INI-CET 2023 - Biochemistry PYQs Practice Questions

Q: Pompe disease is seen due to deficiency of?

Lysosomal acid alpha glucosidase. ***Lysosomal acid alpha glucosidase*** - **Pompe disease**, also known as **glycogen storage disease type II**, is caused by the deficiency of **acid alpha-glucosidase (GAA)**, a lysosomal enzyme. - This deficiency leads to the accumulation of **glycogen** within lysosomes in various tissues, particularly muscle, liver, and heart, causing muscle weakness and cardiomegaly. *β-galactocerebrosidase* - Deficiency of **β-galactocerebrosidase** is associated with **Krabbe disease** (globoid cell leukodystrophy). - Krabbe disease involves the buildup of **galactocerebroside**, leading to progressive destruction of the myelin sheath in the central and peripheral nervous systems. *β-glucocerebrosidase* - Deficiency in **β-glucocerebrosidase** causes **Gaucher disease**, the most common lysosomal storage disorder. - This results in the accumulation of **glucocerebroside** in macrophages, leading to hepatosplenomegaly, bone pain, and neurologic symptoms in some forms. *β-hexosaminidase-A* - Deficiency of **β-hexosaminidase-A** is the underlying cause of **Tay-Sachs disease**. - Tay-Sachs disease is characterized by the accumulation of **GM2 gangliosides** in neurons, leading to progressive neurodegeneration, developmental delay, and a characteristic cherry-red spot in the retina. [Practice more Biochemistry PYQs on OnCourse]

Q: Xanthurenic aciduria is seen in which vitamin deficiency?

Vitamin B6. ***Vitamin B6*** - **Xanthurenic aciduria** is a classic sign of **Vitamin B6 (pyridoxine) deficiency** because B6 is a crucial coenzyme for **kynureninase**, an enzyme in the **tryptophan metabolic pathway**. - Without sufficient B6, tryptophan cannot be properly metabolized, leading to the accumulation and excretion of xanthurenic acid. *Vitamin B5* - **Vitamin B5 (pantothenic acid)** is a precursor to **coenzyme A (CoA)**, essential for fatty acid metabolism and the **Krebs cycle**. - Its deficiency is associated with symptoms like paresthesia and fatigue, not xanthurenic aciduria. *Vitamin B12* - **Vitamin B12 (cobalamin)** is critical for DNA synthesis and the formation of **red blood cells**, and its deficiency causes **megaloblastic anemia** and neurological symptoms. - It plays no direct role in the tryptophan-kynurenine pathway, so its deficiency does not lead to xanthurenic aciduria. *Vitamin B7* - **Vitamin B7 (biotin)** acts as a coenzyme in **carboxylase reactions**, involved in fatty acid synthesis, gluconeogenesis, and amino acid metabolism. - Deficiency can cause dermatitis, hair loss, and neurological issues, but it is not linked to xanthurenic acid accumulation. [Practice more Biochemistry PYQs on OnCourse]

Q: BARTH syndrome is caused by deficiency of?

Cardiolipin. ***Cardiolipin*** - **BARTH syndrome** is a rare, X-linked genetic disorder caused by mutations in the **TAZ gene**, which encodes for the enzyme **tafazzin**. - **Tafazzin** is crucial for the remodeling of **cardiolipin**, a phospholipid essential for mitochondrial membrane integrity and function. Deficiency of properly remodeled (mature) cardiolipin leads to the characteristic cardiomyopathy, skeletal myopathy, neutropenia, and growth delay seen in BARTH syndrome. *Glycolipids* - **Glycolipids** are lipids with a carbohydrate attached, important for cell recognition and signaling. - Their deficiency or abnormal metabolism is associated with conditions like **glycosphingolipidoses** (e.g., Gaucher disease, Fabry disease), not BARTH syndrome. *Sphingomyelin* - **Sphingomyelin** is a type of sphingolipid found in animal cell membranes, particularly in the myelin sheath. - Its deficiency or accumulation is linked to **Niemann-Pick disease**, which presents with hepatosplenomegaly and neurodegeneration, distinct from BARTH syndrome. *Cerebroside* - **Cerebrosides** are a type of glycosphingolipid found in the myelin sheath and nerve cell membranes. - Disorders involving cerebroside metabolism include **Krabbe disease** (globoid cell leukodystrophy) and **Gaucher disease**, which are pathologically distinct from BARTH syndrome. [Practice more Biochemistry PYQs on OnCourse]

Q: DNA sequence is determined by?

Sanger sequencing. ***Correct: Sanger sequencing*** - **Sanger sequencing** (chain-termination method) is the gold standard technique used to determine the exact order of nucleotides within a DNA molecule - It uses dideoxynucleotides (ddNTPs) to terminate DNA strand elongation at specific bases, producing fragments of varying lengths - These fragments are separated by capillary electrophoresis and the sequence is read based on the terminal fluorescent label - Directly determines DNA sequence with high accuracy *Incorrect: PCR* - **Polymerase Chain Reaction (PCR)** amplifies specific DNA segments to create millions of copies - It does NOT determine the sequence itself - it only makes copies of DNA - PCR-amplified DNA can be used as a template for subsequent sequencing, but PCR itself doesn't reveal sequence information *Incorrect: FISH* - **Fluorescence in situ hybridization (FISH)** detects and localizes specific DNA sequences on chromosomes - Used for chromosomal mapping and detecting chromosomal abnormalities - Does not determine the nucleotide sequence *Incorrect: Gel electrophoresis* - Separates DNA fragments based on size and charge - Used to analyze DNA but cannot determine the specific nucleotide sequence - Useful for visualizing DNA after amplification or restriction digestion [Practice more Biochemistry PYQs on OnCourse]

Q: Liver produces ketones but cannot use it due to the deficiency of which of the following enzyme?

Thiophorase. ***Thiophorase*** - The liver lacks **thiophorase (succinyl-CoA:3-ketoacid CoA transferase)**, which is crucial for converting **acetoacetate** to **acetoacetyl-CoA**. - This enzyme deficiency prevents the liver from utilizing ketones as an energy source, even though it is a primary site for their production. *Alkaline phosphatase* - **Alkaline phosphatase** is a non-specific enzyme found in various tissues, including bone, liver, and intestine. - Its primary role is to **hydrolyze phosphate esters**, and it is not directly involved in ketone metabolism. *Alanine transaminase* - **Alanine transaminase (ALT)** is a liver enzyme primarily involved in **amino acid metabolism**, specifically in the transfer of an amino group from alanine to α-ketoglutarate. - It plays no direct role in the synthesis or utilization of ketone bodies. *Thiolase* - **Thiolase** is an enzyme involved in both the synthesis and breakdown of ketone bodies. - It converts **two acetyl-CoA molecules into acetoacetyl-CoA** during ketogenesis and also cleaves acetoacetyl-CoA into two acetyl-CoA molecules during ketolysis in extrahepatic tissues. [Practice more Biochemistry PYQs on OnCourse]

Question 1

Pompe disease is seen due to deficiency of?

Accepted Answer

Lysosomal acid alpha glucosidase

Answer

β-galactocerebrosidase

Answer

β-glucocerebrosidase

Answer

β-hexosaminidase-A

Question 2

Xanthurenic aciduria is seen in which vitamin deficiency?

Accepted Answer

Vitamin B6

Answer

Vitamin B5

Answer

Vitamin B12

Answer

Vitamin B7

Question 3

BARTH syndrome is caused by deficiency of?

Accepted Answer

Cardiolipin

Answer

Glycolipids

Answer

Sphingomyelin

Answer

Cerebroside

Question 4

DNA sequence is determined by?

Accepted Answer

Sanger sequencing

Answer

PCR

Answer

FISH

Answer

Gel electrophoresis

Question 5

Liver produces ketones but cannot use it due to the deficiency of which of the following enzyme?

Accepted Answer

Thiophorase

Answer

Alkaline phosphatase

Answer

Alanine transaminase

Answer

Thiolase

Question 6

A urine sample shows a maroon-colored ring at the interface of two layers after adding reagents. Identify the test:

Accepted Answer

Rothera's test

Answer

Benedict's test

Answer

Biuret test

Answer

Fehling's test

Question 7

What is the most common cause of pure gonadal dysgenesis with XY karyotype?

Accepted Answer

Point mutation

Answer

Deletion

Answer

Insertion

Answer

Translocation

Question 8

Which of the following is used to detect abnormal gene sequences EXCEPT?

Accepted Answer

Flow cytometry

Answer

RFLP analysis

Answer

Pyrosequencing

Answer

FISH

Question 9

Which membrane channel is mainly affected in Cystic fibrosis?

Accepted Answer

Chloride

Answer

Sodium

Answer

Calcium

Answer

Potassium

INI-CET 2023 — Biochemistry