NEET-PG 2015 Practice Questions

Q: Enzyme deficient in Hers disease -

Liver phosphorylase. ***Liver phosphorylase*** - Hers disease, also known as Glycogen Storage Disease Type VI, is specifically caused by a deficiency of **liver phosphorylase**. - This enzyme is crucial for the breakdown of **glycogen in the liver**, leading to an inability to release glucose into the bloodstream during fasting. *Muscle phosphorylase* - Deficiency of **muscle phosphorylase** (myophosphorylase) causes **McArdle disease** (Glycogen Storage Disease Type V), which primarily affects muscle energy. - Patients typically present with exercise intolerance, muscle pain, and cramps, not the hepatic symptoms seen in Hers disease. *Acid maltase* - Deficiency of **acid maltase** (also known as alpha-glucosidase) is responsible for **Pompe disease** (Glycogen Storage Disease Type II), a lysosomal storage disorder. - This enzyme deficiency leads to glycogen accumulation in lysosomes in various tissues, including muscle, liver, and heart, causing muscle weakness and cardiomyopathy. *Debranching enzyme* - A deficiency in the **debranching enzyme** (amylo-1,6-glucosidase) causes **Cori disease** or **Forbes disease** (Glycogen Storage Disease Type III). - This results in the accumulation of abnormally structured glycogen with short outer branches in the liver, muscle, and heart.

Q: A patient presents with skin involvement and collar stud ulceration in the intestine observed on radiography. What is the most likely diagnosis?

Ulcerative colitis. ***Ulcerative colitis*** - **Collar stud ulcers** are a classic radiographic finding in **ulcerative colitis**, occurring when superficial ulcers undermine the mucosa. - While skin involvement can occur in ulcerative colitis (e.g., **erythema nodosum**, **pyoderma gangrenosum**), the characteristic intestinal ulcers are a strong indicator. *TB intestine* - Intestinal tuberculosis typically presents with **transverse ulcers** and **strictures**, often in the ileocecal region, rather than collar stud ulcers. - Skin involvement is less common and usually manifests as **lupus vulgaris** or **scrofuloderma**, which are distinct from the general "skin involvement" mentioned. *Intestinal Amebiasis* - Amebic colitis causes characteristic **flask-shaped ulcers** in the colon due to the parasite invading the submucosa, which are distinct from collar stud ulcers. - Skin involvement is rare but can occur as **cutaneous amebiasis**, presenting as chronic ulcers, which is not suggested by the general term. *Crohn's disease* - Crohn's disease is characterized by **skip lesions**, **transmural inflammation**, and **cobblestoning**, with deep, linear ulcers and fissures. - While skin manifestations like **erythema nodosum** and **pyoderma gangrenosum** can occur, classical collar stud ulcers are not typical for Crohn's disease.

Q: In the context of immune response, which of the following cell types does not express MHC class II molecules?

NK cells. ***NK cells*** - **Natural Killer (NK) cells)** are innate lymphocytes that do **NOT express MHC class II molecules** under any circumstances. - NK cells use alternative recognition mechanisms (KIRs, activating receptors) to detect target cells, primarily recognizing the **absence of MHC class I** or stress-induced ligands. - They function in innate immunity without antigen presentation capability. - **This is the best answer** as NK cells never express MHC class II, making them distinctly different from professional APCs. *Cortical macrophages* - **Cortical macrophages** in lymphoid organs are professional **antigen-presenting cells (APCs)** that constitutively express **MHC class II molecules**. - They present processed antigens to CD4+ T helper cells, playing a crucial role in initiating adaptive immune responses. *Medullary macrophages* - **Medullary macrophages** are also professional APCs that constitutively express **MHC class II molecules**. - They participate in antigen presentation and immune surveillance within the medullary regions of lymphoid tissues. *Neutrophils* - Neutrophils are granulocytes that **typically do not constitutively express MHC class II molecules** in their resting state. - However, under certain inflammatory conditions with prolonged stimulation (IFN-γ, GM-CSF), neutrophils can be induced to express low levels of MHC class II. - While neutrophils generally lack MHC class II, **NK cells are the more definitive answer** as they never express MHC class II under any physiological or pathological conditions.

Q: Emtricitabine is classified as which of the following?

NRTI. ***NRTI*** - Emtricitabine is a **nucleoside reverse transcriptase inhibitor (NRTI)**, a class of antiretroviral drugs used in the treatment of **HIV infection**. - As an NRTI, it works by inhibiting the enzyme **reverse transcriptase**, which is crucial for the HIV virus to replicate its RNA into DNA. *Alkylating agent* - Alkylating agents are a type of **chemotherapy drug** that kill cancer cells by damaging their DNA. - They are primarily used in **cancer treatment**, not for viral infections like HIV. *Antimetabolite* - Antimetabolites are drugs that interfere with DNA and RNA synthesis, often used in **chemotherapy** to treat cancer or in immunosuppression. - While they can inhibit nucleic acid synthesis, this is a broad category, and emtricitabine's specific mechanism and classification are as an NRTI. *Integrase Inhibitor* - Integrase inhibitors are another class of **antiretroviral drugs** that block the HIV enzyme integrase, preventing the viral DNA from integrating into the host cell's DNA. - While an antiretroviral, emtricitabine has a different mechanism of action and belongs to the NRTI class.

Q: Which of the following is the MOST important factor determining whether a substance can be filtered at the glomerulus?

Molecular weight of the substance. ***Molecular weight of the substance*** - The **glomerular filtration barrier** acts as a size-selective filter, generally permeable to substances with a molecular weight less than 5,000-10,000 Daltons - Larger molecules are typically restricted from filtration due to the **size exclusion** property of the glomerular basement membrane and podocyte slit diaphragms - This is the **primary determinant** of whether a substance can be filtered at all, making it the most important factor among the given options *Lipid solubility of the substance* - **Lipid solubility** is more relevant for reabsorption and secretion in the renal tubules, particularly for passive diffusion across tubular cell membranes - It has minimal direct influence on the initial filtration process at the glomerulus, which is primarily a **pressure-driven, size- and charge-selective ultrafiltration** process - The glomerular capillary wall is not a lipid membrane barrier for the filtration process *Binding capacity to albumin* - Substances bound to **large plasma proteins** like albumin (molecular weight ~67,000 Daltons) cannot pass through the glomerular filtration barrier - While important for determining the *free, filterable fraction* of a substance in plasma, the binding itself is secondary to the fundamental molecular weight/size restriction - Only the **free (unbound) fraction** of a substance is available for filtration, and whether it filters depends primarily on its molecular weight *None of the options* - This option is incorrect because **molecular weight** is indeed the most critical factor among the given options for determining whether a substance can be filtered at the glomerulus

Q: Which of the following cell types is considered insulin-dependent?

Myocytes. ***Myocytes*** - **Myocytes** (skeletal muscle cells) are **insulin-dependent** and represent the **largest site of insulin-mediated glucose disposal** in the body - Insulin promotes translocation of **GLUT4 transporters** to the cell membrane, enabling glucose uptake - Skeletal muscle accounts for approximately **70-80% of postprandial glucose disposal**, making it the most quantitatively significant insulin-dependent tissue *Adipocytes* - **Adipocytes** (fat cells) are also **insulin-dependent** and utilize **GLUT4 transporters** for glucose uptake - Insulin stimulates glucose uptake and conversion to triglycerides for storage - However, adipose tissue accounts for only **10-15% of glucose disposal**, making it less quantitatively significant than skeletal muscle - Both myocytes and adipocytes are considered the two major insulin-dependent tissues in the body *Pituitocytes* - **Pituitocytes** are supporting cells in the pituitary gland - They use **insulin-independent glucose transporters** (GLUT1/GLUT3) - The pituitary gland requires constant glucose supply independent of insulin status *RBCs* - **Red blood cells** lack mitochondria and depend entirely on **anaerobic glycolysis** - Glucose uptake occurs via **insulin-independent GLUT1 transporters** - RBCs must maintain glucose uptake at all times, regardless of insulin levels

Q: Tubuloglomerular feedback is for regulation of?

Renal blood flow. ***Renal blood flow*** - **Tubuloglomerular feedback (TGF)** is a key mechanism that helps to tightly regulate **renal blood flow** and **glomerular filtration rate (GFR)** by sensing tubular fluid composition. - This mechanism involves the **macula densa** cells in the distal tubule sensing changes in **sodium chloride (NaCl) delivery**, which then signals the afferent arteriole to adjust its caliber. *BP* - While renal blood flow ultimately influences **blood pressure (BP)**, tubuloglomerular feedback is primarily focused on **local autoregulation** within the kidney, not systemic BP control. - Systemic BP is regulated by much broader mechanisms involving the **renin-angiotensin-aldosterone system** and **autonomic nervous system**. *Blood volume* - **Blood volume** is primarily regulated by hormones like **ADH (vasopressin)** and **aldosterone**, which influence water and sodium reabsorption in the collecting ducts and other parts of the nephron. - Although renal function impacts blood volume, tubuloglomerular feedback's direct role is not in regulating the overall volume of blood. *Na+ reabsorption* - While the macula densa senses **Na+ delivery** to the distal tubule and this influences GFR, the primary role of tubuloglomerular feedback is not to modulate the total amount of **Na+ reabsorbed** throughout the nephron. - Na+ reabsorption is regulated by multiple factors and occurs extensively in the **proximal tubule**, **loop of Henle**, and **distal tubule**, often under hormonal control.

Q: Which of the following drugs is not used in the treatment of akathisia?

Haloperidol. ***Haloperidol*** - **Haloperidol** is a typical antipsychotic drug known to **cause** or worsen **akathisia**, rather than treat it. - Akathisia is an extrapyramidal symptom, and **first-generation antipsychotics** like haloperidol are frequent culprits due to their strong **D2 receptor blockade**. *Benzodiazepine* - **Benzodiazepines** like lorazepam or clonazepam are often used to treat akathisia due to their **sedative** and **anxiolytic** properties. - They act by enhancing **GABAergic transmission**, which can help calm the motor restlessness associated with akathisia. *Propranolol* - **Propranolol**, a **beta-blocker**, is a first-line treatment for akathisia, particularly effective for its objective motor symptoms. - It works by reducing **adrenergic activity**, which is thought to contribute to the motor restlessness. *Trihexyphenidyl* - **Trihexyphenidyl** is an **anticholinergic** agent primarily used to treat **parkinsonian-like extrapyramidal symptoms** (e.g., dystonia, pseudoparkinsonism). - While sometimes used for generalized EPS, it is **less effective** for the specific motor restlessness of akathisia compared to beta-blockers or benzodiazepines.

Question 1

Enzyme deficient in Hers disease -

Accepted Answer

Liver phosphorylase

Answer

Muscle phosphorylase

Answer

Acid maltase

Answer

Debranching enzyme

Question 2

What is a key similarity between the processes of replication and transcription?

Accepted Answer

Involve phosphodiester bond formation with elongation occurring in the 5' - 3' direction.

Answer

Use RNA primers for initiation.

Answer

Use ribonucleotides as precursors.

Answer

Are semi-conservative events.

Question 3

A patient presents with skin involvement and collar stud ulceration in the intestine observed on radiography. What is the most likely diagnosis?

Accepted Answer

Ulcerative colitis

Answer

TB intestine

Answer

Intestinal Amebiasis

Answer

Crohn's disease

Question 4

In the context of immune response, which of the following cell types does not express MHC class II molecules?

Accepted Answer

NK cells

Answer

Cortical macrophages

Answer

Neutrophils

Answer

Medullary macrophages

Question 5

Which substance plays a significant role in the tumor metastasis cascade?

Accepted Answer

MMP-2 (Matrix Metalloproteinase-2)

Answer

TNF-alpha

Answer

CD99

Answer

NM23

Question 6

Emtricitabine is classified as which of the following?

Accepted Answer

NRTI

Answer

Alkylating agent

Answer

Antimetabolite

Answer

Integrase Inhibitor

Question 7

Which of the following is the MOST important factor determining whether a substance can be filtered at the glomerulus?

Accepted Answer

Molecular weight of the substance

Answer

Lipid solubility of the substance

Answer

Binding capacity to albumin

Answer

None of the options

Question 8

Which of the following cell types is considered insulin-dependent?

Accepted Answer

Myocytes

Answer

Pituitocytes

Answer

Adipocytes

Answer

RBCs

Question 9

Tubuloglomerular feedback is for regulation of?

Accepted Answer

Renal blood flow

Answer

BP

Answer

Blood volume

Answer

Na+ reabsorption

Question 10

Which of the following drugs is not used in the treatment of akathisia?

Accepted Answer

Haloperidol

Answer

Benzodiazepine

Answer

Propranolol

Answer

Trihexyphenidyl

NEET-PG 2015

Biochemistry

Internal Medicine

Microbiology

Pathology

Pharmacology

Physiology

Psychiatry