Biochemistry
3 questionsWhich of the following enzymes is classified as a serine protease?
Which protein hormone is often referred to as the 'guardian angel against obesity' due to its role in regulating metabolism?
Which of the following is an aldose?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 351: Which of the following enzymes is classified as a serine protease?
- A. Pepsin
- B. Trypsin (Correct Answer)
- C. Carboxypeptidase
- D. None of the options
Explanation: ***Trypsin*** - **Trypsin** is a digestive enzyme belonging to the **serine protease** family, characterized by a crucial **serine residue** in its active site. - It plays a vital role in protein digestion in the small intestine, cleaving peptide bonds on the carboxyl side of **lysine** or **arginine** residues. *Pepsin* - **Pepsin** is an aspartic protease, meaning it utilizes an **aspartate residue** in its active site for catalysis. - It primarily functions in the stomach, digesting proteins into smaller peptides in an **acidic environment**. *Carboxypeptidase* - **Carboxypeptidase** is a **metalloexopeptidase** that contains a zinc ion in its active site. - It removes amino acids one by one from the **carboxyl-terminal** end of polypeptide chains. *None of the options* - This option is incorrect because **trypsin** is indeed a well-known example of a serine protease.
Question 352: Which protein hormone is often referred to as the 'guardian angel against obesity' due to its role in regulating metabolism?
- A. Adiponectin (Correct Answer)
- B. Fibronectin
- C. High-Density Lipoprotein (HDL)
- D. Insulin
Explanation: ***Adiponectin*** - **Adiponectin** is a hormone secreted by **adipose tissue** that plays a crucial role in regulating glucose and fatty acid metabolism, increasing **insulin sensitivity**, and decreasing inflammation. - Its levels are inversely correlated with body fat percentage; individuals with obesity tend to have lower adiponectin levels, leading to its nickname as the 'guardian angel against obesity'. *Fibronectin* - **Fibronectin** is a glycoprotein involved in cell adhesion, growth, migration, and differentiation, and is a key component of the **extracellular matrix**. - It does not primarily function in metabolic regulation or body weight control, unlike adiponectin. *High-Density Lipoprotein (HDL)* - **HDL** is a type of lipoprotein that transports cholesterol from peripheral tissues back to the liver, a process known as **reverse cholesterol transport**. - While beneficial for cardiovascular health, HDL is a lipid-carrying particle, not a protein hormone, and its primary role is not in metabolic regulation or direct obesity prevention. *Insulin* - **Insulin** is a peptide hormone produced by the pancreas that regulates carbohydrate and fat metabolism, primarily by facilitating glucose uptake from the blood into cells. - While essential for metabolism, high levels of insulin in the context of insulin resistance can contribute to obesity, rather than act against it.
Question 353: Which of the following is an aldose?
- A. Fructose
- B. Erythrulose
- C. Glucose (Correct Answer)
- D. None of the options
Explanation: ***Glucose*** - An **aldose** is a monosaccharide containing an **aldehyde group** (—CHO) in its open-chain form. - **Glucose** possesses an aldehyde group at carbon-1 and is therefore classified as an aldose. *Fructose* - **Fructose** is a **ketose**, meaning it contains a **ketone group** (C=O) in its open-chain structure, typically at carbon-2. - While it is a monosaccharide, its functional group differentiates it from aldoses. *Erythrulose* - **Erythrulose** is a **ketotetrose**, meaning it is a four-carbon sugar with a **ketone group**. - Unlike aldoses, which have an aldehyde group, erythrulose's defining characteristic is its ketone functional group. *None of the options* - This option is incorrect because **Glucose** is indeed an aldose, fitting the definition of having an aldehyde functional group. - Therefore, there is a correct option provided among the choices.
Internal Medicine
2 questionsWhich of the following does not synthesize von Willebrand factor?
Type 3 respiratory failure occurs due to ?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 351: Which of the following does not synthesize von Willebrand factor?
- A. Endothelial cells
- B. Hepatocytes (Correct Answer)
- C. Megakaryocytes
- D. None of the options
Explanation: ***Hepatocytes*** - Von Willebrand factor (vWF) is primarily synthesized by **endothelial cells** and **megakaryocytes** [1], not hepatocytes. - Hepatocytes are responsible for synthesizing other proteins like **clotting factors**, but not vWF. *Megakaryoctyes* - Megakaryocytes play a crucial role in the synthesis of **platelet-derived factors**, including von Willebrand factor (vWF) [1]. - They release vWF into the bloodstream, facilitating platelet adhesion, especially in vascular injury sites. *None* - The option implies all listed cell types synthesize vWF, which is incorrect, as **only endothelial cells and megakaryocytes** produce it [1]. - Suggests a misunderstanding of the synthesis of coagulation-related factors, as hepatocytes do not produce vWF. *Endothelial cells* - Endothelial cells are the primary source of **von Willebrand factor** [1], releasing it to assist in platelet aggregation and clotting. - They are essential for the body's response to vascular injury, facilitating hemostasis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 669-670.
Question 352: Type 3 respiratory failure occurs due to ?
- A. Post-operative atelectasis (Correct Answer)
- B. Kyphoscoliosis
- C. Flail chest
- D. Pulmonary fibrosis
Explanation: ***Post-operative atelectasis*** - **Type 3 respiratory failure**, also known as **perioperative respiratory failure**, is characterized by hypoxemia occurring typically after surgery. - **Atelectasis**, the collapse of lung tissue, is a common cause of hypoxemia in the post-operative period due to shallow breathing, pain, and anesthesia affecting lung volumes. *Kyphoscoliosis* - This condition leads to a **restrictive lung disease** due to chest wall deformity, causing chronic respiratory failure. [1] - It more typically results in **Type 2 respiratory failure** (hypercapnic) due to impaired ventilation over time. [1] *Flail chest* - Flail chest is a severe chest wall injury causing paradoxical movement, leading to **acute respiratory failure**. - It is often associated with **Type 1 (hypoxemic)** or **Type 2 (hypercapnic)** respiratory failure due to trauma-induced lung injury and impaired mechanics. *Pulmonary fibrosis* - This is a progressive interstitial lung disease causing **restrictive ventilatory defect** and impaired gas exchange. - It leads to chronic **Type 1 respiratory failure** (hypoxemic) as the lung tissue becomes stiff and scarred.
Pathology
1 questionsWhich of the following is a primary pleural tumor?
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 351: Which of the following is a primary pleural tumor?
- A. Mesothelioma (Correct Answer)
- B. Myxoma
- C. Lipoma
- D. None of the options
Explanation: ***Mesothelioma*** - Mesothelioma is a **primary malignant tumor** of the pleura [1], commonly associated with **asbestos exposure** [2]. - It typically presents with symptoms like **pleuritic chest pain**, dyspnea, and pleural effusion. *Myxoma* - Myxoma is a **benign tumor** primarily found in the **heart**, particularly in the left atrium, not in the pleura. - It does not arise from pleural tissue and lacks the **malignant characteristics** of mesothelioma. *All* - This option suggests that multiple tumors can be primary pleural tumors, which is incorrect as only mesothelioma is recognized as such. - Other tumors like myxoma and lipoma do not originate in the pleura and thus cannot be classified as primary pleural tumors. *Lipoma* - Lipoma is a **benign tumor** made up of adipose tissue [3] and is typically found in *subcutaneous tissue*, not the pleural cavity. - It does not have the malignant potential or association with pleural disease that characterizes mesothelioma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 728-729. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 339-340. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1222.
Physiology
4 questionsWhat does Boyle's Law state?
What is the primary function of the 'patch-clamp' technique in electrophysiology?
What is the role of gap junctions in cardiac muscle function?
When blood pressure falls below 40 mm Hg, which mechanism of regulation is working?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 351: What does Boyle's Law state?
- A. Pressure divided by temperature is constant.
- B. Volume divided by temperature is constant.
- C. PV = constant (Correct Answer)
- D. Pressure multiplied by volume equals the number of moles times the gas constant times temperature.
Explanation: ***PV = constant*** - **Boyle's Law** states that at constant temperature, the pressure and volume of a gas are inversely proportional. - Mathematically expressed as **PV = constant** or **P₁V₁ = P₂V₂** - This means that if the volume of a gas decreases, its pressure increases proportionally, and vice versa. - **Clinically relevant** in understanding lung mechanics during respiration - as thoracic volume increases during inspiration, intrapulmonary pressure decreases, allowing air to flow in. *Pressure divided by temperature is constant.* - This describes **Gay-Lussac's Law** (P/T = constant), which relates pressure and temperature at constant volume. - Shows the direct relationship between pressure and temperature. *Volume divided by temperature is constant.* - This statement describes **Charles's Law** (V/T = constant), which relates the volume and temperature of a gas at constant pressure. - Indicates a direct relationship between volume and temperature. *Pressure multiplied by volume equals the number of moles times the gas constant times temperature.* - This represents the **Ideal Gas Law**: PV = nRT - Combines Boyle's, Charles's, and Avogadro's laws to relate pressure, volume, temperature, and the number of moles of a gas.
Question 352: What is the primary function of the 'patch-clamp' technique in electrophysiology?
- A. To record facilitated diffusion
- B. To record osmotic pressure around semipermeable membrane
- C. To record RMP
- D. To record ionic currents through single or multiple ion channels (Correct Answer)
Explanation: ***To record ionic currents through single or multiple ion channels*** - The **patch-clamp technique** uses a microscopic glass pipette to form a tight seal with a cell membrane, allowing direct measurement of electrical currents flowing through individual or multiple **ion channels**. - This method is crucial for understanding the biophysical properties of **ion channels**, including their opening and closing kinetics, conductance, and sensitivity to various stimuli. *To record facilitated diffusion* - **Facilitated diffusion** is a passive transport process involving carrier proteins, which does not generate measurable electrical currents directly recorded by patch clamp. - While ion channels can facilitate diffusion, the patch-clamp technique specifically measures the **ionic current** generated by their activity, not the overall diffusive movement itself. *To record osmotic pressure around semipermeable membrane* - **Osmotic pressure** refers to the pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. - The patch-clamp technique is designed to measure electrical phenomena, not **osmotic pressure** or water movement across membranes. *To record RMP* - While the patch-clamp technique can be used in a **whole-cell configuration** to measure the **resting membrane potential (RMP)**, its primary and most distinctive function is to resolve **single ion channel activity**. - Other, simpler electrophysiological methods can also measure RMP, but patch-clamp excels at the high-resolution study of **ionic currents** through specific channels.
Question 353: What is the role of gap junctions in cardiac muscle function?
- A. Are not found in cardiac muscles
- B. Are not found in smooth muscles
- C. Have no significant role in cardiac muscle function
- D. Facilitate impulse transmission between cardiac myocytes (Correct Answer)
Explanation: ***Facilitate impulse transmission between cardiac myocytes*** - **Gap junctions** are specialized channels between adjacent cells that allow for direct communication and rapid movement of **ions** and small molecules. - In cardiac muscle, they form an essential part of **intercalated discs**, enabling the heart to function as a **syncytium** by allowing electrical impulses to spread quickly from one myocyte to another. *Are not found in cardiac muscles* - This statement is incorrect; **gap junctions** are a defining feature of **cardiac muscle** and are crucial for its coordinated contraction. - They are located within the **intercalated discs** that connect individual cardiac muscle cells. *Are not found in smooth muscles* - This statement is incorrect; **gap junctions** are indeed found in **smooth muscle**, particularly in single-unit smooth muscle, where they contribute to synchronized contractions, such as in the **gastrointestinal tract**. - They allow for the rapid propagation of electrical signals, leading to coordinated muscle activity. *Have no significant role in cardiac muscle function* - This statement is incorrect; **gap junctions** play a critically significant role in cardiac muscle function by ensuring the **rapid and synchronized spread of electrical impulses**. - Without functional gap junctions, the heart would not be able to contract efficiently or effectively as a pump.
Question 354: When blood pressure falls below 40 mm Hg, which mechanism of regulation is working?
- A. CNS ischemic reflex (Correct Answer)
- B. Chemoreceptor response
- C. Baroreceptor response
- D. None of the options
Explanation: ***CNS ischemic reflex*** - The **CNS ischemic reflex** is activated when blood pressure falls below 60 mmHg, with maximal activation below 40 mmHg, indicating severe ischemia in the brain's vasomotor center. - This reflex elicits an intense **sympathetic vasoconstriction** and cardiac stimulation to prioritize blood flow to the brain even at the expense of other organs. *Chemoreceptor response* - The chemoreceptor reflex is primarily activated by a decrease in **arterial pO2**, an increase in **pCO2**, or a decrease in **pH**. - While it can increase blood pressure, it is not the primary or most profound regulatory mechanism specifically triggered by extremely low blood pressure (below 40 mmHg) to prevent brain ischemia. *Baroreceptor response* - **Baroreceptors** are most sensitive to changes in blood pressure within the normal to moderately hypotensive range (e.g., 60-180 mmHg). - At very low pressures (below 40-50 mmHg), baroreceptors become **less sensitive** or "saturated," and their effectiveness in raising blood pressure significantly diminishes. *None of the options* - This option is incorrect because the **CNS ischemic reflex** specifically functions as a powerful, last-ditch mechanism to maintain cerebral blood flow during severe hypotension which is a life saving reflex during conditions like hemorrhage.