NEET-PG 2023 - Biochemistry PYQs Practice Questions

Q: A 45-year-old male patient presents to the emergency department with severe pain and swelling in the big toe joint. He has a history of recurrent joint pain and dietary indiscretion. A specimen from the affected joint is subjected to a test that produces a purple color reaction. What is the test being performed?

Murexide test for uric acid detection. ***Murexide test for uric acid detection*** - The patient's presentation with **severe pain and swelling in the big toe**, recurrent joint pain, and dietary indiscretion is highly suggestive of **gout**, which is caused by the accumulation of **uric acid crystals**. - The **Murexide test** is a specific qualitative chemical test used to detect the presence of **uric acid** and its derivatives, yielding a characteristic **purple** color in the presence of uric acid. *Florence test for choline compounds* - The **Florence test** is used to identify **choline compounds**, primarily in forensic science for detecting **spermatozoa** by reacting with choline to form dark brown or black crystals. - While it involves a chemical reaction, its application and the compounds it detects are unrelated to the diagnosis of **gout** or uric acid. *Teichmann test for blood* - The **Teichmann test** (hemin test) is a microscopic chemical test used to confirm the presence of **blood** by detecting **hemin crystals**. - This test is not used for diagnosing joint conditions like gout or identifying **uric acid**. *Acid phosphatase test for prostate* - The **acid phosphatase test** measures the level of **acid phosphatase**, an enzyme mainly found in the **prostate gland**, and is used as a marker for **prostate cancer** or other prostatic conditions. - This test is entirely unrelated to the diagnosis of **gout** or the detection of **uric acid** in synovial fluid. [Practice more Biochemistry PYQs on OnCourse]

Q: A child presents with bone pain and hepatosplenomegaly, indicative of Gaucher's disease. A trephine biopsy and aspirate show the following finding. Which of the following is the most likely enzyme deficient in this condition?

Glucocerebrosidase. ***Correct: Glucocerebrosidase*** - The clinical presentation of **bone pain**, **hepatosplenomegaly**, and the characteristic histological finding of **lipid-laden macrophages** (Gaucher cells) with a **crinkled paper** appearance in the bone marrow aspirate are highly suggestive of **Gaucher's disease**. - **Gaucher's disease** is caused by a deficiency of the lysosomal enzyme **glucocerebrosidase**, leading to the accumulation of **glucocerebroside**. *Incorrect: Hexosaminidase* - Deficiency of **hexosaminidase A** is associated with **Tay-Sachs disease**, which presents with neurological degeneration but typically **lacks hepatosplenomegaly** and bone pain. - The histological findings in Tay-Sachs disease would show neuronal storage of **GM2 gangliosides**, not Gaucher cells. *Incorrect: Sphingomyelinase* - Deficiency of **sphingomyelinase** causes **Niemann-Pick disease**, characterized by hepatosplenomegaly, neurological involvement, and interstitial lung disease, but the storage cells (foam cells) have a **foamy appearance** due to sphingomyelin accumulation, not the "crinkled paper" appearance of Gaucher cells. - While there is organomegaly, the distinct **histological features** in the image rule out Niemann-Pick disease. *Incorrect: Alpha 1,4-glucosidase* - Deficiency of **alpha 1,4-glucosidase** (acid maltase) causes **Pompe disease** (Glycogen Storage Disease Type II), which primarily affects muscle and liver with **glycogen accumulation**. - Pompe disease does not typically present with the same type of **bone pain** or the characteristic **Gaucher cells** seen in the image. [Practice more Biochemistry PYQs on OnCourse]

Q: A newborn presented with chest retractions, dyspnea, and lethargy. The pediatrician diagnosed the baby with respiratory distress syndrome. This occurs due to the deficiency of:

Lecithin. ***Lecithin*** - **Respiratory distress syndrome (RDS)** in newborns is primarily caused by a deficiency of pulmonary **surfactant**. - **Lecithin (phosphatidylcholine)**, specifically in its dipalmitoyl form (**dipalmitoylphosphatidylcholine or DPPC**), is the main active component of surfactant, constituting ~40-50% of surfactant lipids. - DPPC is crucial for reducing surface tension in the alveoli and preventing their collapse during expiration. - This is the **primary biochemical deficiency** in neonatal RDS. *Dipalmitoyl inositol* - **Inositol** is a sugar alcohol involved in various cellular processes and is present in surfactant as phosphatidylinositol, but it is not a primary functional component. - Deficiency of this compound does not directly lead to **respiratory distress syndrome**. *Dipalmitoylphosphatidylethanolamine* - **Phosphatidylethanolamine (PE)** is a phospholipid found in cell membranes but is not the primary phospholipid responsible for surfactant function. - Note: This is PE, not PC (phosphatidylcholine). While PE is present in surfactant, its deficiency does not specifically cause **neonatal RDS**. *Sphingomyelin* - **Sphingomyelin** is a sphingolipid found in cell membranes and myelin sheaths, but it is not the critical component of pulmonary surfactant. - The **lecithin-to-sphingomyelin (L/S) ratio** is used to assess fetal lung maturity; an L/S ratio >2 indicates mature lungs capable of producing adequate surfactant. [Practice more Biochemistry PYQs on OnCourse]

Q: A patient presenting with bleeding gums and easy bruisability was diagnosed with scurvy. This condition results from a deficiency of which of the following?

Low vitamin C. ***Low vitamin C*** - **Scurvy** is directly caused by a severe deficiency of **vitamin C (ascorbic acid)**. - Vitamin C is a cofactor for **prolyl hydroxylase** and **lysyl hydroxylase**, enzymes essential for **collagen synthesis**. - Its deficiency leads to defective collagen formation, resulting in weakened connective tissues and fragile capillaries, explaining the bleeding gums and easy bruising. *Inhibition of vitamin K* - **Vitamin K** is crucial for the synthesis of **blood clotting factors** (II, VII, IX, X). - Its inhibition (e.g., by warfarin) would lead to bleeding disorders but does not explain the characteristic connective tissue problems (poor wound healing, perifollicular hemorrhages) seen in scurvy. *Increased collagen breakdown* - Conditions like **Ehlers-Danlos syndrome** involve abnormal collagen structure leading to tissue fragility. - Scurvy is characterized by a problem in the *synthesis* rather than the increased *breakdown* of collagen. *Defective collagen synthesis* - While this describes the **pathophysiological mechanism** of scurvy, it is not the answer to what the patient is *deficient in*. - The question asks for the underlying **nutritional deficiency**, which is **vitamin C**—the root cause that leads to defective collagen synthesis. [Practice more Biochemistry PYQs on OnCourse]

Q: An infant is brought by his parents with complaints that his urine turns black on standing. Which of the following metabolic disorders is likely?

Alkaptonuria. ***Alkaptonuria*** - **Alkaptonuria** is an autosomal recessive disorder characterized by a deficiency of **homogentisate 1,2-dioxygenase**, an enzyme involved in the metabolism of tyrosine. - The accumulation of **homogentisic acid** in tissues and urine causes the urine to turn black on standing due to oxidation. *Phenylketonuria* - **Phenylketonuria (PKU)** is caused by a deficiency of **phenylalanine hydroxylase**, leading to the accumulation of phenylalanine. - While it can manifest with intellectual disability and neurological symptoms, it does not typically cause the urine to turn black. *Homocystinuria* - **Homocystinuria** is a disorder of methionine metabolism, typically due to a deficiency of **cystathionine beta-synthase**. - It is characterized by intellectual disability, skeletal abnormalities, and lens dislocation, but not black urine. *Maple syrup urine disease* - **Maple syrup urine disease (MSUD)** results from a deficiency of **branched-chain alpha-keto acid dehydrogenase complex**, leading to the accumulation of branched-chain amino acids. - The distinguishing feature is urine that smells like maple syrup, not turning black. [Practice more Biochemistry PYQs on OnCourse]

Question 1

A 45-year-old male patient presents to the emergency department with severe pain and swelling in the big toe joint. He has a history of recurrent joint pain and dietary indiscretion. A specimen from the affected joint is subjected to a test that produces a purple color reaction. What is the test being performed?

Accepted Answer

Murexide test for uric acid detection

Answer

Florence test for choline compounds

Answer

Teichmann test for blood

Answer

Acid phosphatase test for prostate

Question 2

A child presents with bone pain and hepatosplenomegaly, indicative of Gaucher's disease. A trephine biopsy and aspirate show the following finding. Which of the following is the most likely enzyme deficient in this condition?

Accepted Answer

Glucocerebrosidase

Answer

Hexosaminidase

Answer

Sphingomyelinase

Answer

Alpha 1,4-glucosidase

Question 3

A newborn presented with chest retractions, dyspnea, and lethargy. The pediatrician diagnosed the baby with respiratory distress syndrome. This occurs due to the deficiency of:

Accepted Answer

Lecithin

Answer

Dipalmitoyl inositol

Answer

Dipalmitoylphosphatidylethanolamine

Answer

Sphingomyelin

Question 4

A patient presenting with bleeding gums and easy bruisability was diagnosed with scurvy. This condition results from a deficiency of which of the following?

Accepted Answer

Low vitamin C

Answer

Inhibition of vitamin K

Answer

Increased collagen breakdown

Answer

Defective collagen synthesis

Question 5

An infant is brought by his parents with complaints that his urine turns black on standing.    Which of the following metabolic disorders is likely?

Accepted Answer

Alkaptonuria

Answer

Phenylketonuria

Answer

Homocystinuria

Answer

Maple syrup urine disease

Question 6

A family consumes only polished rice. Which of the following combinations of vitamin deficiency and enzymatic defect will be present in this family?

Accepted Answer

Thiamine-transketolase

Answer

Riboflavin-glutathione reductase

Answer

Thiamine-transaminase

Answer

Riboflavin-transketolase

Question 7

Enzyme activated by decrease in Insulin: glucagon ratio:

Accepted Answer

Glucose 6 phosphatase

Answer

PFK

Answer

Glucokinase

Answer

Hexokinase

NEET-PG 2023 — Biochemistry