Anatomy
1 questionsWhat is the significance of the term 'Corona mortis' in human anatomy?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 571: What is the significance of the term 'Corona mortis' in human anatomy?
- A. Anastomosis between superior and inferior gluteal arteries
- B. A ligament connecting the pubic symphysis
- C. A nerve crossing the pelvic brim
- D. Anastomosis between obturator and inferior epigastric vessels (Correct Answer)
Explanation: ***Anastomosis between obturator and inferior epigastric vessels*** - **Corona mortis**, meaning "crown of death" in Latin, refers to a clinically significant vascular anastomosis that passes over the superior pubic ramus. - This anastomosis usually occurs between the **obturator artery** (a branch of the internal iliac artery) and the **inferior epigastric artery** (a branch of the external iliac artery), posing a risk of severe hemorrhage during surgical procedures in the retropubic space [1]. *Anastomosis between superior and inferior gluteal arteries* - While gluteal arteries do anastomose, they form a crucial part of the **cruciate anastomosis of the thigh**, not the corona mortis. - This anastomosis is important for blood supply to the hip joint and thigh musculature, far removed from the retropubic space. *A ligament connecting the pubic symphysis* - The pubic symphysis is connected by ligaments such as the **superior and arcuate pubic ligaments**, which provide stability to the joint. - These are fibrous structures and do not represent a vascular anastomosis. *A nerve crossing the pelvic brim* - Several nerves cross the pelvic brim, such as the **obturator nerve** or the **femoral nerve**, but these are neural structures. - The term corona mortis specifically refers to a **vascular connection**, not a nerve.
Biochemistry
3 questionsCitrate synthase is inhibited by -
Fumarate is formed from which amino acid?
Enzyme deficient in Hers disease -
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 571: Citrate synthase is inhibited by -
- A. Insulin
- B. Glucagon
- C. ADP
- D. ATP (Correct Answer)
Explanation: ***ATP*** - **Citrate synthase**, a key enzyme in the Krebs cycle, is inhibited by **high levels of ATP**, indicating a high energy state in the cell. - This allosteric inhibition helps regulate the metabolic flux through the cycle, slowing it down when energy is abundant. *ADP* - **ADP** typically signifies a low energy state and would generally act as an **activator** rather than an inhibitor for metabolic pathways that produce ATP. - In this context, ADP would promote the activity of enzymes involved in energy generation, including those in the Krebs cycle. *Insulin* - **Insulin** is a hormone that promotes fuel storage and utilization, generally **activating** metabolic pathways rather than directly inhibiting enzymes like citrate synthase. - Its primary role is to regulate blood glucose levels and promote glucose uptake and utilization. *Glucagon* - **Glucagon** is a hormone that mobilizes fuel from storage and is typically associated with **catabolic processes**, often increasing metabolic activity in response to low blood glucose. - It does not directly inhibit citrate synthase; its main actions are on glucoregulation.
Question 572: Fumarate is formed from which amino acid?
- A. Methionine
- B. Valine
- C. Histidine
- D. Tyrosine (Correct Answer)
Explanation: ***Tyrosine*** - **Tyrosine** is a **glucogenic and ketogenic amino acid** that is catabolized to acetoacetate and fumarate. - **Fumarate** then enters the **citric acid cycle (Krebs cycle)**, whereas acetoacetate is a ketone body. *Methionine* - **Methionine** is an **essential amino acid** and a precursor for **S-adenosylmethionine (SAM)**, a methyl donor in many reactions. - Its catabolism produces **succinyl CoA**, not fumarate, through a series of steps via propionyl CoA. *Valine* - **Valine** is a **branched-chain amino acid (BCAA)** that is exclusively **glucogenic**. - Its catabolism ultimately leads to the formation of **succinyl CoA**, which can enter the citric acid cycle. *Histidine* - **Histidine** is an **essential amino acid** that is catabolized to **formiminoglutamate (FIGLU)**. - FIGLU is then converted to **glutamate**, which can eventually be deaminated to α-ketoglutarate, a citric acid cycle intermediate, but not directly fumarate.
Question 573: 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.
Community Medicine
1 questionsWhat distance from a water source defines a problem village according to the Government of India?
NEET-PG 2015 - Community Medicine NEET-PG Practice Questions and MCQs
Question 571: What distance from a water source defines a problem village according to the Government of India?
- A. > 0.5 km
- B. > 1 km
- C. > 1.6 km (Correct Answer)
- D. None of the options
Explanation: ***> 1.6 km*** - According to the **Government of India's criteria**, a village is designated as a **problem village** if its residents have to travel more than **1.6 kilometers** to access a safe and assured source of drinking water. - This definition is crucial for identifying areas that require specific interventions and programs to improve water access. *> 0.5 km* - While a distance of 0.5 km might be considered inconvenient, it does not meet the **official threshold** set by the Government of India for categorizing a village as "problematic" regarding water access. - This distance is typically much shorter than the criteria used for policy and intervention planning. *> 1 km* - A distance of 1 km, like 0.5 km, falls short of the **established benchmark** of 1.6 km defined by the Government of India for identifying a problem village. - Although it represents a significant walk, it does not trigger the specific **policy responses** associated with problem village status. *None of the options* - This option is incorrect because **1.6 km** is indeed the specific distance recognized by the Government of India for defining a problem village in terms of water source accessibility. - The other options are incorrect as they do not match the official criteria.
Microbiology
4 questionsWhich bacteria can be isolated using crystal violet blood agar?
Which of the following is an example of the transfer of drug resistance by conjugation?
Multiple drug resistance is transferred through -
Which medium is most commonly used for antibiotic sensitivity testing?
NEET-PG 2015 - Microbiology NEET-PG Practice Questions and MCQs
Question 571: Which bacteria can be isolated using crystal violet blood agar?
- A. Corynebacterium diphtheriae
- B. Staph aureus
- C. Meningococcus
- D. β-hemolytic streptococci (Correct Answer)
Explanation: ***β-hemolytic streptococci*** - **Crystal violet blood agar** is a selective medium that inhibits the growth of most Gram-positive bacteria, except for **beta-hemolytic streptococci**. - The crystal violet dye suppresses the growth of competing flora, allowing for better isolation and identification of these bacteria, which exhibit **complete hemolysis (beta-hemolysis)** on blood agar. *Corynebacterium diphtheriae* - This bacterium requires more specialized media, such as **Tinsdale agar** or **Loeffler's serum agar**, for optimal growth and identification due to specific nutritional requirements and colony morphology. - Crystal violet blood agar is not the primary medium used for its isolation. *Staph aureus* - **Staphylococcus aureus** is a common contaminant that is typically inhibited by the crystal violet in the medium. - It grows well on routine blood agar but is not selectively grown or isolated using crystal violet blood agar. *Meningococcus* - **Neisseria meningitidis** (Meningococcus) requires enriched media like **chocolate agar** or **Thayer-Martin agar** for successful isolation, as it is a fastidious organism. - Crystal violet blood agar is not suitable for its growth due to its inhibitory properties and lack of necessary nutrients.
Question 572: Which of the following is an example of the transfer of drug resistance by conjugation?
- A. Staphylococci to rifampicin
- B. Pneumococcus to penicillin G
- C. M tuberculosis to antitubercular drugs
- D. E coli to streptomycin (Correct Answer)
Explanation: **E coli to streptomycin** - The transfer of **streptomycin resistance** in *E. coli* is a classic example of **conjugation**, mediated by **transferable R-plasmids**. - **Conjugation** involves direct cell-to-cell contact and the transfer of genetic material via a **pilus**, allowing for efficient spread of resistance genes. *Staphylococci to rifampicin* - **Rifampicin resistance** in *Staphylococci* (e.g., MRSA) primarily results from **chromosomal mutations** in the *rpoB* gene, which alters the drug's binding site. - This type of resistance usually arises through **spontaneous mutation and selection**, rather than active transfer via conjugation. *Pneumococcus to penicillin G* - **Penicillin resistance** in *Pneumococcus* (e.g., **PEN-R *S. pneumoniae***) is often due to alterations in **penicillin-binding proteins (PBPs)**, acquired through **transformation**. - Transformation involves the uptake of **naked DNA** from the environment, not direct cell-to-cell contact as in conjugation. *M tuberculosis to antitubercular drugs* - **Drug resistance** in *Mycobacterium tuberculosis* to antitubercular drugs (such as isoniazid and rifampicin) is predominantly mediated by **chromosomal mutations**. - These mutations occur within genes encoding drug targets or drug-activating enzymes, leading to altered drug sensitivity.
Question 573: Multiple drug resistance is transferred through -
- A. Transduction
- B. Transformation
- C. Conjugation (Correct Answer)
- D. Mutation
Explanation: ***Conjugation*** - Conjugation is a primary mechanism for the spread of **antibiotic resistance genes** among bacteria, including those responsible for multiple drug resistance. - It involves the direct transfer of **plasmids** (which often carry resistance genes) from one bacterial cell to another through a pilus. *Transduction* - Transduction is the process where bacteria acquire foreign DNA, including resistance genes, via a **bacteriophage (virus)**. - While it can transfer resistance, conjugation is a more common and clinically significant route for **multidrug resistance** spread. *Transformation* - Transformation involves the uptake of **naked DNA** from the environment by a bacterial cell. - While bacteria can acquire resistance genes this way, it is less efficient for widespread, rapid transfer of **multiple resistance traits** compared to conjugation. *Mutation* - Mutation refers to a change in the bacterial organism's own DNA, which can lead to the development of **drug resistance**. - However, mutation explains the *origin* of resistance in a single bacterium, not the *transfer* of resistance genes (especially multiple resistance) between different bacteria.
Question 574: Which medium is most commonly used for antibiotic sensitivity testing?
- A. CLED agar
- B. Mueller-Hinton agar (Correct Answer)
- C. Blood agar
- D. MacConkey agar
Explanation: ***Mueller-Hinton agar*** - It is specifically formulated to provide optimal conditions for bacterial growth and **diffusion of antibiotics**, ensuring accurate and reproducible results for sensitivity testing. - Its **low concentration of sulfonamide inhibitors (thymidine and thymine)** and proper calcium and magnesium levels are crucial for accurate results for particular antibiotics. - It is the **gold standard medium** recommended by CLSI (Clinical and Laboratory Standards Institute) for the Kirby-Bauer disk diffusion method. *Blood agar* - Blood agar is a **general-purpose enrichment medium** that supports the growth of a wide range of fastidious microorganisms and is used to detect hemolytic reactions. - While many bacteria grow on blood agar, its composition and opacity can **interfere with precise zone of inhibition measurements** in antibiotic susceptibility testing. *MacConkey agar* - MacConkey agar is a **selective and differential medium** used for the isolation of Gram-negative enteric bacteria and differentiation based on lactose fermentation. - Its selective agents (bile salts and crystal violet) and pH indicators would **interfere with the standardized conditions** required for accurate antibiotic sensitivity testing. *CLED agar* - **Cystine-Lactose-Electrolyte-Deficient (CLED) agar** is primarily used for the isolation and enumeration of urinary tract pathogens, as it prevents the swarming of *Proteus* species and differentiates lactose fermenters from non-fermenters. - It is **not optimized** for antibiotic diffusion or inhibition of bacterial growth in the same way Mueller-Hinton is.
Physiology
1 questionsThe major role of 2,3-bisphosphoglycerate in RBCs is -
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 571: The major role of 2,3-bisphosphoglycerate in RBCs is -
- A. Acid-base balance
- B. Reversal of glycolysis
- C. Release of oxygen (Correct Answer)
- D. Binding of oxygen
Explanation: ***Release of oxygen*** - **2,3-bisphosphoglycerate (2,3-BPG)** binds allosterically to **deoxyhemoglobin**, stabilizing its T (tense) state. - This binding reduces hemoglobin's affinity for oxygen, promoting the **release of oxygen** to tissues. *Acid-base balance* - While red blood cells play a role in **acid-base balance** through the bicarbonate buffer system, 2,3-BPG's primary role is not buffering. - The **chloride shift** and **carbonic anhydrase** are more directly involved in RBC acid-base regulation. *Reversal of glycolysis* - 2,3-BPG is an intermediate of the **Rapoport-Luebering shunt**, a side pathway of glycolysis. - It does not reverse glycolysis but rather is produced during glycolysis to serve a specific function in oxygen transport. *Binding of oxygen* - 2,3-BPG **decreases** hemoglobin's affinity for oxygen, thus promoting its *release* from hemoglobin, not its binding. - Oxygen binding to hemoglobin occurs primarily at the **heme iron** without 2,3-BPG.