NEET-PG 2012 Practice Questions

Q: Which of the following is a traction epiphysis ?

Coracoid process of scapula. ***Coracoid process of scapula*** - A **traction epiphysis** (also called atavistic epiphysis) serves as an attachment site for muscles and tendons, transferring muscle force to the bone without bearing significant weight or forming articular surfaces. - The **coracoid process** is a classic example, anchoring the **pectoralis minor, coracobrachialis, and short head of biceps brachii**, as well as important ligaments (coracoclavicular and coracoacromial). - It develops from a separate ossification center purely for muscle and ligament attachment, not for articulation or weight-bearing. *Tibial condyles* - The **tibial condyles** are **pressure epiphyses** (articular epiphyses) that form the superior articular surface of the tibia. - They articulate with the femoral condyles to form the knee joint and bear significant weight during standing and movement. - Their primary function is joint formation and contribution to longitudinal bone growth. *Trochanter of femur* - The **greater and lesser trochanters** are large bony prominences that serve as muscle attachment sites, but they are better classified as **apophyses** rather than true traction epiphyses. - An **apophysis** is a secondary ossification center that does not contribute to longitudinal bone growth and serves primarily for muscle attachment. - While functionally similar to traction epiphyses, the term "traction epiphysis" is more specifically applied to structures like the coracoid process, tibial tuberosity, and calcaneal tuberosity. *Head of femur* - The **head of femur** is a classic **pressure epiphysis** that articulates with the acetabulum to form the hip joint. - It bears significant body weight and contributes to the longitudinal growth of the femur. - Its primary functions are joint formation and weight transmission, not muscle attachment.

Q: Which enzyme is required for cutting the DNA strand during synthesis?

Topoisomerase. ***Topoisomerase*** - **Topoisomerases** are enzymes essential for DNA replication; they induce temporary **single- or double-strand breaks** in DNA to relieve **supercoiling** ahead of the replication fork. - This cutting and rejoining activity prevents the DNA from becoming excessively tangled and facilitates the unwinding process required for synthesis. *DNA polymerase* - **DNA polymerase** is responsible for **synthesizing new DNA strands** by adding nucleotides, not for cutting the DNA backbone. - It works by moving along the template strand, reading the bases, and then adding complementary nucleotides to the growing DNA strand. *DNA ligase* - **DNA ligase** functions to **join DNA fragments** together by forming phosphodiester bonds, especially in sealing Okazaki fragments during lagging strand synthesis. - Its role is to ligate (join) cut strands, not to initiate cuts in the DNA. *Helicase* - **Helicase** unwinds the DNA double helix into single strands using ATP hydrolysis; it **separates the two strands** but does not cut the phosphodiester backbone. - This enzyme creates the replication fork by disrupting hydrogen bonds between base pairs, making the DNA accessible for replication machinery.

Q: Hydrolysis occurs at which step of urea cycle ?

Cleavage of arginine. ***Cleavage of arginine*** - The final step in the urea cycle, where **arginine** is hydrolyzed by the enzyme **arginase** to form **urea** and **ornithine**. - This reaction involves the addition of a **water molecule** across the guanidino group to release urea. *Formation of argininosuccinate* - This step involves the condensation of **citrulline** and **aspartate**, catalyzed by **argininosuccinate synthetase**. - It is an **ATP-dependent** reaction, not a hydrolysis. *Formation of citrulline* - Occurs when **carbamoyl phosphate** condenses with **ornithine**, catalyzed by **ornithine transcarbamylase**. - This reaction involves the removal of a phosphate group, not the addition of water. *Formation of ornithine* - **Ornithine** is a substrate for the formation of citrulline and is also regenerated at the end of the cycle from arginine. - Its formation from arginine is a **hydrolysis** reaction, but simply stating "formation of ornithine" is less specific than "cleavage of arginine," which directly describes the hydrolytic event.

Q: Which macronutrient has the highest thermogenic effect?

Proteins. ***Proteins*** - Proteins have the **highest thermogenic effect** (also known as the **thermic effect of food** or TEF) among macronutrients, typically ranging from **20-30%** of their caloric content. - This high TEF is due to the energy required for their **digestion**, **absorption**, and **metabolism** (e.g., deamination, protein synthesis), making them more metabolically "expensive" to process than fats or carbohydrates. *Fat* - Fat has the **lowest thermogenic effect**, accounting for approximately **0-3%** of its caloric content. - This low TEF is because fats are **easily absorbed** and stored, requiring minimal energy for their processing. *Carbohydrate* - Carbohydrates have an intermediate thermogenic effect, typically ranging from **5-10%** of their caloric content. - The energy expenditure for carbohydrate metabolism involves processes like **digestion**, **absorption**, and **glucose oxidation** or conversion to glycogen. *Alcohol* - While alcohol has a relatively high thermogenic effect (**20-25%**), it is **not classified as a macronutrient** in traditional nutritional science. - The three primary macronutrients are proteins, carbohydrates, and fats. Among these, **proteins** have the highest TEF.

Q: In which type of Hodgkin's Lymphoma are lacunar cells typically observed?

Nodular Sclerosis type. ***Nodular Sclerosis Type*** - **Lacunar cells** are characteristically seen in **Nodular Sclerosis Hodgkin lymphoma**, which is the most common subtype [1][3]. - These cells are large **Reed-Sternberg cells** with a distinctive morphology, typically found in **fibrous areas** of the lymph node [1]. *Mixed cellularity type* - This subtype is associated with a diverse cell population but does not primarily feature **lacunar cells** [2][4]. - It predominantly contains **Reed-Sternberg cells** without the specific morphology seen in nodular sclerosis [2]. *Lymphocyte predominant* - Lymphocyte predominant type mainly consists of **lymphocytes** with few Reed-Sternberg cells, and lacks **lacunar cells** [5]. - The histology is significantly different, exhibiting a more lymphocytic composition and not the classic lucent spaces [5]. *All of the above* - This option is incorrect as neither **Mixed cellularity** nor **Lymphocyte predominant** types contain **lacunar cells** [2][4][5]. - Lacunar cells are a distinctive feature solely of the **Nodular Sclerosis type** in Hodgkin lymphoma [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 616. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 616-618. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 558-559. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 559-560. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 618.

Q: All of the following provide protection against malaria except which of the following?

PNH. ***PNH*** - Paroxysmal Nocturnal Hemoglobinuria (PNH) does not provide any **protection against malaria**; it is an acquired bone marrow disorder. - While it leads to increased hemolysis and thrombosis, it does not affect **malaria susceptibility** directly. *Duffy blood group* - The Duffy blood group has specific antigens that are a **receptor for Plasmodium vivax**, making individuals with a Duffy-negative phenotype resistant to this type of malaria. - Therefore, Duffy blood group status can indeed serve as a protective factor against certain malaria strains. *Hereditary spherocytosis* - This condition results in **spherical red blood cells** [1], causing hemolytic anemia, but it does not confer protection against malaria. - People with hereditary spherocytosis do not have a lower prevalence of malaria and may still be susceptible to infection. *Sickle cell anemia* - Individuals with sickle cell anemia often exhibit **increased resistance to malaria**, especially against Plasmodium falciparum [2]. - The sickling of red blood cells under low oxygen conditions creates an unfavorable environment for the malarial parasites to thrive [2, 3].

Q: What is the venous hematocrit level at which you will diagnose polycythemia in a newborn?

65%. ***Correct: 65%*** - **Polycythemia** in a newborn is typically diagnosed when the **venous hematocrit** is **≥65%**. - This threshold indicates an abnormally high concentration of **red blood cells**, increasing blood viscosity. *Incorrect: 55%* - A venous hematocrit of 55% is generally considered within the **normal range** for a newborn, especially within the first few hours of life. - It does not meet the criteria for diagnosing **polycythemia**. *Incorrect: 60%* - While 60% is elevated compared to adult norms, it is still generally within the higher end of the **normal range** for an infant. - This level alone is usually **not sufficient** to diagnose **polycythemia** or warrant intervention without other clinical signs. *Incorrect: 70%* - A venous hematocrit of 70% definitely indicates **polycythemia** and significant **hyperviscosity**. - However, the diagnostic threshold for polycythemia is **65%**, meaning the condition is identified earlier.

Q: Gas exchange in tissues takes place at?

Capillary. ***Capillary*** - **Capillaries** are the smallest and most numerous blood vessels, with very thin walls (only one cell thick), which facilitates the efficient exchange of gases, nutrients, and waste products between blood and tissues. - Their extensive network ensures close proximity to nearly every cell in the body, maximizing the surface area and minimizing the diffusion distance for **gas exchange**. *Artery* - Arteries carry **oxygenated blood** away from the heart to the tissues but have thick, muscular walls designed for high pressure and transport, not for direct exchange with tissues. - They branch into smaller arterioles, which then lead to capillaries, making them a conduit rather than an exchange site. *Vein* - Veins carry **deoxygenated blood** back to the heart from the tissues and have relatively thin walls compared to arteries but are still too thick for efficient gas exchange. - They primarily serve as blood return vessels and reservoirs. *Venules* - Venules are small blood vessels that merge from capillaries and eventually combine to form veins; they primarily function in collecting blood from capillary beds. - While slightly more permeable than larger veins, their main role is still collection and transport, not the extensive gas exchange facilitated by capillaries.

Q: Which tract is responsible for the loss of proprioception and fine touch?

Dorsal column. ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.

Q: The primary site of vasopressin synthesis is

Supraoptic nucleus. ***Supraoptic nucleus*** - The **supraoptic nucleus** of the hypothalamus is the **primary site** for the synthesis of **vasopressin** (also known as antidiuretic hormone or ADH). - Approximately **80% of vasopressin** is produced by the neurosecretory cells in this nucleus. - The synthesized vasopressin is transported down axons to the posterior pituitary for storage and release. *Preoptic nucleus* - The **preoptic nucleus** is involved in various homeostatic functions, including **thermoregulation** and **sleep regulation**, but not the synthesis of vasopressin. - While it has neuronal connections to the hypothalamus, it does not produce ADH. *Paraventricular nucleus* - The **paraventricular nucleus** also synthesizes **both vasopressin and oxytocin**, accounting for approximately **20% of vasopressin production**. - While it does produce vasopressin, the **supraoptic nucleus remains the primary site**, making it the correct answer to this question. - The PVN also plays important roles in stress response and various autonomic functions. *Posterior pituitary* - The **posterior pituitary** (neurohypophysis) is responsible for the **storage and release** of vasopressin and oxytocin, not their synthesis. - These hormones are produced in the hypothalamic nuclei (supraoptic and paraventricular) and then transported down axonal tracts to the posterior pituitary.

Question 1

Which of the following is a traction epiphysis ?

Accepted Answer

Coracoid process of scapula

Answer

Tibial condyles

Answer

Head of femur

Answer

Trochanter of femur

Question 2

Which enzyme is required for cutting the DNA strand during synthesis?

Accepted Answer

Topoisomerase

Answer

DNA polymerase

Answer

DNA ligase

Answer

Helicase

Question 3

Hydrolysis occurs at which step of urea cycle ?

Accepted Answer

Cleavage of arginine

Answer

Formation of ornithine

Answer

Formation of argininosuccinate

Answer

Formation of citrulline

Question 4

Which macronutrient has the highest thermogenic effect?

Accepted Answer

Proteins

Answer

Fat

Answer

Carbohydrate

Answer

Alcohol

Question 5

In which type of Hodgkin's Lymphoma are lacunar cells typically observed?

Accepted Answer

Nodular Sclerosis type

Answer

Mixed cellularity type

Answer

Lymphocyte predominant type

Answer

All of the options

Question 6

All of the following provide protection against malaria except which of the following?

Accepted Answer

PNH

Answer

Sickle cell anemia

Answer

Hereditary spherocytosis

Answer

Duffy blood group

Question 7

What is the venous hematocrit level at which you will diagnose polycythemia in a newborn?

Accepted Answer

65%

Answer

55%

Answer

60%

Answer

70%

Question 8

Gas exchange in tissues takes place at?

Accepted Answer

Capillary

Answer

Artery

Answer

Vein

Answer

Venules

Question 9

Which tract is responsible for the loss of proprioception and fine touch?

Accepted Answer

Dorsal column

Answer

Anterior spinothalamic tract

Answer

Lateral spinothalamic tract

Answer

Corticospinal tract

Question 10

The primary site of vasopressin synthesis is

Accepted Answer

Supraoptic nucleus

Answer

Preoptic nucleus

Answer

Paraventricular nucleus

Answer

Posterior pituitary

NEET-PG 2012

Anatomy

Biochemistry

Pathology

Pediatrics

Physiology