Answer

Rifampicin

Answer

Isoniazid

Answer

Pyrazinamide

Answer

Ethambutol

Question 9

Antidepressant drug used in nocturnal enuresis is:

Accepted Answer

Imipramine

Answer

Fluoxetine

Answer

Trazodone

Answer

Sertraline

Question 10

What is the primary function of the myenteric plexus?

Accepted Answer

Regulating motility

Answer

Regulating GI secretion

Answer

Regulating local blood flow

Answer

Regulating absorption

NEET-PG 2015

Biochemistry

Internal Medicine

Microbiology

Pathology

Pharmacology

Physiology