NEET-PG 2020 - Biochemistry PYQs Practice Questions

Q: Addition of which Amino Acid will increase UV absorption

Tryptophan. ***Tryptophan*** - **Tryptophan** contains an **indole ring** with a conjugated pi system responsible for strong **UV light absorption** at approximately **280 nm**. - Its unique aromatic structure allows it to absorb UV light, making it a key amino acid for protein quantification using **spectrophotometry**. *Leucine* - **Leucine** is an **aliphatic amino acid** with a non-polar side chain and lacks chromophores. - It does not significantly absorb UV light in the typical range used for protein analysis. *Proline* - **Proline** is an **imino acid** with a unique cyclic structure, but it lacks aromatic rings or conjugated double bonds. - It does not absorb UV light significantly at wavelengths above 230 nm. *Arginine* - **Arginine** is a **basic amino acid** with a guanidinium group, but this functional group does not contribute to UV absorption in the 280 nm range. - Its presence does not enhance the UV absorbance of proteins. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following is the richest source of vitamin B12?

Meat. ***Meat*** - **Meat** and other animal products are the primary natural dietary sources of **vitamin B12** (cobalamin). - This is because vitamin B12 is synthesized by bacteria and accumulates in animal tissues. *Green leafy vegetables* - **Green leafy vegetables** are excellent sources of many vitamins and minerals, such as **folate** and **vitamin K**, but they do not contain vitamin B12. - Vitamin B12 is essentially absent in plant-based foods unless they are fortified or contaminated. *Corn oil* - **Corn oil** is a vegetable oil primarily composed of fats and is a source of **vitamin E** and fatty acids, but it does not contain vitamin B12. - Oils derived from plants lack intrinsic vitamin B12 content. *Sunflower oil* - Similar to corn oil, **sunflower oil** is a plant-based oil rich in **vitamin E** and unsaturated fatty acids, but it contains **no vitamin B12**. - Plant oils are not a source of vitamin B12, which is almost exclusively found in animal products. [Practice more Biochemistry PYQs on OnCourse]

Q: Why is blood stored in citrate-phosphate-dextrose considered more beneficial for hypoxic patients compared to blood stored in acidic-citrate-dextrose?

The fall in 2,3-DPG is less.. ***The fall in 2,3-DPG is less.*** * **Citrate-phosphate-dextrose (CPD)** better preserves levels of **2,3-bisphosphoglycerate (2,3-DPG)** in stored red blood cells. * Higher 2,3-DPG levels are crucial for **oxygen unloading** from hemoglobin in tissues, which is particularly beneficial for hypoxic patients who need efficient oxygen delivery. *It has a higher pH level than acidic-citrate-dextrose.* * While CPD does maintain a **less acidic pH** than acid-citrate-dextrose (ACD), which is generally favorable for red blood cell viability, the most direct benefit for hypoxic patients relates to 2,3-DPG. * The slightly higher pH indirectly contributes to better 2,3-DPG preservation but isn't the primary reason for improved oxygen delivery. *It is more effective in oxygen delivery.* * While the *consequence* of using CPD is **more effective oxygen delivery** due to better 2,3-DPG preservation, this option describes the outcome rather than the underlying mechanism compared to the more specific answer regarding 2,3-DPG. * The increased efficacy in oxygen delivery is directly attributable to the preserved 2,3-DPG levels. *It has a longer shelf life than acidic-citrate-dextrose.* * The storage solutions primarily impact red blood cell viability and function, but the **shelf life** (typically 21-35 days depending on the anticoagulant/preservative) is generally determined by other factors, including the additive solutions used with the anticoagulant. * While CPD improves red blood cell quality, the primary advantage for hypoxic patients specifically lies in oxygen affinity rather than overall storage duration. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following statements regarding Huntington’s chorea is true?

It is a trinucleotide repeat expansion type of disorder. ***It is a trinucleotide repeat expansion type of disorder*** - Huntington's chorea is caused by an expansion of a **CAG trinucleotide repeat** in the **huntingtin gene (HTT)**. - This expansion leads to a misfolded protein and an **autosomal dominant** neurodegenerative disorder [1]. *There is a loss of function type of mutation.* - Huntington's chorea is primarily a **gain-of-function** mutation, where the expanded polyglutamine tract in the huntingtin protein leads to **toxic protein aggregation** and neuronal dysfunction. - While there might be some aspects of altered protein function, the core pathology is attributed to the **toxic effects** of the abnormal protein rather than a simple loss of its original function [1]. *It is an autosomal recessive disorder.* - Huntington's chorea is an **autosomal dominant** disorder, meaning only one copy of the mutated gene is sufficient to cause the disease. - Each child of an affected parent has a **50% chance** of inheriting the disease. *Increased number of CAA repeats.* - Huntington's chorea is characterized by an increased number of **CAG trinucleotide repeats**, not CAA repeats. - The expansion of these CAG repeats beyond a certain threshold (typically >35-40 repeats) in the huntingtin gene is directly responsible for the disease. [Practice more Biochemistry PYQs on OnCourse]

Question 1

Addition of which Amino Acid will increase UV absorption

Accepted Answer

Tryptophan

Answer

Leucine

Answer

Proline

Answer

Arginine

Question 2

Which of the following is the richest source of vitamin B12?

Accepted Answer

Meat

Answer

Green leafy vegetables

Answer

Corn oil

Answer

Sunflower oil

Question 3

Which of the following statements about protein structures is most accurate?

Accepted Answer

The sequence of amino acids determines the secondary and tertiary structures of proteins.

Answer

Secondary structure is stabilized by hydrogen bonds.

Answer

Denaturation primarily affects secondary and tertiary structures, leaving the primary structure intact.

Answer

The three-dimensional structure of a protein is referred to as its tertiary structure.

Question 4

Why is blood stored in citrate-phosphate-dextrose considered more beneficial for hypoxic patients compared to blood stored in acidic-citrate-dextrose?

Accepted Answer

The fall in 2,3-DPG is less.

Answer

It has a higher pH level than acidic-citrate-dextrose.

Answer

It is more effective in oxygen delivery.

Answer

It has a longer shelf life than acidic-citrate-dextrose.

Question 5

Which of the following statements regarding Huntington’s chorea is true?

Accepted Answer

It is a trinucleotide repeat expansion type of disorder

Answer

There is a loss of function type of mutation.

Answer

It is an autosomal recessive disorder.

Answer

Increased number of CAA repeats.

Question 6

30 years old came with complaints of easy fatigability, exertional dyspnea, and weight loss. She also complains of frequent falls. physical examination revealed there was a bilateral decrease in vibration sense. Her hemoglobin levels were 8.2g%. She was treated with folate. Her anemia improved but neurological symptoms worsened. Which of the following is the most probable reason for her condition?

Accepted Answer

Folate therapy caused rapid use of Vit B12 stores aggravating symptoms

Answer

Vitamin B6 deficiency unmasked by folate treatment.

Answer

Impaired folate metabolism in the central nervous system.

Answer

Malabsorption of folate due to gastrointestinal issues.

Question 7

Proteoglycan present in the glomerular basement membrane is?

Accepted Answer

Heparan sulfate

Answer

Keratan sulfate 1

Answer

Keratan sulfate 2

Answer

Chondroitin sulfate

Question 8

Which pigment is responsible for the greenish-black color of neonatal stool?

Accepted Answer

Biliverdin

Answer

Urochrome

Answer

Stercobilin

Answer

Bilirubin (yellow pigment)

Question 9

Ochronosis is due to the accumulation of?

Accepted Answer

Homogentisic acid

Answer

Alkapton

Answer

Xanthurenate

Answer

Glyoxylate

Question 10

Which absorbs least water?

Accepted Answer

Cellulose

Answer

Mucilage

Answer

Pectin

Answer

Gums

NEET-PG 2020 — Biochemistry