Biochemistry
2 questionsWhat is the role of colipase in fat digestion?
Enzyme deficient in Hers disease -
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 241: What is the role of colipase in fat digestion?
- A. Encoded by the gene CLPS
- B. Assists pancreatic lipase in fat digestion (Correct Answer)
- C. Is secreted in an inactive form
- D. Is secreted by pancreatic cells
Explanation: ***Assists pancreatic lipase in fat digestion*** - Colipase **binds to pancreatic lipase** and the **lipid-water interface** of the fat droplet, providing a conformational change that enables lipase to access and hydrolyze triglycerides. - It also prevents bile salts from inactivating pancreatic lipase, ensuring efficient **fat emulsification and digestion**. *Is secreted in an inactive form* - Colipase is secreted as **procolipase** by the pancreas, which is then activated by **trypsin** in the duodenum. - While correct, this option describes its activation rather than its primary role in fat digestion. *Encoded by the gene CLPS* - The gene **CLPS** indeed encodes for colipase, but this is a genetic detail rather than its functional role in the digestive process. - Knowledge of the encoding gene is not directly relevant to understanding its biochemical function in fat digestion. *Is secreted by pancreatic cells* - Colipase is indeed synthesized and secreted by the **pancreas** into the small intestine. - This statement is true but describes the **origin** of colipase, not its specific functional role in fat digestion.
Question 242: Enzyme deficient in Hers disease -
- A. Muscle phosphorylase
- B. Liver phosphorylase (Correct Answer)
- C. Acid maltase
- D. Debranching enzyme
Explanation: ***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.
Pathology
2 questionsWhich type of necrosis is most commonly associated with the spread of infection?
Which substance plays a significant role in the tumor metastasis cascade?
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 241: Which type of necrosis is most commonly associated with the spread of infection?
- A. Fibrinoid necrosis
- B. Fat necrosis
- C. Liquefactive necrosis (Correct Answer)
- D. Coagulative necrosis
Explanation: ***Liquifactive necrosis*** - Caused by the enzymatic digestion of tissue, leading to the formation of liquid pus, typically associated with bacterial infections [1]. - Commonly occurs in the **brain** and in a tissue impacted by **pyogenic bacteria** [1], demonstrating how infection can lead to tissue damage. *Fat necrosis* - Primarily related to inflammation of fat tissue, often seen in pancreatitis or trauma to fat areas. - It is not directly caused by infections but rather by fat cell damage and necrosis, leading to **saponification**. *Fibrinoid necrosis* - Associated with **immune-mediated vascular injury**, seen in conditions like **vasculitis** or **malignant hypertension** [2]. - Characterized by the deposition of **fibrin-like protein** [2], not directly related to infectious processes. *Coagulative necrosis* - Typically occurs in ischemic conditions like myocardial infarction, where tissue architecture is preserved despite cell death. - It is not directly linked to infection spread, as it relates more to loss of blood supply rather than infectious agents. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 193-194. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 103-104.
Question 242: Which substance plays a significant role in the tumor metastasis cascade?
- A. TNF-alpha
- B. CD99
- C. NM23
- D. MMP-2 (Matrix Metalloproteinase-2) (Correct Answer)
Explanation: ***Collagenase IV*** - Collagenase IV is involved in the **degradation of extracellular matrix**, facilitating tumor invasion and metastasis [1,2]. - It plays a crucial role in breaking down **type IV collagen**, a major component of the **basement membrane**, allowing cancer cells to migrate [2]. *TNF-alpha* - While TNF-alpha is a cytokine that can promote **tumor growth**, it is not directly involved in the **metastatic cascade** like collagenase IV [3,4]. - It primarily functions in **inflammation** and immune response, affecting tumor microenvironment rather than directly facilitating invasion. *NM23* - NM23 is noted for its potential role as a **tumor suppressor**, and lower levels are associated with metastasis. - However, it does not play a direct role in the *metastatic cascade* itself [3,4], as it primarily influences **tumor progression** rather than matrix degradation. *CD99* - CD99 is a cell adhesion molecule implicated in **cell migration**, but it is not a significant factor in the **enzymatic breakdown** of tissue during metastasis [1,2]. - Its expression has more to do with **cell adhesion characteristics**, rather than directly promoting invasive capabilities. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 315-316. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 232-233. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 314-315. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 233-234.
Physiology
6 questionsSecretion of bile out of hepatocytes occurs via?
Intestinal absorption of calcium is mainly increased by?
Vitamin D absorption is decreased by ?
Chemotaxis is mediated by-
Cholecystokinin is produced from:
Which of the following statements about lung compliance is false?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 241: Secretion of bile out of hepatocytes occurs via?
- A. Passive diffusion
- B. Facilitated diffusion
- C. Osmosis
- D. Active transport (Correct Answer)
Explanation: ***Active transport*** - Bile secretion by hepatocytes is an **energy-dependent process** against concentration gradients, requiring specific transporter proteins. - This active mechanism ensures efficient bile flow and prevents reflux, crucial for processes like **fat digestion and absorption**. *Passive diffusion* - **Passive diffusion** involves substances moving down their concentration gradient without energy expenditure. - Bile components, like bile salts, are highly concentrated within hepatocytes and need to be moved against this gradient. *Facilitated diffusion* - This type of diffusion utilizes **transmembrane proteins** to move substances down their concentration gradient, but still does not directly consume ATP. - Bile components are often transported against their concentration gradient, which is not facilitated diffusion. *Osmosis* - **Osmosis** specifically refers to the movement of water across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration. - While water is a component of bile, the primary mechanism of moving bile solutes out of the hepatocyte is not osmosis.
Question 242: Intestinal absorption of calcium is mainly increased by?
- A. Calcitriol (Correct Answer)
- B. Parathormone
- C. Glucocorticoids
- D. ACTH
Explanation: ***Calcitriol*** - **Calcitriol** (1,25-dihydroxyvitamin D3) is the hormonally active form of vitamin D, which is essential for increasing **calcium absorption** from the intestines. - It stimulates the synthesis of **calcium-binding proteins** in intestinal epithelial cells, facilitating active transport of calcium. *Parathormone* - **Parathormone (PTH)** primarily regulates calcium by increasing its reabsorption in the **kidneys** and stimulating its release from **bones**. - While it indirectly promotes calcitriol synthesis, its *direct* effect on intestinal calcium absorption is minimal compared to calcitriol. *Glucocorticoids* - **Glucocorticoids** generally have an *inhibitory* effect on calcium absorption in the intestine and can also increase renal excretion of calcium. - Prolonged use can lead to **osteoporosis** due to their negative impact on bone formation and calcium balance. *ACTH* - **ACTH (adrenocorticotropic hormone)** primarily stimulates the adrenal cortex to produce **cortisol** and other glucocorticoids. - It has **no direct role** in regulating calcium absorption from the intestines.
Question 243: Vitamin D absorption is decreased by ?
- A. Proteins
- B. Acid
- C. Lactose
- D. Fat malabsorption (Correct Answer)
Explanation: ***Fat malabsorption*** - **Vitamin D** is a **fat-soluble vitamin**, meaning it requires dietary fat for proper absorption in the small intestine. - Conditions causing **fat malabsorption**, such as **cystic fibrosis**, **celiac disease**, or **pancreatic insufficiency**, significantly reduce the uptake of vitamin D. *Proteins* - **Proteins** do not directly decrease vitamin D absorption; in fact, some dietary proteins can enhance vitamin D binding and transport in the bloodstream. - Their primary role is in structural and enzymatic functions, not impeding fat-soluble vitamin uptake. *Acid* - **Gastric acid** is important for the absorption of some nutrients, but it generally does not directly hinder the absorption of **fat-soluble vitamins** like vitamin D. - Conditions like **achlorhydria** primarily affect the absorption of minerals and vitamin B12, rather than vitamin D. *Lactose* - **Lactose** is a sugar found in milk, and its malabsorption (lactose intolerance) primarily causes gastrointestinal symptoms like bloating and diarrhea. - It does not directly interfere with the absorption of **fat-soluble vitamins**; rather, it affects carbohydrate digestion.
Question 244: Chemotaxis is mediated by-
- A. Histamine
- B. Leukotriene C4 and C3a
- C. Bradykinin
- D. Leukotriene B4 and C5a (Correct Answer)
Explanation: ***Leukotriene B4 and C5a*** - Both **Leukotriene B4** [2] and **C5a** [1] are potent **chemoattractants** that guide the migration of neutrophils and other immune cells to sites of inflammation. - They are crucial in amplifying the **immune response**, particularly during acute inflammatory reactions. *Histamine* - Primarily involved in **vasodilation** and increased **vascular permeability**, rather than mediating chemotaxis. - Does not specifically attract immune cells to sites of injury or infection like leukotrienes do. *Bradykinin* - Mainly functions in **pain sensation** and promoting **vascular permeability**, not as a direct chemotactic agent. - It influences inflammation but does not effectively recruit immune cells to tissues. *Leukotriene C4 and C3a* - **Leukotriene C4** is involved in bronchoconstriction, while **C3a** [1] has roles in the complement system but is less potent than C5a in chemotaxis. - These mediators have different primary roles in inflammation, lacking the specificity of B4 and C5a for leukocyte attraction. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 99-100. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 95-96.
Question 245: Cholecystokinin is produced from:
- A. Hepatocyte
- B. Gastric mucosa
- C. Duodenal mucosa (Correct Answer)
- D. Epithelial cells of distal common bile duct
Explanation: ***Duodenal mucosa*** - **Cholecystokinin (CCK)** is primarily secreted by **I cells**, which are specialized enteroendocrine cells located in the **mucosa of the duodenum** and jejunum. - The release of CCK is stimulated by the presence of **fatty acids** and **amino acids** in the small intestine. *Hepatocyte* - **Hepatocytes** are the main functional cells of the liver, responsible for bile production, metabolism, and detoxification. - They **do not produce regulatory hormones** like cholecystokinin. *Gastric mucosa* - The **gastric mucosa** primarily produces **gastrin**, hydrochloric acid, and pepsinogen, which are involved in gastric digestion. - It does **not secrete cholecystokinin**, which is involved in stimulating gallbladder contraction and pancreatic enzyme release. *Epithelial cells of distal common bile duct* - The **epithelial cells of the common bile duct** are involved in bile transport and modification, but **not in hormone production**. - Their primary role is to line the duct and contribute to the composition of bile.
Question 246: Which of the following statements about lung compliance is false?
- A. Decreased in emphysema (Correct Answer)
- B. Total compliance is 0.2 L/cm H2O
- C. A measure of lung distensibility
- D. Change in volume per unit change in pressure
Explanation: ***Decreased in emphysema*** - This statement is **false** because **emphysema** is characterized by the destruction of elastic fibers in the lung parenchyma, which paradoxically leads to an **increase** in lung compliance. - The loss of elastic recoil makes the lungs more distensible and easier to inflate, but also impairs their ability to passively exhale. *Total compliance is 0.2 L/cm H2O* - This value represents the **normal total lung compliance** in a healthy adult (0.17 to 0.25 L/cm H2O), including both lung and chest wall compliance. - Lung compliance alone is typically around 0.2 L/cm H2O for healthy lungs. *A measure of lung distensibility* - **Compliance** is intrinsically defined as a measure of how easily the lungs or chest wall can be stretched or distended. - High compliance means the lungs are easy to inflate, while low compliance means they are stiff and difficult to inflate. *Change in volume per unit change in pressure* - This is the explicit **formula and definition of compliance** (C = ΔV/ΔP). - It quantifies the change in lung volume in response to a given change in transpulmonary pressure.