NEET-PG 2023 - Biochemistry PYQs Practice Questions

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

Thiamine-transketolase. ***Thiamine-transketolase*** - Consumption of **polished rice** is a classic cause of **thiamine (vitamin B1) deficiency** because the polishing process removes the outer layers of the grain where thiamine is abundant. - **Transketolase** is a key enzyme in the **pentose phosphate pathway** that requires thiamine pyrophosphate (TPP) as a cofactor, making its activity a reliable indicator of thiamine status. *Riboflavin-glutathione reductase* - **Glutathione reductase** activity is indeed used to assess **riboflavin (vitamin B2) status**, as it requires FAD (a derivative of riboflavin) as a cofactor. - However, **riboflavin deficiency** is not characteristically associated with consumption of polished rice. *Thiamine-transaminase* - While this option correctly identifies **thiamine**, the associated enzyme, **transaminase**, is incorrect in this context. - **Transaminases** are primarily dependent on **pyridoxal phosphate (vitamin B6)** as a cofactor, not thiamine. *Riboflavin-transketolase* - This option incorrectly combines **riboflavin deficiency** with the enzyme **transketolase**. - As mentioned, **transketolase** activity is specifically used to assess **thiamine status**, not riboflavin status. [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 chronic alcoholic patient presented to the casualty with confusion, ataxia, and painful eye movements. What vitamin deficiency is commonly associated with these symptoms?

Thiamine (Vitamin B1) deficiency. ***Thiamine (Vitamin B1) deficiency*** - The constellation of **confusion**, **ataxia**, and **ophthalmoplegia** (often presenting as painful eye movements) in a chronic alcoholic patient is highly characteristic of **Wernicke encephalopathy**, which results from thiamine deficiency [1]. - Chronic alcohol abuse severely impairs the **absorption**, **utilization**, and **storage** of thiamine, making this population particularly vulnerable to deficiency [1]. *Hypocalcemia* - Symptoms of hypocalcemia typically include **tetany**, **muscle cramps**, **paresthesias**, and in severe cases, seizures or cardiac arrhythmias, which are not described here. - While chronic alcoholism can affect calcium metabolism, hypocalcemia does not primarily manifest with the neurological triad observed. *Subacute combined degeneration (Vitamin B12 deficiency)* - This condition primarily affects the **dorsal columns** and **corticospinal tracts** of the spinal cord, leading to ataxia, paresthesias, and weakness, but typically does not cause acute confusion or painful eye movements. - While alcohol abuse can also be associated with B12 deficiency, the presented symptoms are not classic for subacute combined degeneration. *Pellagra (Niacin deficiency)* - Pellagra is characterized by the "3 Ds": **dermatitis**, **diarrhea**, and **dementia** (which is a progressive cognitive decline rather than acute confusion). - The presence of ataxia and painful eye movements is not a primary feature of niacin deficiency. [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]

Question 1

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 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 chronic alcoholic patient presented to the casualty with confusion, ataxia, and painful eye movements. What vitamin deficiency is commonly associated with these symptoms?

Accepted Answer

Thiamine (Vitamin B1) deficiency

Answer

Hypocalcemia

Answer

Subacute combined degeneration (Vitamin B12 deficiency)

Answer

Pellagra (Niacin deficiency)

Question 5

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 6

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 7

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 8

Which vitamin deficiency is most commonly associated with rickets in children?

Accepted Answer

Vitamin D

Answer

Vitamin A

Answer

Vitamin C

Answer

Vitamin K

Question 9

Enzyme activated by decrease in Insulin: glucagon ratio:

Accepted Answer

Glucose 6 phosphatase

Answer

PFK

Answer

Glucokinase

Answer

Hexokinase

NEET-PG 2023 — Biochemistry