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

JAK-STAT pathway is seen in which of the following?

Accepted Answer

Leptin

Answer

Calcitonin

Answer

Aldosterone

Answer

Vasopressin

Question 9

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

Accepted Answer

Flow cytometry

Answer

RFLP analysis

Answer

Pyrosequencing

Answer

FISH

Question 10

Which membrane channel is mainly affected in Cystic fibrosis?

Accepted Answer

Chloride

Answer

Sodium

Answer

Calcium

Answer

Potassium

INI-CET 2023 — Biochemistry