Biochemistry
6 questionsCarboxypeptidase contains which mineral?
Which element is required by phosphofructokinase?
In type IA Maple Syrup Urine Disease, which gene mutation is responsible?
What is the major site of protein glycosylation?
What is the normal range of ferritin levels in adult males?
Which of the following is not an acute phase reactant?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 431: Carboxypeptidase contains which mineral?
- A. Copper
- B. Zinc (Correct Answer)
- C. Iron
- D. None of the options
Explanation: ***Zinc*** - **Carboxypeptidase** is a **metalloenzyme**, meaning it requires a metal ion for its catalytic activity. - **Zinc** acts as a crucial cofactor in the active site of carboxypeptidase, enabling its proteolytic function. *Copper* - **Copper** is a component of enzymes like **cytochrome c oxidase** and **superoxide dismutase**, but not carboxypeptidase. - Its presence is essential for processes like **electron transport** and **antioxidant defense**. *Iron* - **Iron** is a central component of **hemoglobin** and **myoglobin** for oxygen transport, and in enzymes like **catalase** and **peroxidase**. - It is not involved in the catalytic mechanism of carboxypeptidase. *None of the options* - This option is incorrect because **Zinc** is a known and essential mineral for the function of carboxypeptidase. - Carboxypeptidase is a metalloenzyme, and a metal cofactor is required for its activity.
Question 432: Which element is required by phosphofructokinase?
- A. Magnesium (Correct Answer)
- B. Inorganic phosphate
- C. Manganese
- D. Copper
Explanation: **Magnesium** - **Phosphofructokinase** (PFK) is an enzyme in **glycolysis** that catalyzes the phosphorylation of fructose-6-phosphate. - This reaction requires **ATP**, and like many enzymes that utilize ATP, PFK requires **magnesium ions (Mg²⁺)** as a cofactor, typically forming a complex with ATP (MgATP²⁻). *Inorganic phosphate* - **Inorganic phosphate** is a substrate for some kinase reactions, but not a direct cofactor requirement for the *activation* of phosphofructokinase itself. - While phosphate is incorporated into molecules during phosphorylation, it does not act as a metal ion cofactor to facilitate the enzyme's activity. *Manganese* - While **manganese (Mn²⁺)** can sometimes substitute for magnesium in certain enzyme reactions, it is not the primary or required cofactor for phosphofructokinase under normal physiological conditions. - Many enzymes have a preference for specific metal ions based on their active site structure and coordination chemistry. *Copper* - **Copper (Cu²⁺)** is a cofactor for a variety of enzymes, particularly those involved in **redox reactions** (e.g., cytochrome c oxidase, superoxide dismutase). - However, copper is not a required metallic cofactor for the activity of **phosphofructokinase** in glycolysis.
Question 433: In type IA Maple Syrup Urine Disease, which gene mutation is responsible?
- A. BCKDHB
- B. DBT
- C. DLD
- D. BCKDHA (Correct Answer)
Explanation: ***BCKDHA*** - **Maple Syrup Urine Disease (MSUD)** type IA is caused by a mutation in the **BCKDHA gene**, which codes for the E1α subunit of the **branched-chain α-keto acid dehydrogenase (BCKD) complex**. - This **enzyme complex** is crucial for the metabolism of **branched-chain amino acids (BCAAs)**: leucine, isoleucine, and valine. *BCKDHB* - The **BCKDHB gene** codes for the E1β subunit of the **BCKD complex**. - Mutations in **BCKDHB** are associated with **type IB MSUD**, not type IA. *DBT* - The **DBT gene** codes for the E2 subunit (dihydrolipoyl transacylase) of the **BCKD complex**. - Mutations in **DBT** are responsible for **type II MSUD**. *DLD* - The **DLD gene** codes for the E3 subunit (dihydrolipoyl dehydrogenase), which is a component shared by several **α-keto acid dehydrogenase complexes**. - Mutations in the **DLD gene** lead to **type III MSUD** and other pyruvate dehydrogenase complex deficiencies, rather than type IA.
Question 434: What is the major site of protein glycosylation?
- A. Ribosome and Golgi body
- B. ER and Ribosome
- C. Ribosome and Cytoplasm
- D. ER and Golgi body (Correct Answer)
Explanation: ***ER and Golgi body*** - The **endoplasmic reticulum (ER)** is the primary site for **N-linked glycosylation**, where carbohydrates are added to the asparagine residues of nascent proteins. - The **Golgi apparatus** is crucial for further modification and processing of these N-linked glycans, as well as the site for **O-linked glycosylation**, where sugars are added to serine or threonine residues. *Ribosome and Golgi body* - **Ribosomes** are responsible for **protein synthesis (translation)** but do not directly perform glycosylation, which is a post-translational modification. - While the **Golgi body** is a site of glycosylation, the ribosome's inclusion makes this option incorrect as the ribosome's role precedes glycosylation. *ER and Ribosome* - The **ER** is a major site of protein glycosylation, especially N-linked glycosylation. - However, **ribosomes** are involved in protein synthesis and lack the enzymatic machinery for adding sugar moieties to proteins. *Ribosome and Cytoplasm* - **Ribosomes** synthesize proteins, but glycosylation does not occur there. - The **cytoplasm** is the site for many metabolic pathways, but major protein glycosylation events mostly occur within the ER and Golgi.
Question 435: What is the normal range of ferritin levels in adult males?
- A. 30-300 ng/ml (Correct Answer)
- B. 300-500 ng/ml
- C. 10-20 ng/ml
- D. 500-700 ng/ml
Explanation: ***30-300 ng/ml*** - The normal range for **ferritin levels** in adult males is typically **30-300 ng/ml** (some laboratories report 30-400 ng/ml). - Ferritin is an **iron storage protein**, and its levels reflect the body's iron stores. - Values below 30 ng/ml suggest **iron deficiency**, while values above 300 ng/ml may indicate iron overload or inflammatory conditions. *10-20 ng/ml* - These levels are **significantly low** and indicate **iron deficiency**. - This range is well below the normal threshold and would warrant investigation and likely iron supplementation. - Levels below 15 ng/ml are diagnostic of **iron deficiency** even in the absence of anemia. *300-500 ng/ml* - Levels in this range are considered **elevated** and can indicate iron overload, chronic inflammation, liver disease, or malignancy. - While some laboratories extend the upper limit to 400 ng/ml, persistent elevation above 300 ng/ml warrants further investigation. - Common causes include **hemochromatosis**, **chronic liver disease**, or **inflammatory conditions**. *500-700 ng/ml* - These levels are **significantly elevated** and strongly suggest **iron overload conditions** such as **hemochromatosis**, severe inflammatory states, or hepatocellular injury. - High ferritin levels can be associated with organ damage, leading to conditions like **cirrhosis** or **cardiomyopathy**. - Requires urgent investigation to identify the underlying cause.
Question 436: Which of the following is not an acute phase reactant?
- A. C-reactive protein
- B. Haptoglobin
- C. Endothelin (Correct Answer)
- D. Fibrinogen
Explanation: ***Endothelin*** - Endothelin is a **vasoconstrictive peptide** primarily involved in regulating **blood vessel tone** and blood pressure. - While it plays a role in processes like inflammation and tissue repair, it is not synthesized or regulated in the same rapid, systemic manner as a classic acute phase reactant. *C-reactive protein* - **C-reactive protein (CRP)** is a rapidly responding acute phase reactant produced by the liver in response to **inflammation**, infection, and tissue injury. - Its levels can rise dramatically within hours of an inflammatory stimulus and are used as a marker for disease activity. *Haptoglobin* - **Haptoglobin** is an acute phase reactant that binds to free **hemoglobin** released from red blood cells during hemolysis, preventing oxidative damage. - Its levels typically increase during acute inflammation or infection, although it can also decrease with severe hemolysis. *Fibrinogen* - **Fibrinogen** is a critical acute phase protein involved in the **coagulation cascade** and wound healing. - Its concentration increases significantly during acute inflammation, contributing to the elevated **erythrocyte sedimentation rate (ESR)**.
Microbiology
2 questionsJSB stain is used for which parasite?
Which of the following amoebae does not have a neuropathogenic effect?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 431: JSB stain is used for which parasite?
- A. Kala azar
- B. Sleeping sickness
- C. Malaria
- D. Filaria (Correct Answer)
Explanation: ***Filaria*** - The **JSB stain (Jaswant Singh Battacharya stain)** is a rapid Romanowsky-type stain specifically developed for the diagnosis of **microfilariae** in blood films. - It allows for clear visualization of the sheaths and nuclei of microfilariae, which is crucial for species identification and diagnosis of **filariasis**. *Malaria* - **Giemsa stain** is the gold standard for identifying malaria parasites in thick and thin blood smears, not JSB stain. - Giemsa allows for detailed morphological differentiation of malaria species and stages within **red blood cells**. *Kala azar* - **Kala-azar (visceral leishmaniasis)** is diagnosed by detecting **Leishman bodies (amastigotes)** in bone marrow, splenic, or lymph node aspirates. - Stains like **Giemsa** or **Leishman stain** are traditionally used for visualizing these amastigotes. *Sleeping sickness* - **Sleeping sickness (African trypanosomiasis)** is diagnosed by identifying **trypomastigotes** in blood smears, lymph node aspirates, or cerebrospinal fluid. - **Giemsa stain** is commonly used for the microscopic examination of these specimens to detect the parasites.
Question 432: Which of the following amoebae does not have a neuropathogenic effect?
- A. Naegleria
- B. Acanthamoeba
- C. Dientamoeba (Correct Answer)
- D. Balamuthia
Explanation: ***Dientamoeba*** - *Dientamoeba fragilis* is an intestinal flagellate (often mistakenly classified as an amoeba) that causes **gastrointestinal symptoms** like diarrhea and abdominal pain. - It has **no known neuropathogenic effects** and does not invade the central nervous system. *Naegleria* - *Naegleria fowleri* is a highly virulent amoeba that causes **primary amoebic meningoencephalitis (PAM)**, a rapidly fatal infection of the central nervous system. - It typically invades the brain after **nasal insufflation** of contaminated water. *Acanthamoeba* - *Acanthamoeba* species can cause **granulomatous amoebic encephalitis (GAE)**, a subacute to chronic central nervous system infection, particularly in immunocompromised individuals. - They are also known to cause **amoebic keratitis**, a severe eye infection. *Balamuthia* - *Balamuthia mandrillaris* causes **granulomatous amoebic encephalitis (GAE)**, similar to *Acanthamoeba*, but often in both immunocompetent and immunocompromised individuals. - It can also lead to **skin lesions** and has a tropism for the brain, causing severe neurological damage.
Pharmacology
1 questionsWhich of the following is not an ionic receptor?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 431: Which of the following is not an ionic receptor?
- A. Kainate
- B. AMPA
- C. mGluR (Correct Answer)
- D. NMDA
Explanation: **Ionic receptors** (ionotropic receptors) are ligand-gated ion channels that open upon binding, allowing ions to flow directly through the channel. **Non-ionic receptors** (metabotropic receptors) are G-protein coupled receptors that activate intracellular signaling cascades. ***mGluR*** - **Metabotropic glutamate receptors (mGluRs)** are **G-protein coupled receptors** (GPCRs), meaning they activate intracellular signaling pathways rather than directly forming an ion channel. - Their activation leads to slower, longer-lasting changes in neuronal excitability through second messenger systems. - **This is the correct answer** as mGluRs are NOT ionic receptors. *NMDA* - **NMDA receptors** are **ionotropic glutamate receptors** that form ligand-gated ion channels permeable to calcium and sodium ions. - They are crucial for **synaptic plasticity** and learning. *Kainate* - **Kainate receptors** are also **ionotropic glutamate receptors** that are permeable to sodium and potassium ions. - They play diverse roles in synaptic transmission and neuronal excitability. *AMPA* - **AMPA receptors** are **ionotropic glutamate receptors** primarily responsible for fast excitatory synaptic transmission in the central nervous system. - They are permeable to sodium and potassium ions and mediate the majority of fast excitatory synaptic currents.
Physiology
1 questionsATPase activity is present in
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 431: ATPase activity is present in
- A. Myosin (Correct Answer)
- B. Actin
- C. Actin during interaction with myosin
- D. None of the options
Explanation: ***Myosin*** - Myosin heads possess intrinsic **ATPase activity**, meaning they can hydrolyze ATP into ADP and inorganic phosphate. - This **ATP hydrolysis** provides the energy required for the **power stroke** during muscle contraction, detaching the myosin head from actin. *Actin* - Actin filaments themselves do not have ATPase activity. - Actin's primary role is to form the **thin filaments** and bind to myosin heads during contraction. *Actin during interaction with myosin* - While actin interacts with myosin, it does not acquire ATPase activity. - The **myosin head**, not actin, is responsible for ATP hydrolysis during this interaction. *None of the options* - This option is incorrect because **myosin** clearly possesses ATPase activity, which is crucial for muscle function.