NEET-PG 2013 Practice Questions

Q: Which of the following is not a tributary of the cavernous sinus?

Inferior cerebral vein. Detailed anatomical knowledge of the dural venous sinuses is required to answer this question. Venous drainage from the brain by way of the deep veins and dural sinuses typically empties principally into the internal jugular veins, though blood also drains via the ophthalmic and pterygoid venous plexuses [1]. ***Inferior cerebral vein*** - The **inferior cerebral veins** drain the inferior surface of the cerebral hemispheres and typically empty into the **basal vein of Rosenthal**, **transverse sinus**, or other dural sinuses. - They do **not directly drain** into the cavernous sinus, making this the correct answer. - While some small inferior cerebral veins may occasionally communicate with the cavernous sinus, they are not considered standard tributaries. *Central vein of retina* - The **central vein of retina** drains the retina and exits the eye through the optic nerve. - It drains into the **superior ophthalmic vein**, which then empties into the cavernous sinus. - It is an **indirect tributary** via the superior ophthalmic vein, not a direct tributary itself. *Sphenoparietal sinus* - The **sphenoparietal sinus** is a dural venous sinus that runs along the posterior edge of the lesser wing of the sphenoid bone. - It is a **direct tributary** that drains anteriorly into the cavernous sinus. - This is one of the standard tributaries listed in anatomical texts. *Superior ophthalmic vein* - The **superior ophthalmic vein** is the **major tributary** draining orbital structures including the eyeball, extraocular muscles, and eyelids. - It passes posteriorly through the **superior orbital fissure** to drain directly into the cavernous sinus. - This is the most clinically significant tributary, as infections can spread from the face to the cavernous sinus via this route.

Q: What is Galen's anastomosis?

Internal laryngeal nerve and recurrent laryngeal nerve. ***Internal laryngeal nerve and recurrent laryngeal nerve*** - **Galen's anastomosis** (also known as **ansa Galeni**) is the connection between the **internal laryngeal nerve** (a sensory branch of the superior laryngeal nerve) and the **recurrent laryngeal nerve** (motor branch of the vagus nerve). - This anastomosis occurs in the **laryngeal mucosa** and allows for communication between these two important nerves. - The **internal laryngeal nerve** provides **sensory innervation** to the larynx above the vocal cords, while the **recurrent laryngeal nerve** provides **motor innervation** to most intrinsic laryngeal muscles (except cricothyroid). - This anastomosis is clinically significant in understanding the complex innervation patterns of the larynx. *Recurrent laryngeal nerve and external laryngeal nerve* - While both nerves are branches of the vagus nerve and innervate laryngeal structures, this connection does not constitute **Galen's anastomosis**. - The recurrent laryngeal nerve innervates intrinsic laryngeal muscles (except cricothyroid), while the external laryngeal nerve innervates the **cricothyroid muscle** and is motor in nature. *None of the options* - This option is incorrect because the correct definition of **Galen's anastomosis** is provided in the first option. *Recurrent laryngeal nerve and sympathetic trunk* - While there may be sympathetic contributions to laryngeal innervation, this does not represent **Galen's anastomosis**. - The sympathetic trunk provides autonomic innervation but the specific named anastomosis refers to the connection between the internal laryngeal and recurrent laryngeal nerves.

Q: Kcat/Km is a measure of which of the following?

Enzyme efficiency. **Correct: Enzyme efficiency** - The ratio **kcat/Km** is the definitive measure of an enzyme's **catalytic efficiency** or **specificity constant** - It reflects how effectively an enzyme converts substrate to product at low substrate concentrations - A higher **kcat/Km** value indicates greater efficiency, combining high catalytic rate (kcat) with strong substrate affinity (low Km) - This is the most important parameter for comparing different enzymes or different substrates for the same enzyme *Incorrect: Speed of enzymatic reaction* - **kcat** (turnover number) alone measures the maximum speed when enzyme is saturated with substrate - **kcat/Km** is a more comprehensive measure that includes substrate binding affinity, not just reaction speed - Speed also depends on enzyme and substrate concentrations, which kcat/Km doesn't directly represent *Incorrect: Concentration of substrate* - **Km** (Michaelis constant) represents the substrate concentration at which reaction velocity is half of Vmax - **kcat/Km** is a ratio that describes enzyme performance across substrate concentrations, not the concentration itself - It's particularly useful for predicting enzyme behavior at physiological (low) substrate concentrations *Incorrect: Enzyme turnover* - **kcat** specifically measures enzyme turnover: the number of substrate molecules converted per enzyme molecule per unit time at saturation - **kcat/Km** incorporates both kcat and Km, providing overall efficiency rather than just turnover rate - Turnover is only one component of the efficiency measure

Q: Carboxypeptidase contains which mineral?

Zinc. ***Zinc*** - **Carboxypeptidase** is a **metalloenzyme**, meaning it requires a metal ion for its catalytic activity. - **Zinc** acts as a crucial cofactor in the active site of carboxypeptidase, enabling its proteolytic function. *Copper* - **Copper** is a component of enzymes like **cytochrome c oxidase** and **superoxide dismutase**, but not carboxypeptidase. - Its presence is essential for processes like **electron transport** and **antioxidant defense**. *Iron* - **Iron** is a central component of **hemoglobin** and **myoglobin** for oxygen transport, and in enzymes like **catalase** and **peroxidase**. - It is not involved in the catalytic mechanism of carboxypeptidase. *None of the options* - This option is incorrect because **Zinc** is a known and essential mineral for the function of carboxypeptidase. - Carboxypeptidase is a metalloenzyme, and a metal cofactor is required for its activity.

Q: Concentration of which is inversely related to the risk of coronary heart disease?

HDL. ***HDL*** - **High-density lipoprotein (HDL)** is known as "good cholesterol" because it helps remove excess cholesterol from the arteries and transport it back to the liver for excretion. - Higher levels of HDL are generally associated with a **lower risk of coronary heart disease (CHD)**, hence the inverse relationship. *VLDL* - **Very low-density lipoprotein (VLDL)** carries triglycerides and cholesterol and is considered an independent risk factor for CHD when present in high concentrations. - High VLDL levels are associated with an **increased risk of CHD**, not an inverse relationship. *LDL* - **Low-density lipoprotein (LDL)** is often referred to as "bad cholesterol" because it contributes to plaque buildup in arteries (**atherosclerosis**). - High levels of LDL are strongly associated with an **increased risk of CHD**, indicating a direct, not inverse, relationship. *None of the options* - This option is incorrect because HDL clearly demonstrates an **inverse relationship** with the risk of coronary heart disease.

Q: Reducing equivalents produced in glycolysis are transported from cytosol to mitochondria by ?

Malate-aspartate shuttle. ***Malate shuttle*** - The **malate-aspartate shuttle** is a primary mechanism for transporting **NADH reducing equivalents** from the cytosol to the mitochondrial matrix for **oxidative phosphorylation**. - It involves a series of **enzymes and transporters** that indirectly move electrons from NADH by converting **oxaloacetate to malate** in the cytosol, which then enters the mitochondria. *Carnitine* - **Carnitine** is primarily involved in the transport of **long-chain fatty acids** into the mitochondrial matrix for **beta-oxidation**. - It is not directly involved in the shuttle of NADH reducing equivalents generated during glycolysis. *Creatine* - **Creatine** and its phosphorylated form, **phosphocreatine**, are crucial for **energy buffering and transport** in tissues with high and fluctuating energy demands, like muscle and brain. - The creatine-phosphocreatine shuttle facilitates the rapid regeneration of ATP, but it is not involved in transporting glycolytic reducing equivalents. *Glutamate shuttle* - While glutamate and aspartate are components of the **malate-aspartate shuttle**, there isn't a standalone "glutamate shuttle" for transporting glycolytic reducing equivalents. - The **glutamate-aspartate transaminase** is an enzyme within the malate-aspartate shuttle, converting oxaloacetate to aspartate and alpha-ketoglutarate to glutamate from the matrix to the cytosol.

Q: Which of the following is NOT a feature of Peutz-Jeghers syndrome?

Autosomal recessive inheritance. ***High risk of malignancy*** - Peutz-Jeghers syndrome is primarily associated with **benign hamartomatous polyps**, not a **high risk of malignancy**, which distinguishes it from other syndromes. - Although patients may develop cancers [1], the syndrome itself does not inherently denote a high malignancy risk like other syndromes such as familial adenomatous polyposis. *Autosomal dominant* - This syndrome is indeed **autosomal dominant**, caused by mutations in the STK11 gene. - Families with this condition typically show **vertical transmission**, characteristic of autosomal dominant inheritance. *Hamartomatous polyp* - Individuals with Peutz-Jeghers syndrome develop **hamartomatous polyps**, which are a hallmark feature of the condition [1]. - These polyps can occur in the gastrointestinal tract and are benign lesions rather than adenomatous type seen in other syndromes [1]. *Mucocutaneous pigmentation* - Mucocutaneous pigmentation, such as **freckling around the lips and buccal mucosa**, is a key clinical feature of Peutz-Jeghers syndrome. - This pigmentation usually appears in childhood and is often a distinguishing sign of the syndrome.

Q: Response to iron therapy in iron deficiency anemia is denoted by?

Reticulocytosis. Reticulocytosis - Reticulocytosis is one of the earliest signs of a positive response to iron therapy in iron deficiency anemia, occurring within 5-10 days. - It signifies that the bone marrow is effectively producing new red blood cells after iron supplementation. Restoration of enzymes - While iron is a crucial component of many enzymes (e.g., catalase, cytochrome oxidase), its restoration takes time and is not the primary immediate indicator of therapeutic response. - Clinical improvement and other hematological parameters precede the full restoration of enzyme function. Increase in hemoglobin - An increase in hemoglobin is a definitive sign of successful treatment, but it occurs later than reticulocytosis, typically visible after several weeks to months of therapy. - Hemoglobin levels rise as the new, iron-sufficient red blood cells fully mature and replace the older, iron-deficient ones. Increase in iron binding capacity - In iron deficiency anemia, total iron-binding capacity (TIBC) is typically increased due to more transferrin being available to bind iron [1]. - Successful iron therapy would lead to a decrease in TIBC as transferrin sites become saturated with iron, not an increase.

Q: Which of the following is the primary site of gastrin production?

Gastric G cells. ***Gastric G cells*** - **G cells**, primarily located in the **antrum of the stomach**, are the main site for **gastrin production** - Gastrin is a hormone that stimulates the secretion of **gastric acid** by the parietal cells in the oxyntic glands of the stomach - G cells are specialized endocrine cells that release gastrin in response to gastric distension, amino acids, and vagal stimulation *Pancreas* - The pancreas produces hormones such as **insulin** and **glucagon**, and digestive enzymes like **amylase** and **lipase** - While the pancreas does contain some hormone-producing cells, it is not the primary site for gastrin synthesis *Pituitary gland* - The **pituitary gland** is the master endocrine gland, regulating various **hormonal axes** like thyroid, adrenal, and reproductive functions - It does not produce gastrin; its hormones include **growth hormone**, **prolactin**, **TSH**, **ACTH**, **FSH**, and **LH** *Gastric chief cells* - Chief cells (also called zymogenic cells) are located in the **gastric glands of the fundus and body** of the stomach - They produce **pepsinogen**, the inactive precursor of the proteolytic enzyme pepsin, not gastrin

Q: What is the blood supply of the liver in ml/min/100g?

50-60 ml/min/100g. ***50-60 ml/min/100g*** - The liver receives a substantial blood supply, but when expressed per 100 grams of tissue, the value is around **50-60 mL/min/100g**. This demonstrates the organ's high metabolic demand. - This value represents the total blood flow from both the **hepatic artery** and the **portal vein** per unit weight of liver tissue. *1500-2000 ml/min/100g* - This value is extremely high and does not accurately represent the **blood flow per 100g of liver tissue**. Such a high flow rate would imply an unrealistic perfusion. - While the total blood flow to the liver is large, it's not at this magnitude when normalized to tissue weight. *1000-1500 ml/min/100g* - This range is closer to the **total blood flow to the entire liver** (1000-1800 ml/min), not the blood flow per 100 grams of tissue. - It's crucial to differentiate between total organ flow and flow density (per 100g). *250-300 ml/min/100g* - This value is significantly higher than the actual blood supply per 100g of liver tissue, suggesting an overestimation of the **perfusion density**. - While the liver is highly perfused, this rate is not physiologically accurate when normalized to the tissue weight.

Question 1

Which of the following is not a tributary of the cavernous sinus?

Accepted Answer

Inferior cerebral vein

Answer

Central vein of retina

Answer

Sphenoparietal sinus

Answer

Superior ophthalmic vein

Question 2

What is Galen's anastomosis?

Accepted Answer

Internal laryngeal nerve and recurrent laryngeal nerve

Answer

Recurrent laryngeal nerve and external laryngeal nerve

Answer

None of the options

Answer

Recurrent laryngeal nerve and sympathetic trunk

Question 3

Kcat/Km is a measure of which of the following?

Accepted Answer

Enzyme efficiency

Answer

Speed of enzymatic reaction

Answer

Concentration of substrate

Answer

Enzyme turnover

Question 4

Carboxypeptidase contains which mineral?

Accepted Answer

Zinc

Answer

Copper

Answer

Iron

Answer

None of the options

Question 5

Concentration of which is inversely related to the risk of coronary heart disease?

Accepted Answer

HDL

Answer

VLDL

Answer

LDL

Answer

None of the options

Question 6

Reducing equivalents produced in glycolysis are transported from cytosol to mitochondria by ?

Accepted Answer

Malate-aspartate shuttle

Answer

Carnitine

Answer

Creatine

Answer

Glutamate shuttle

Question 7

Which of the following is NOT a feature of Peutz-Jeghers syndrome?

Accepted Answer

Autosomal recessive inheritance

Answer

Mucocutaneous pigmentation

Answer

Autosomal dominant

Answer

Hamartomatous polyp

Question 8

Response to iron therapy in iron deficiency anemia is denoted by?

Accepted Answer

Reticulocytosis

Answer

Increase in hemoglobin

Answer

Restoration of enzymes

Answer

Increase in iron binding capacity

Question 9

Which of the following is the primary site of gastrin production?

Accepted Answer

Gastric G cells

Answer

Gastric chief cells

Answer

Pancreas

Answer

Pituitary gland

Question 10

What is the blood supply of the liver in ml/min/100g?

Accepted Answer

50-60 ml/min/100g

Answer

1500-2000 ml/min/100g

Answer

1000-1500 ml/min/100g

Answer

250-300 ml/min/100g

NEET-PG 2013

Anatomy

Biochemistry

Internal Medicine

Physiology