INI-CET 2021 - Biochemistry PYQs Practice Questions

Q: Methyl-tetrahydrofolate (5-methyl-THF) gets accumulated in deficiency of which of the following?

Vitamin B12 (Cobalamin). ***Vitamin B12 (Cobalamin)*** - A deficiency in **Vitamin B12** (cobalamin) leads to the accumulation of **5-methyl-tetrahydrofolate (5-methyl-THF)** due to the **"folate trap"** hypothesis. - This occurs because B12 is a cofactor for **methionine synthase**, which converts 5-methyl-THF back to tetrahydrofolate (THF), a necessary step for DNA synthesis and other one-carbon metabolism reactions. - Without B12, folate remains trapped in the methyl form and cannot be utilized for other essential reactions. *Vitamin B2 (Riboflavin)* - **Vitamin B2** (riboflavin) is a precursor for **FAD** and **FMN**, essential coenzymes in various redox reactions in the electron transport chain and other metabolic pathways. - Its deficiency typically presents as **cheilosis**, glossitis, and angular stomatitis, but does not cause methyl-THF accumulation. *Vitamin B1 (Thiamine)* - **Vitamin B1** (thiamine) is a cofactor for enzymes like **pyruvate dehydrogenase** and **alpha-ketoglutarate dehydrogenase** in carbohydrate metabolism. - Its deficiency causes **Beriberi** (wet, dry, or Wernicke-Korsakoff syndrome), affecting the cardiovascular and nervous systems, but does not affect folate metabolism. *Vitamin B6 (Pyridoxine)* - **Vitamin B6** (pyridoxine) is a coenzyme for many metabolic reactions, particularly in amino acid metabolism and neurotransmitter synthesis. - Deficiency can lead to **sideroblastic anemia**, neurological symptoms, and dermatitis, but does not cause methyl-THF accumulation. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following molecular analysis methods is used to detect RNA?

RT-PCR. ***RT-PCR*** - **Reverse transcriptase polymerase chain reaction (RT-PCR)** is a molecular method that first converts **RNA into complementary DNA (cDNA)** using reverse transcriptase before amplification via PCR. - This technique is commonly used to detect and quantify specific **RNA sequences**, such as viral RNA or gene expression levels. *Western blot* - **Western blot** is a laboratory technique used to detect specific **proteins** in a sample. - It involves separating proteins by size using gel electrophoresis, transferring them to a membrane, and then detecting the target protein using specific antibodies. *G banding* - **G banding** is a cytogenetic technique used to produce a visible **karyotype** by staining condensed chromosomes. - This method is primarily used to detect large-scale structural changes in chromosomes, not to detect RNA. *Sanger's method* - **Sanger's method**, also known as **dideoxy sequencing**, is a DNA sequencing technique. - It is used to determine the exact order of **nucleotides within a DNA molecule**, not to detect RNA directly. [Practice more Biochemistry PYQs on OnCourse]

Q: Glycated hemoglobin (HbA1c) is best measured using?

Ion exchange chromatography. ***Ion exchange chromatography*** - This method separates hemoglobin variants based on their **charge differences** due to the glucose molecule attached to HbA1c. - It is a highly sensitive and specific method for quantifying HbA1c, widely used in clinical laboratories. *Isoelectric focusing* - This technique separates molecules based on their **isoelectric point (pI)**, the pH at which they have no net charge. - While it can differentiate some hemoglobin variants, it is generally **less efficient and more complex** for routine HbA1c measurement compared to ion exchange chromatography. *Affinity chromatography* - This method separates molecules based on their **specific binding affinity** to a ligand immobilized on a stationary phase. - While it has been explored for HbA1c measurement, it is **not the most commonly used** or preferred method due to potential interferences and cost compared to ion exchange chromatography. *Electrophoresis* - This technique separates molecules based on their **charge and size** in an electric field. - While it can separate major hemoglobin variants, it has **lower resolution and accuracy** for routine HbA1c quantification compared to more specialized chromatographic methods, making it less ideal for precise measurement. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following options is false in a patient with advanced liver disease?

Increased oxidative decarboxylation of alpha-ketoglutarate. ***Increased oxidative decarboxylation of alpha-ketoglutarate*** - In advanced liver disease, **hepatic encephalopathy** is a common complication due to the liver's inability to detoxify **ammonia**. - Alpha-ketoglutarate is crucial for detoxifying ammonia into glutamate and then glutamine, processes that involve reductive amination and **ATP consumption**, not increased oxidative decarboxylation. *Decreased ATP synthesis* - Advanced liver disease impairs various metabolic functions, including those of the **mitochondria**, leading to decreased ATP production. - This reduction in **energy reserves** affects numerous cellular processes and organ functions. *Hyperammonemia* - The liver is responsible for detoxifying **ammonia** into urea via the **urea cycle**. - In advanced liver disease, the impaired function of the liver leads to a buildup of ammonia in the blood, resulting in **hyperammonemia**. *Increased synthesis of glutamine and glutamate from alpha-ketoglutarate* - In the brain, when the liver fails to detoxify ammonia, **astrocytes** attempt to convert excess ammonia into **glutamine** using **alpha-ketoglutarate**. - This process is a compensatory mechanism to reduce ammonia toxicity, but it depletes alpha-ketoglutarate, which is a key intermediate in the **Krebs cycle**, leading to **cerebral energy deficits**. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following is not a substrate for glucose formation?

Acetyl coenzyme A. ***Acetyl coenzyme A*** - **Acetyl CoA** cannot be converted to glucose because the two carbons from the acetyl group are lost as carbon dioxide in the **Krebs cycle**, making a net synthesis of glucose impossible. - The irreversible nature of the **pyruvate dehydrogenase complex** prevents the conversion of Acetyl CoA back to **pyruvate**, which is a crucial step for gluconeogenesis. *Lactate* - **Lactate** is a major substrate for gluconeogenesis, particularly during exercise and fasting, via the **Cori cycle**. - **Lactate dehydrogenase** converts lactate to **pyruvate**, which can then enter the gluconeogenic pathway. *Glycerol* - **Glycerol**, derived from triglyceride breakdown, enters gluconeogenesis by being converted to **glycerol-3-phosphate** and then to **dihydroxyacetone phosphate (DHAP)**. - DHAP is an intermediate in glycolysis and gluconeogenesis, allowing for its conversion to glucose. *Alanine* - **Alanine** is a **glucogenic amino acid** that can be transaminated to **pyruvate**. - **Pyruvate** can then proceed through the gluconeogenic pathway to synthesize glucose, especially during prolonged fasting. [Practice more Biochemistry PYQs on OnCourse]

Question 1

Methyl-tetrahydrofolate (5-methyl-THF) gets accumulated in deficiency of which of the following?

Accepted Answer

Vitamin B12 (Cobalamin)

Answer

Vitamin B2 (Riboflavin)

Answer

Vitamin B1 (Thiamine)

Answer

Vitamin B6 (Pyridoxine)

Question 2

Which of the following molecular analysis methods is used to detect RNA?

Accepted Answer

RT-PCR

Answer

Western blot

Answer

G banding

Answer

Sanger's method

Question 3

Glycated hemoglobin (HbA1c) is best measured using?

Accepted Answer

Ion exchange chromatography

Answer

Isoelectric focusing

Answer

Affinity chromatography

Answer

Electrophoresis

Question 4

Which of the following options is false in a patient with advanced liver disease?

Accepted Answer

Increased oxidative decarboxylation of alpha-ketoglutarate

Answer

Decreased ATP synthesis

Answer

Hyperammonemia

Answer

Increased synthesis of glutamine and glutamate from alpha-ketoglutarate

Question 5

Which of the following is not a substrate for glucose formation?

Accepted Answer

Acetyl coenzyme A

Answer

Lactate

Answer

Glycerol

Answer

Alanine

Question 6

What is the repair mechanism associated with CRISPR-cas9?

Accepted Answer

Non-homologous end joining

Answer

Mismatch repair

Answer

Nucleotide excision repair

Answer

Base excision repair

Question 7

Which of the following is not amphipathic?

Accepted Answer

Triglycerides

Answer

Sphingolipids

Answer

Glycolipids

Answer

Phosphoglycerol

Question 8

Beta hCG is structurally similar to which biochemical moiety?

Accepted Answer

LH

Answer

Oxytocin

Answer

FSH

Answer

ACTH

Question 9

miRNA binds to which part of the mRNA to inhibit translation?

Accepted Answer

3'UTR

Answer

Gene promoter

Answer

Gene body

Answer

5'UTR

Question 10

Which of the following methods cannot be used to precipitate proteins?

Accepted Answer

Moving pH away from isoelectric pH

Answer

Add alcohol and acetone

Answer

Using heavy metal ions

Answer

Adding trichloroacetic acid

INI-CET 2021 — Biochemistry