FMGE 2019 - Biochemistry PYQs Practice Questions

Q: Keshan's disease is due to deficiency of:

Selenium. **Selenium (Correct Answer)** - **Keshan disease** is an endemic cardiomyopathy characterized by multifocal myocyte necrosis, which has been directly linked to a severe dietary deficiency of **selenium**. - Selenium is an essential component of **glutathione peroxidase**, an enzyme critical for protecting cells against oxidative damage. - The disease is named after Keshan County in China where it was first identified in selenium-deficient regions. *Iron (Incorrect)* - **Iron deficiency** primarily leads to **anemia**, characterized by fatigue, pallor, and weakness due to insufficient hemoglobin production. - It does not directly cause the specific cardiomyopathy seen in Keshan disease. *Zinc (Incorrect)* - **Zinc deficiency** can cause a range of symptoms including impaired immune function, skin lesions (acrodermatitis enteropathica), hair loss, and growth retardation. - It is not associated with the cardiac manifestations of Keshan disease. *Copper (Incorrect)* - **Copper deficiency** can result in anemia, neutropenia, impaired immune function, and neurological dysfunction (Menkes disease). - While copper is important for various metalloenzymes, its deficiency does not cause Keshan disease. [Practice more Biochemistry PYQs on OnCourse]

Q: Protein content in cow's milk in comparison to human milk is?

Triple. ***Triple*** - The protein content in **cow's milk** is approximately **three times higher** than that found in **human milk**. - **Cow's milk** contains approximately **3.3 g/100 mL** of protein, while **human milk** contains about **1.0-1.3 g/100 mL**. - This higher protein load in cow's milk can be challenging for an infant's immature kidneys and digestion. - The predominant protein in cow's milk is **casein (80%)**, while human milk has more **whey proteins (60%)**. *Quadruple* - While cow's milk has significantly more protein than human milk, it is not **four times** the amount. - The exact ratio is closer to **three times (3:1)**, making quadruple an overestimation. *Double* - The protein content of cow's milk is **more than double** that of human milk. - Therefore, stating it is merely double **underestimates** the difference in protein concentration. *Same* - The protein content of **cow's milk and human milk are not the same**. - There are significant differences in both the **quantity** (3:1 ratio) and **type of proteins** (casein vs whey predominance). - These differences make each milk suited for different species' developmental needs. [Practice more Biochemistry PYQs on OnCourse]

Q: Zinc is cofactor of which enzyme?

Carbonic anhydrase. ***Carbonic anhydrase*** - **Zinc** is an essential cofactor for **carbonic anhydrase**, crucial for its enzymatic activity in catalyzing the reversible hydration of carbon dioxide. - This enzyme plays a vital role in processes like **pH regulation**, **carbon dioxide transport**, and **bicarbonate production** in various tissues. *Carboxylase* - Carboxylases typically require **biotin** as a cofactor for their activity, which involves the addition of a carboxyl group to a substrate. - Examples include **pyruvate carboxylase** and **acetyl-CoA carboxylase**, which are fundamental in metabolic pathways. *Kinase* - Kinases are enzymes that catalyze the transfer of a **phosphate group** from a high-energy donor molecule (like ATP) to a substrate. - Their activity often depends on cofactors like **magnesium (Mg2+)** or **manganese (Mn2+)**, not zinc. *Lysyl oxidase* - **Lysyl oxidase** is an enzyme that requires **copper** as a cofactor for its activity. - It plays a critical role in the **cross-linking of collagen and elastin**, essential for the integrity of connective tissues. [Practice more Biochemistry PYQs on OnCourse]

Q: All are cofactors for Dehydrogenase except:

SAM. ***SAM*** - **S-adenosylmethionine (SAM)** is a cofactor involved in **methyl group transfer reactions**, carried out by enzymes known as methyltransferases. - Dehydrogenase enzymes catalyze **redox reactions**, typically involving the transfer of hydride ions, and thus do not utilize SAM as a cofactor. *NADP* - **Nicotinamide adenine dinucleotide phosphate (NADP)** is a crucial coenzyme for many **dehydrogenase reactions**, particularly in **anabolic pathways** like fatty acid synthesis and the pentose phosphate pathway. - It acts as an **electron carrier**, accepting or donating hydride ions. *NAD* - **Nicotinamide adenine dinucleotide (NAD)** is a highly common coenzyme for numerous **dehydrogenase enzymes**, especially in **catabolic pathways** such as glycolysis, the Krebs cycle, and oxidative phosphorylation. - It functions as an **electron acceptor** or donor in redox reactions. *FAD* - **Flavin adenine dinucleotide (FAD)** is a coenzyme derived from **riboflavin (Vitamin B2)** and is associated with various dehydrogenase enzymes, particularly those involved in **electron transport** and fatty acid oxidation. - FAD can accept two hydrogen atoms (one hydride and one proton) to become FADH₂. [Practice more Biochemistry PYQs on OnCourse]

Q: Which structure of protein is not denatured after heating up to 100 degrees Celsius?

Primary. ***Primary*** - The **primary structure** refers to the specific linear sequence of **amino acids** forming the polypeptide chain, linked by **covalent peptide bonds**. - These strong **peptide bonds** are generally resistant to heat denaturation at 100°C, meaning the amino acid sequence remains intact. *Quaternary* - The **quaternary structure** involves the arrangement of multiple polypeptide subunits and is maintained by weaker interactions like **hydrophobic interactions**, hydrogen bonds, and salt bridges. - These interactions are highly susceptible to disruption by heat, causing the subunits to dissociate and the quaternary structure to be lost. *Tertiary* - The **tertiary structure** describes the three-dimensional folding of a single polypeptide chain, stabilized by various non-covalent interactions (e.g., hydrogen bonds, ionic bonds, hydrophobic interactions) and **disulfide bonds**. - Heat disrupts these weaker non-covalent interactions and can even break disulfide bonds, leading to the unfolding and loss of the specific 3D shape. *Secondary* - The **secondary structure** (e.g., **alpha-helices** and **beta-pleated sheets**) arises from hydrogen bonds between the backbone atoms of the polypeptide chain. - While peptide bonds remain intact, these vital **hydrogen bonds** are easily broken by heat, causing the unraveling of helices and sheets. [Practice more Biochemistry PYQs on OnCourse]

Question 1

Keshan's disease is due to deficiency of:

Accepted Answer

Selenium

Answer

Iron

Answer

Zinc

Answer

Copper

Question 2

Protein content in cow's milk in comparison to human milk is?

Accepted Answer

Triple

Answer

Quadruple

Answer

Double

Answer

Same

Question 3

Zinc is cofactor of which enzyme?

Accepted Answer

Carbonic anhydrase

Answer

Carboxylase

Answer

Kinase

Answer

Lysyl oxidase

Question 4

All are cofactors for Dehydrogenase except:

Accepted Answer

SAM

Answer

NADP

Answer

NAD

Answer

FAD

Question 5

Which structure of protein is not denatured after heating up to 100 degrees Celsius?

Accepted Answer

Primary

Answer

Quaternary

Answer

Tertiary

Answer

Secondary

Question 6

Most abundant amino acid found in collagen?

Accepted Answer

Glycine

Answer

Hydroxyproline

Answer

Proline

Answer

Lysine

Question 7

Which is a product of purine metabolism?

Accepted Answer

Uric acid

Answer

Xanthine

Answer

Beta alanine

Answer

Urea

Question 8

Melanin is derived from which amino acid?

Accepted Answer

Tyrosine

Answer

Phenylalanine

Answer

Alanine

Answer

Tryptophan

Question 9

Which bases are present in human DNA?

Accepted Answer

Adenine-guanine-cytosine-thymine

Answer

None of the above

Answer

Adenine-guanine-cytosine-uracil

Answer

Adenine-guanine-thiamine-uracil

Question 10

Type IV complex of ETC is inhibited by

Accepted Answer

Cyanide

Answer

Antimycin

Answer

Oligomycin

Answer

CO2

FMGE 2019 — Biochemistry