NEET-PG 2022 - Biochemistry PYQs Practice Questions

Q: Which of the following statements is true regarding the telomerase theory of aging?

Decreased telomere length is associated with aging. ***Decreased telomere length is associated with aging*** - Telomeres are protective DNA-protein caps at chromosome ends that **shorten with each cell division** - Progressive telomere shortening triggers **cellular senescence** (Hayflick limit) and apoptosis - This mechanism directly contributes to aging and **age-related diseases** - The telomere theory of aging (Olovnikov hypothesis) states that telomere attrition is a primary driver of biological aging *Abnormal telomerase activation is associated with cancer* - **Telomerase is reactivated in ~85-90% of cancers**, enabling unlimited replicative potential - Normal adult somatic cells have low/absent telomerase activity - While telomerase can extend cellular lifespan, its aberrant activation leads to malignancy, not healthy aging *Telomere stability directly maintains chromosomal integrity* - Telomeres prevent chromosome degradation, end-to-end fusions, and DNA damage responses - This is a **protective function**, not the basis of the telomere theory of aging - The aging theory focuses on **consequences of telomere shortening**, not stability maintenance *Increased telomere length is associated with prolonged cellular lifespan* - Longer telomeres do correlate with younger biological age and extended replicative capacity - However, this describes the **inverse relationship** rather than the core aging theory - The telomere theory specifically explains aging through **progressive shortening**, not length extension [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following helps in the transport of fatty acids across the inner mitochondrial membrane?

Carnitine. ***Carnitine*** - **Carnitine** plays a crucial role in transporting long-chain fatty acids from the **cytosol** into the **mitochondrial matrix** for beta-oxidation. - It acts as a shuttling molecule, forming **acylcarnitine** which can cross the inner mitochondrial membrane via the **carnitine-acylcarnitine translocase**. *Acyl carrier protein* - **Acyl carrier protein (ACP)** is primarily involved in **fatty acid synthesis** in the cytoplasm, not in the transport of fatty acids into mitochondria for degradation. - It carries acyl groups during the elongation reactions of fatty acid synthesis. *Lecithin-cholesterol acyltransferase* - **Lecithin-cholesterol acyltransferase (LCAT)** is an enzyme found in plasma that catalyzes the formation of **cholesterol esters**, which are then transported by lipoproteins. - It is involved in **cholesterol metabolism** and reverse cholesterol transport, not in the mitochondrial transport of fatty acids. *Carnitine and albumin* - While **carnitine** is essential for mitochondrial fatty acid transport, **albumin** transports fatty acids in the blood plasma, from adipose tissue to other tissues. - Albumin does not transport fatty acids across the inner mitochondrial membrane; its role is extra-mitochondrial and related to systemic transport. [Practice more Biochemistry PYQs on OnCourse]

Q: An adolescent male patient presents to you with exercise intolerance. He gives a history of developing cramps on exertion. Which of the following enzyme deficiencies could be the cause?

Myophosphorylase. ***Myophosphorylase*** - A deficiency in **myophosphorylase** (McArdle's disease, Glycogen Storage Disease Type V) impairs muscle glycogen breakdown, leading to **exercise intolerance** and **muscle cramps** due to insufficient ATP production during exertion. - Patients often experience a "second wind" phenomenon where symptoms improve after resting, as free fatty acids become an alternative fuel source. *Hexokinase* - A deficiency in **hexokinase** would affect the first step of glycolysis, impacting glucose phosphorylation in all tissues, not specifically causing exercise-induced muscle cramps. - This deficiency is rare and typically presents with **hemolytic anemia** due to impaired erythrocyte metabolism. *Glucose-6-phosphatase* - A deficiency in **glucose-6-phosphatase** (Von Gierke's disease, Glycogen Storage Disease Type Ia) primarily affects the liver and kidneys, leading to **fasting hypoglycemia**, lactic acidosis, and hepatomegaly, not exercise intolerance. - Muscle glycogen metabolism is unaffected in this condition. *Hepatic glycogen phosphorylase* - A deficiency in **hepatic glycogen phosphorylase** (Hers' disease, Glycogen Storage Disease Type VI) mainly causes **hepatomegaly** and **mild hypoglycemia** because the liver cannot effectively mobilize its glycogen stores. - **Muscle glycogen metabolism** remains normal, so exercise intolerance and cramps are not characteristic symptoms. [Practice more Biochemistry PYQs on OnCourse]

Q: A young patient started to take a weight loss medication that acts by inhibiting fat absorption from food. After a few weeks, she developed easy bruising and increased menstrual bleeding. Deficiency of which of the following vitamins is responsible for her condition?

Vitamin K. ***Vitamin K*** - The patient is taking a **weight-loss medication** that **inhibits fat absorption**, leading to a deficiency in **fat-soluble vitamins**, including vitamin K. - **Vitamin K** is crucial for the synthesis of **coagulation factors** (II, VII, IX, X), and its deficiency leads to impaired clotting, manifesting as **easy bruising** and **increased menstrual bleeding**. *Vitamin E* - While vitamin E is a fat-soluble vitamin, its deficiency typically causes **neurological dysfunction** and **hemolytic anemia**, not bleeding diathesis. - Although malabsorption of vitamin E can occur with fat malabsorption, it does not directly explain the bleeding symptoms observed. *Vitamin B6* - Vitamin B6 is a **water-soluble vitamin**, so its absorption would not be directly affected by a medication inhibiting fat absorption. - Its deficiency can cause **neuropathy**, **dermatitis**, and **anemia**, but not increased bleeding. *Vitamin D* - Vitamin D is a **fat-soluble vitamin** whose deficiency is associated with **bone disorders** like **osteomalacia** and **rickets**, not bleeding. - While its absorption would be impacted by the medication, its deficiency would not cause easy bruising or increased menstrual bleeding. [Practice more Biochemistry PYQs on OnCourse]

Q: What is the term for a single mutation in a nucleotide base pair that results in a termination codon?

Nonsense mutation. ***Nonsense mutation*** - A **nonsense mutation** occurs when a single nucleotide base pair change leads to the formation of a **premature stop codon**, which results in a truncated and often non-functional protein. - The term "nonsense" refers to the fact that the new codon signals an early termination of protein synthesis. *Missense mutation* - A **missense mutation** involves a single nucleotide change that results in a codon coding for a **different amino acid**, potentially altering protein function but not necessarily terminating it. - This type of mutation can have varying effects on protein function, from benign to severe, depending on the amino acid substitution. *Termination mutation* - While a nonsense mutation does result in **premature termination**, "termination mutation" is not the standard or most precise scientific term used to describe this specific type of genetic alteration. - The more accurate and widely accepted terminology is **nonsense mutation** for a change leading to a stop codon. *Silent mutation* - A **silent mutation** is a type of point mutation that changes a single nucleotide, but does not change the amino acid sequence of the protein due to the **degeneracy of the genetic code**. - These mutations have **no observable effect** on the organism's phenotype as the protein produced remains unchanged. [Practice more Biochemistry PYQs on OnCourse]

Question 1

Which of the following statements is true regarding the telomerase theory of aging?

Accepted Answer

Decreased telomere length is associated with aging

Answer

Abnormal telomerase activation is associated with cancer

Answer

Telomere stability directly maintains chromosomal integrity

Answer

Increased telomere length is associated with prolonged cellular lifespan

Question 2

Which of the following helps in the transport of fatty acids across the inner mitochondrial membrane?

Accepted Answer

Carnitine

Answer

Acyl carrier protein

Answer

Lecithin-cholesterol acyltransferase

Answer

Carnitine and albumin

Question 3

An adolescent male patient presents to you with exercise intolerance. He gives a history of developing cramps on exertion. Which of the following enzyme deficiencies could be the cause?

Accepted Answer

Myophosphorylase

Answer

Hexokinase

Answer

Glucose-6-phosphatase

Answer

Hepatic glycogen phosphorylase

Question 4

A young patient started to take a weight loss medication that acts by inhibiting fat absorption from food. After a few weeks, she developed easy bruising and increased menstrual bleeding. Deficiency of which of the following vitamins is responsible for her condition?

Accepted Answer

Vitamin K

Answer

Vitamin E

Answer

Vitamin B6

Answer

Vitamin D

Question 5

What is the term for a single mutation in a nucleotide base pair that results in a termination codon?

Accepted Answer

Nonsense mutation

Answer

Missense mutation

Answer

Termination mutation

Answer

Silent mutation

Question 6

The electron transport chain is a series of redox reactions that result in ATP synthesis. Which of the following is a cytochrome complex IV inhibitor?

Accepted Answer

Cyanide

Answer

Carbon dioxide

Answer

Oligomycin

Answer

Ouabain

Question 7

Cancer cells preferentially utilize glycolysis for energy production even in the presence of adequate oxygen. What is this phenomenon called?

Accepted Answer

Warburg effect

Answer

Hypoxic adaptation

Answer

Anoxic survival

Answer

Oxygen-independent metabolism

Question 8

A patient with hemolytic anemia has a defect in the enzyme glucose-6-phosphate dehydrogenase. Which of the following pathways is directly affected by this defect?

Accepted Answer

Pentose phosphate pathway

Answer

Glycolysis

Answer

TCA cycle

Answer

Urea cycle

Question 9

A patient is diagnosed with scurvy. This condition is due to a deficiency in which vitamin?

Accepted Answer

Vitamin C

Answer

Vitamin A

Answer

Vitamin D

Answer

Vitamin E

NEET-PG 2022 — Biochemistry