NEET-PG 2012 Practice Questions

Q: Which of the following statements about the Corpus Callosum is correct?

Connects the left and right hemispheres. ***Connects the left and right hemispheres*** - The **corpus callosum** is the largest **commissural white matter tract** in the brain, uniquely designed to facilitate communication between the **corresponding regions** of the left and right cerebral hemispheres [1]. - Its primary function is to integrate **sensory, motor, and cognitive information** processed in each hemisphere, ensuring coordinated brain activity [1]. *Connects distant areas of the two sides of the brain* - While it connects regions on the two sides of the brain, the statement is too broad and does not specify its role in connecting **corresponding** or **homologous** areas across the hemispheres. - Other fiber tracts (e.g., **anterior commissure**) also connect different areas between the two sides, but the corpus callosum is specific to the **cerebral hemispheres**. *Connects the two frontal lobes* - The corpus callosum connects all four lobes (frontal, parietal, temporal, occipital) between the two hemispheres, not exclusively the **frontal lobes**. - While it does contain fibers connecting the frontal lobes, this statement is **incomplete** and does not capture its overall function. *All of the options* - Since the other options are either **incorrect** or **incomplete**, this option cannot be correct. - The most accurate and encompassing description of the corpus callosum's function among the choices is connecting the left and right hemispheres.

Q: Which of the following is a tributary of the coronary sinus?

Great cardiac vein. ***Great cardiac vein*** - The **great cardiac vein** is a major tributary that drains into the **coronary sinus**, carrying deoxygenated blood from the anterior and left ventricular walls [1]. - It travels alongside the **anterior interventricular artery** (LAD) and then wraps around the left side of the heart to join the coronary sinus [1]. *Anterior cardiac vein* - The **anterior cardiac veins** typically collect blood directly into the **right atrium**, bypassing the coronary sinus [1]. - They primarily drain the anterior wall of the right ventricle. *Thebesian vein* - **Thebesian veins** (or venae cordis minimae) are small veins that drain blood from the **myocardium directly into the heart chambers**, predominantly the atria [1]. - They represent a direct communication between the myocardial capillaries and the heart chambers, not tributaries of the coronary sinus. *Smallest cardiac vein* - The term "smallest cardiac vein" is often used synonymously with **Thebesian veins** [1]. - These veins empty directly into the **heart chambers**, serving as an ancillary drainage system, rather than converging into the coronary sinus.

Q: What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?

Rhinion. ***Correct Answer: Rhinion*** - The **rhinion** is the **most prominent anterior point of the nasal bone**, often palpable as a slight bump or angulation on the dorsum of the nose. - It marks the anatomical location of the **osseocartilaginous junction** of the nasal dorsum, where the bony nasal framework transitions to the cartilaginous framework. - This is the key anatomical landmark that defines the transition from bone to cartilage in the external nose. *Incorrect: Nasion* - The **nasion** is located at the **root of the nose**, specifically at the most anterior and superior point of the nasofrontal suture. - It is a bony landmark and does not directly relate to the osseocartilaginous junction of the nasal dorsum. *Incorrect: Radix* - The **radix** (or nasal root) refers to the **uppermost part of the nose**, corresponding to the nasion. - It defines the point where the nose begins to project from the forehead and is a bony landmark, not directly related to the osseocartilaginous junction. *Incorrect: Columella* - The **columella** is the **fleshy, narrow strip of tissue that separates the nostrils**. - It forms the inferior segment of the nasal septum and is composed of skin, soft tissue, and the medial crura of the alar cartilages, thus having no direct relation to the osseocartilaginous junction of the nasal dorsum.

Q: Enzymes that move a molecular group from one molecule to another are known as -

Transferases. ***Transferases*** - **Transferases** are a class of enzymes that catalyze the transfer of a specific functional group (e.g., methyl, acetyl, phosphate) from one molecule (the donor) to another (the acceptor). - This broad category includes enzymes vital for many metabolic pathways, such as **kinases** (transferring phosphate groups) and **transaminases** (transferring amino groups). *Ligases* - **Ligases** are enzymes responsible for joining two large molecules together, typically by forming a new chemical bond. - This process usually involves the concomitant hydrolysis of a small, energy-rich molecule such as **ATP**, to provide the necessary energy for bond formation. *Dipeptidases* - **Dipeptidases** are a type of hydrolase enzyme that specifically cleaves the peptide bond within a **dipeptide**, releasing two free amino acids. - They are crucial for the final stages of protein digestion, breaking down small peptides into absorbable **amino acid units**. *Oxido-reductases* - **Oxido-reductases** are enzymes that catalyze **oxidation-reduction reactions** (redox reactions), where electrons are transferred from one molecule to another. - This class includes enzymes like **dehydrogenases** and **oxidases**, which play critical roles in cellular respiration and energy production.

Q: Chylomicron remnants are associated with ?

Apo-E. ***Apo-E*** - **Apolipoprotein E (Apo-E)** is a crucial apolipoprotein on the surface of chylomicron remnants, acting as a **ligand for the LDL receptor-related protein 1 (LRP1)** in the liver. - This binding facilitates the **hepatic uptake and clearance** of chylomicron remnants from circulation. *Apo-A* - **Apo-AI** is the primary apolipoprotein of **HDL** and plays a key role in reverse cholesterol transport by activating **lecithin-cholesterol acyltransferase (LCAT)**. - While chylomicrons *acquire* some Apo-AI from HDL, it is not the primary apolipoprotein defining their remnants' hepatic clearance. *Apo-C* - **Apo-CII** is a vital activator of **lipoprotein lipase (LPL)**, which metabolizes triglycerides in chylomicrons and VLDL. - **Apo-CIII** inhibits LPL and hinders receptor-mediated uptake, but **Apo-E** is the key for remnant recognition and uptake, not Apo-C in general. *Apo-B100* - **Apo-B100** is the main structural apolipoprotein of **LDL** and **VLDL**, serving as the ligand for the LDL receptor, mediating their hepatic uptake. - While chylomicrons have **Apo-B48**, which is a truncated form of Apo-B100, Apo-B100 itself is not found on chylomicron remnants.

Q: In the electron transport chain (ETC), which enzyme does cyanide inhibit?

Cytochrome c oxidase (Complex IV). ***Cytochrome c oxidase (Complex IV)*** - Cyanide binds to the **ferric iron (Fe3+)** in the heme a3 component of cytochrome c oxidase, blocking the final transfer of electrons to oxygen. - This inhibition effectively halts the entire **electron transport chain** and **oxidative phosphorylation**, leading to rapid cellular energy depletion. *Complex I (NADH dehydrogenase)* - While other toxins can inhibit Complex I (e.g., rotenone, amytal), **cyanide specifically targets Complex IV**. - Inhibition here prevents the entry of electrons from **NADH** into the ETC, but it's not cyanide's primary site of action. *Complex III (Cytochrome bc1 complex)* - Complex III is involved in transferring electrons from **ubiquinol** to cytochrome c, but it is not directly inhibited by cyanide. - Antimycin A is a well-known inhibitor of Complex III. *Complex II (Succinate dehydrogenase)* - Complex II directly receives electrons from **succinate** in the citric acid cycle and passes them to ubiquinone, bypassing Complex I. - Cyanide does not inhibit Complex II; inhibitors of this complex include malonate.

Q: What is the term for the collapse of a lung?

Atelectasis. ***Atelectasis*** - **Atelectasis** is the technical term for the **collapse of a lung** or a part of a lung, leading to reduced or absent gas exchange. - It can be caused by **obstruction of the airway** (e.g., mucus plug, foreign body) or external compression on the lung [1]. *Emphysema* - **Emphysema** is a chronic lung disease characterized by the **destruction of the alveoli**, leading to permanent enlargement of airspaces [2]. - It results in reduced elastic recoil of the lungs and is a type of **COPD (chronic obstructive pulmonary disease)** [2]. *Bronchiectasis* - **Bronchiectasis** is a chronic condition where the airways (bronchi) become **abnormally widened** and scarred. - This widening leads to a buildup of mucus, making the lungs vulnerable to **recurrent infections**. *Bronchitis* - **Bronchitis** is an inflammation of the lining of the bronchial tubes, which carry air to and from your lungs. - It typically causes a **cough** with mucus production and can be acute or chronic.

Q: Prostaglandins (PGs) in semen are secreted by?

Seminal vesicle. ***Seminal vesicle*** - The **seminal vesicles** are the primary source of **prostaglandins (PGs)** in semen, contributing significantly to the seminal fluid volume. - These PGs play a crucial role in promoting **sperm motility** and facilitating fertilization. *Prostate* - The **prostate gland** primarily secretes **citrate**, **acid phosphatase**, and **prostate-specific antigen (PSA)**, which contribute to sperm activation and semen liquefaction. - It does not significantly contribute to the prostaglandin content of semen. *Sperms* - **Spermatozoa** themselves primarily contribute genetic material and are not a significant source of prostaglandin synthesis in semen. - Their main function is fertilization, not the production of accessory gland secretions. *Testes* - The **testes** are responsible for **spermatogenesis** (sperm production) and the synthesis of **androgens** like testosterone. - They do not secrete prostaglandins into the seminal fluid.

Q: What is the primary mechanism of heat loss in a modern X-ray tube?

Radiation. ***Radiation*** - The **primary mechanism** of heat loss in a modern X-ray tube is **radiation** (infrared emission). - The anode surface reaches extremely high temperatures (>1000°C) during X-ray production, causing it to emit significant **infrared radiation**. - Modern X-ray tubes use **high-emissivity materials** (tungsten-rhenium alloys) on the anode to maximize radiative heat transfer. - Since the tube operates in a **vacuum**, radiation is the only effective mechanism for heat dissipation from the anode itself. *Evaporation* - **Evaporation** requires a liquid-to-gas phase change, which is not applicable in the solid-state environment of an X-ray tube anode. - The **vacuum environment** inside the tube prevents any evaporative cooling. - This mechanism is irrelevant for heat loss from the anode. *Conduction* - **Conduction** does transfer heat from the focal spot through the anode body to the rotor bearings. - However, this is heat transfer *within* the tube components, not the primary mechanism for heat loss *from the tube*. - Heat conducted through components must ultimately be dissipated by **radiation** (from anode) or **convection** (from housing via cooling oil). *Convection* - **Convection** requires fluid movement (liquid or gas), which cannot occur in the **vacuum** inside the X-ray tube envelope. - While cooling oil outside the tube uses convection to remove heat from the housing, this is secondary heat removal, not the primary mechanism of heat loss from the anode. - The anode loses heat primarily via **radiation** first, then that heat may be further managed by convection in the cooling system.

Question 1

Which of the following statements about the Corpus Callosum is correct?

Accepted Answer

Connects the left and right hemispheres

Answer

All of the options

Answer

Connects distant areas of the two sides of the brain

Answer

Connects the two frontal lobes

Question 2

Which of the following is a tributary of the coronary sinus?

Accepted Answer

Great cardiac vein

Answer

Anterior cardiac vein

Answer

Smallest cardiac vein

Answer

Thebesian vein

Question 3

What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?

Accepted Answer

Rhinion

Answer

Nasion

Answer

Radix

Answer

Columella

Question 4

Enzymes that move a molecular group from one molecule to another are known as -

Accepted Answer

Transferases

Answer

Ligases

Answer

Dipeptidases

Answer

Oxido-reductases

Question 5

What is the function of DNA ligase?

Accepted Answer

Joins the Okazaki fragments on the lagging strand by sealing the nicks between them.

Answer

Unwinding (denaturation) of dsDNA to provide an ssDNA template

Answer

Initiation of DNA synthesis and elongation

Answer

Initiates synthesis of RNA primers

Question 6

Chylomicron remnants are associated with ?

Accepted Answer

Apo-E

Answer

Apo-C

Answer

Apo-A

Answer

Apo-B100

Question 7

In the electron transport chain (ETC), which enzyme does cyanide inhibit?

Accepted Answer

Cytochrome c oxidase (Complex IV)

Answer

Complex II (Succinate dehydrogenase)

Answer

Complex I (NADH dehydrogenase)

Answer

Complex III (Cytochrome bc1 complex)

Question 8

What is the term for the collapse of a lung?

Accepted Answer

Atelectasis

Answer

Emphysema

Answer

Bronchitis

Answer

Bronchiectasis

Question 9

Prostaglandins (PGs) in semen are secreted by?

Accepted Answer

Seminal vesicle

Answer

Prostate

Answer

Sperms

Answer

Testes

Question 10

What is the primary mechanism of heat loss in a modern X-ray tube?

Accepted Answer

Radiation

Answer

Evaporation

Answer

Conduction

Answer

Convection

NEET-PG 2012

Anatomy

Biochemistry

Pathology

Physiology

Radiology