UPSC-CMS 2009 — Biochemistry

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: Among the following, which has the highest quantity of retinol (Vitamin A) activity per 100 g of fruit?

Ripe Mango. ***Ripe Mango*** - **Ripe mangoes** are an excellent source of **beta-carotene**, which the body converts into **retinol (Vitamin A)**. - They contain approximately **1,262 µg retinol activity equivalents (RAE)** per 100 g, which is significantly higher than the other options listed. - While fruits contain provitamin A carotenoids rather than preformed retinol, mangoes provide the highest **Vitamin A activity** among these choices. *Papaya* - While papaya does contain **beta-carotene**, its concentration is much lower (approximately **47 µg RAE/100 g**). - It is a good source of Vitamin C and other antioxidants, but not the leading source of Vitamin A among these fruits. *Tomato* - Tomatoes are rich in **lycopene**, another carotenoid, but it is not converted to **retinol** as beta-carotene is. - They have low overall **Vitamin A activity** (approximately **42 µg RAE/100 g**) compared to mangoes. *Orange* - Oranges are primarily known for their high content of **Vitamin C** and are poor sources of **Vitamin A**. - Their Vitamin A activity is minimal (approximately **11 µg RAE/100 g**), with primary carotenoids being **beta-cryptoxanthin** and **zeaxanthin**, which contribute less to Vitamin A activity. [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: The law stating that "the relative frequencies of each gene allele tend to remain constant from generation to generation" is known as

Hardy-Weinberg Law. ***Hardy-Weinberg Law*** - The **Hardy-Weinberg principle** states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. - This law provides a baseline for understanding how populations evolve by identifying the conditions under which evolution *does not* occur. *Lamarck's Law* - **Lamarck's theory of inheritance of acquired characteristics** suggested that traits acquired during an organism's lifetime could be passed on to offspring. - This concept is largely disproven and not relevant to allele frequency constancy across generations. *David-Morgan's Law* - This is not a recognized law in genetics. There was a prominent geneticist named **Thomas Hunt Morgan**, whose work focused on fruit flies and established the **chromosome theory of inheritance** and concepts like linkage and crossing over. - While significant to genetics, his work does not describe the constancy of allele frequencies in a population. *Mendel's Law* - **Mendel's Laws of Inheritance** (segregation and independent assortment) describe how traits are passed from parents to offspring through the inheritance of discrete units (genes). - While fundamental to explaining inheritance, they do not directly state that allele frequencies remain constant in a population across generations under specific conditions, as the Hardy-Weinberg law does. [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]

6 Previous Year Questions with Answers & Explanations

Questions

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

Among the following, which has the highest quantity of retinol (Vitamin A) activity per 100 g of fruit?

Which of the following correctly describes gene therapy ?

The law stating that "the relative frequencies of each gene allele tend to remain constant from generation to generation" is known as

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 ?

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

UPSC-CMS 2009 - Biochemistry UPSC-CMS Practice Questions and MCQs

Question 1: The milk of which of the following contains the least amount of calcium?

A. Cow
B. Buffalo
C. Human (Correct Answer)
D. Goat

Explanation: ***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**.

Question 2: Among the following, which has the highest quantity of retinol (Vitamin A) activity per 100 g of fruit?

A. Papaya
B. Tomato
C. Ripe Mango (Correct Answer)
D. Orange

Explanation: ***Ripe Mango*** - **Ripe mangoes** are an excellent source of **beta-carotene**, which the body converts into **retinol (Vitamin A)**. - They contain approximately **1,262 µg retinol activity equivalents (RAE)** per 100 g, which is significantly higher than the other options listed. - While fruits contain provitamin A carotenoids rather than preformed retinol, mangoes provide the highest **Vitamin A activity** among these choices. *Papaya* - While papaya does contain **beta-carotene**, its concentration is much lower (approximately **47 µg RAE/100 g**). - It is a good source of Vitamin C and other antioxidants, but not the leading source of Vitamin A among these fruits. *Tomato* - Tomatoes are rich in **lycopene**, another carotenoid, but it is not converted to **retinol** as beta-carotene is. - They have low overall **Vitamin A activity** (approximately **42 µg RAE/100 g**) compared to mangoes. *Orange* - Oranges are primarily known for their high content of **Vitamin C** and are poor sources of **Vitamin A**. - Their Vitamin A activity is minimal (approximately **11 µg RAE/100 g**), with primary carotenoids being **beta-cryptoxanthin** and **zeaxanthin**, which contribute less to Vitamin A activity.

Question 3: Which of the following correctly describes gene therapy ?

A. Mapping and isolation of gene sequence
B. Introduction of gene sequence into a cell (Correct Answer)
C. Synthesis of DNA probes with specific sequence
D. Use of polymerase chain reaction technique

Explanation: ***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.

Question 4: The law stating that "the relative frequencies of each gene allele tend to remain constant from generation to generation" is known as

A. Lamarck's Law
B. David-Morgan's Law
C. Mendel's Law
D. Hardy-Weinberg Law (Correct Answer)

Explanation: ***Hardy-Weinberg Law*** - The **Hardy-Weinberg principle** states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. - This law provides a baseline for understanding how populations evolve by identifying the conditions under which evolution *does not* occur. *Lamarck's Law* - **Lamarck's theory of inheritance of acquired characteristics** suggested that traits acquired during an organism's lifetime could be passed on to offspring. - This concept is largely disproven and not relevant to allele frequency constancy across generations. *David-Morgan's Law* - This is not a recognized law in genetics. There was a prominent geneticist named **Thomas Hunt Morgan**, whose work focused on fruit flies and established the **chromosome theory of inheritance** and concepts like linkage and crossing over. - While significant to genetics, his work does not describe the constancy of allele frequencies in a population. *Mendel's Law* - **Mendel's Laws of Inheritance** (segregation and independent assortment) describe how traits are passed from parents to offspring through the inheritance of discrete units (genes). - While fundamental to explaining inheritance, they do not directly state that allele frequencies remain constant in a population across generations under specific conditions, as the Hardy-Weinberg law does.

Question 5: 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 ?

A. Both 1 and 2 (Correct Answer)
B. 1 only
C. 2 only
D. Neither 1 nor 2

Explanation: ***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.

Question 6: Which of the following fats has the highest concentration of saturated fatty acids ?

A. Butter
B. Margarine
C. Coconut oil (Correct Answer)
D. Palm oil

Explanation: ***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**.