FMGE 2010 — Biochemistry

Q: Wernicke-Korsakoff's syndrome is due to the deficiency of:

Thiamine. ***Correct: Thiamine*** - **Wernicke-Korsakoff syndrome** is a severe neurological disorder caused by a profound deficiency of **thiamine (vitamin B1)**, most commonly seen in chronic alcoholics - **Thiamine** is crucial for **glucose metabolism** in the brain, and its deficiency leads to impaired neuronal function and brain damage - **Wernicke encephalopathy** presents acutely with confusion, ataxia, and ophthalmoplegia - **Korsakoff psychosis** represents the chronic phase with profound memory impairment and confabulation *Incorrect: Pyridoxine* - Deficiency of **pyridoxine (vitamin B6)** can cause peripheral neuropathy, seizures, and sideroblastic anemia, but is not the cause of Wernicke-Korsakoff syndrome - **Isoniazid** treatment is a common cause of pyridoxine deficiency *Incorrect: Riboflavin* - **Riboflavin (vitamin B2)** deficiency leads to cheilosis, angular stomatitis, glossitis, and seborrheic dermatitis, but is not associated with Wernicke-Korsakoff syndrome - It plays a vital role as a coenzyme (FAD, FMN) in various **redox reactions** *Incorrect: Vitamin B12* - Deficiency of **vitamin B12 (cobalamin)** causes megaloblastic anemia and subacute combined degeneration of the spinal cord, with distinct neurological symptoms different from Wernicke-Korsakoff syndrome - **Intrinsic factor** is necessary for its absorption in the terminal ileum [Practice more Biochemistry PYQs on OnCourse]

Q: Fluoride, used in the collection of blood samples, inhibits which enzyme?

Enolase. ***Enolase*** - Fluoride is a potent inhibitor of **enolase**, an enzyme in the **glycolytic pathway**. - Inhibition of enolase prevents the conversion of **2-phosphoglycerate** to **phosphoenolpyruvate**, thereby halting glycolysis in collected blood samples. *Glucokinase* - Glucokinase is an enzyme primarily found in the **liver** and **pancreatic beta cells** that phosphorylates glucose. - Fluoride does not directly inhibit glucokinase; its primary site of action for preventing glycolysis in blood samples is enolase. *Glucose-6-phosphatase* - This enzyme is crucial for **glucose production** in the liver and kidneys, facilitating the dephosphorylation of **glucose-6-phosphate** to glucose. - Fluoride does not specifically target glucose-6-phosphatase as its mechanism for preventing glycolysis. *Hexokinase* - Hexokinase catalyzes the first step of glycolysis, phosphorylating **glucose to glucose-6-phosphate**. - While essential for glycolysis, hexokinase is not the primary target of fluoride's inhibitory action in blood collection, which specifically aims to stop the entire pathway further downstream at enolase. [Practice more Biochemistry PYQs on OnCourse]

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Wernicke-Korsakoff's syndrome is due to the deficiency of:

Fluoride, used in the collection of blood samples, inhibits which enzyme?

FMGE 2010 - Biochemistry FMGE Practice Questions and MCQs

Question 1: Wernicke-Korsakoff's syndrome is due to the deficiency of:

A. Pyridoxine
B. Riboflavin
C. Thiamine (Correct Answer)
D. Vitamin B12

Explanation: ***Correct: Thiamine*** - **Wernicke-Korsakoff syndrome** is a severe neurological disorder caused by a profound deficiency of **thiamine (vitamin B1)**, most commonly seen in chronic alcoholics - **Thiamine** is crucial for **glucose metabolism** in the brain, and its deficiency leads to impaired neuronal function and brain damage - **Wernicke encephalopathy** presents acutely with confusion, ataxia, and ophthalmoplegia - **Korsakoff psychosis** represents the chronic phase with profound memory impairment and confabulation *Incorrect: Pyridoxine* - Deficiency of **pyridoxine (vitamin B6)** can cause peripheral neuropathy, seizures, and sideroblastic anemia, but is not the cause of Wernicke-Korsakoff syndrome - **Isoniazid** treatment is a common cause of pyridoxine deficiency *Incorrect: Riboflavin* - **Riboflavin (vitamin B2)** deficiency leads to cheilosis, angular stomatitis, glossitis, and seborrheic dermatitis, but is not associated with Wernicke-Korsakoff syndrome - It plays a vital role as a coenzyme (FAD, FMN) in various **redox reactions** *Incorrect: Vitamin B12* - Deficiency of **vitamin B12 (cobalamin)** causes megaloblastic anemia and subacute combined degeneration of the spinal cord, with distinct neurological symptoms different from Wernicke-Korsakoff syndrome - **Intrinsic factor** is necessary for its absorption in the terminal ileum

Question 2: Fluoride, used in the collection of blood samples, inhibits which enzyme?

A. Enolase (Correct Answer)
B. Glucokinase
C. Glucose-6-phosphatase
D. Hexokinase

Explanation: ***Enolase*** - Fluoride is a potent inhibitor of **enolase**, an enzyme in the **glycolytic pathway**. - Inhibition of enolase prevents the conversion of **2-phosphoglycerate** to **phosphoenolpyruvate**, thereby halting glycolysis in collected blood samples. *Glucokinase* - Glucokinase is an enzyme primarily found in the **liver** and **pancreatic beta cells** that phosphorylates glucose. - Fluoride does not directly inhibit glucokinase; its primary site of action for preventing glycolysis in blood samples is enolase. *Glucose-6-phosphatase* - This enzyme is crucial for **glucose production** in the liver and kidneys, facilitating the dephosphorylation of **glucose-6-phosphate** to glucose. - Fluoride does not specifically target glucose-6-phosphatase as its mechanism for preventing glycolysis. *Hexokinase* - Hexokinase catalyzes the first step of glycolysis, phosphorylating **glucose to glucose-6-phosphate**. - While essential for glycolysis, hexokinase is not the primary target of fluoride's inhibitory action in blood collection, which specifically aims to stop the entire pathway further downstream at enolase.