UPSC-CMS 2009 - Biochemistry PYQs Practice Questions

Q: The milk of which of the following contains the least amount of calcium?

Human. ***Human*** - **Human breast milk** contains the lowest concentration of calcium compared to the milk of other mammals listed. - This is physiologically appropriate as infants absorb calcium very efficiently from human milk, and higher concentrations are not necessary. *Cow* - **Cow's milk** has a significantly higher calcium content than human milk, which is suitable for the rapid growth of calf bones. - The **calcium-to-phosphorus ratio** in cow's milk is also different, which can affect absorption and metabolism in infants. *Buffalo* - **Buffalo milk** generally has an even higher calcium content than cow's milk. - It is known for its **richness in nutrients** and higher fat and protein content, contributing to its denser consistency. *Goat* - **Goat's milk** has a calcium content that is higher than human milk, though often slightly less than cow's milk. - Its calcium is absorbed relatively well, but its overall composition is still very different from human milk, particularly in terms of **protein and micronutrient balance**. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following correctly describes gene therapy ?

Introduction of gene sequence into a cell. ***Introduction of gene sequence into a cell*** - **Gene therapy** fundamentally involves the **delivery of genetic material** (DNA or RNA) into a patient's cells to treat or prevent disease. - The goal is to correct a **genetic defect**, provide a new therapeutic function, or alter gene expression for a desired outcome. *Mapping and isolation of gene sequence* - While essential steps in understanding and preparing for gene therapy, **mapping and isolation** alone do not constitute the therapy itself. - These processes are preliminary research activities to identify the target gene and its location. *Synthesis of DNA probes with specific sequence* - **DNA probes** are short, single-stranded DNA or RNA sequences used to detect the presence of complementary nucleic acid sequences. - Their synthesis is a technique used in **molecular diagnostics** and research, not gene therapy, which aims to introduce functional genes. *Use of polymerase chain reaction technique* - **PCR** is a molecular biology technique used to amplify a specific segment of DNA, creating many copies. - It is a tool for **diagnosis**, research, and sometimes in the preparation of genetic material for therapy, but it is not gene therapy itself. [Practice more Biochemistry PYQs on OnCourse]

Q: Consider the following statements : 1. The deficiency of thiamine leads to the accumulation of pyruvic and lactic acids in the body. 2. Riboflavin deficiency impairs the optimal utilization of pyridoxine. Which of the statements given above is/are correct ?

Both 1 and 2. ***Both 1 and 2*** - **Statement 1 is correct**: Thiamine (vitamin B1) as **thiamine pyrophosphate (TPP)** is an essential coenzyme for the **pyruvate dehydrogenase complex** and **α-ketoglutarate dehydrogenase**. Deficiency blocks pyruvate conversion to acetyl-CoA, causing accumulation of **pyruvic acid** and its reduction product **lactic acid**, leading to metabolic acidosis seen in **beriberi** and **Wernicke-Korsakoff syndrome**. - **Statement 2 is correct**: Riboflavin (vitamin B2) as **FMN** serves as a cofactor for **pyridoxine 5'-phosphate oxidase**, the enzyme that converts pyridoxine 5'-phosphate and pyridoxamine 5'-phosphate to the active form **pyridoxal 5'-phosphate (PLP)**. Riboflavin deficiency impairs this conversion, leading to **functional vitamin B6 deficiency** even with adequate dietary pyridoxine intake. *1 only* - This option is incorrect because it ignores the well-established biochemical relationship between riboflavin and pyridoxine metabolism. Both statements are factually accurate. *2 only* - This option is incorrect because statement 1 is definitively correct. Thiamine deficiency is a classic cause of **pyruvic and lactic acid accumulation** due to impaired oxidative decarboxylation. *Neither 1 nor 2* - This option is incorrect as both statements are medically and biochemically accurate, reflecting established vitamin interdependencies and metabolic pathways. [Practice more Biochemistry PYQs on OnCourse]

Q: Which of the following fats has the highest concentration of saturated fatty acids ?

Coconut oil. ***Coconut oil*** - **Coconut oil** has the **highest concentration of saturated fatty acids** among common dietary fats, with approximately **82-92% of its total fatty acids being saturated**. - The predominant saturated fatty acid is **lauric acid (C12:0)**, which comprises roughly **45-50%** of its fatty acid profile. - This exceptionally high saturation contributes to its **solid consistency** at room temperature and its stability during cooking. *Butter* - **Butter** is a dairy product containing approximately **50-65% saturated fatty acids**, which is significantly less than coconut oil. - It contains a mix of short-chain, medium-chain, and long-chain saturated fats, along with **monounsaturated** and **polyunsaturated** fats, and **cholesterol**. *Margarine* - **Margarine** was traditionally made from **partially hydrogenated vegetable oils**, leading to high **trans fat** content and variable saturated fat levels. - Modern formulations use **non-hydrogenated or interesterified oils** to reduce trans fats, with saturated fat content varying widely (10-80%) depending on the source oils and processing methods. *Palm oil* - **Palm oil** contains approximately **49-52% saturated fatty acids**, primarily **palmitic acid (C16:0)**, which makes up about 44% of its total fat content. - While high in saturated fat compared to most vegetable oils, it contains substantially less saturated fat than **coconut oil**. [Practice more Biochemistry PYQs on OnCourse]

Question 1

The milk of which of the following contains the least amount of calcium?

Accepted Answer

Human

Answer

Cow

Answer

Buffalo

Answer

Goat

Question 2

Which of the following correctly describes gene therapy ?

Accepted Answer

Introduction of gene sequence into a cell

Answer

Mapping and isolation of gene sequence

Answer

Synthesis of DNA probes with specific sequence

Answer

Use of polymerase chain reaction technique

Question 3

Consider the following statements :

1. The deficiency of thiamine leads to the accumulation of pyruvic and lactic acids in the body.
2. Riboflavin deficiency impairs the optimal utilization of pyridoxine. Which of the statements given above is/are correct ?

Accepted Answer

Both 1 and 2

Answer

1 only

Answer

2 only

Answer

Neither 1 nor 2

Question 4

Which of the following fats has the highest concentration of saturated fatty acids ?

Accepted Answer

Coconut oil

Answer

Butter

Answer

Margarine

Answer

Palm oil

UPSC-CMS 2009 — Biochemistry