UPSC-CMS 2019 — Biochemistry

Q: Which one of the following trace elements if deficient in the diet can lead to low birth weight, preterm delivery, spontaneous abortion or even congenital malformation like anencephaly?

Zinc. ***Zinc*** - **Zinc deficiency** during pregnancy is associated with low birth weight, preterm delivery, spontaneous abortion, and congenital malformations like **anencephaly** due to its crucial role in cell growth, differentiation, and DNA synthesis. - Adequate zinc levels are essential for proper fetal development and maternal immune function. *Copper* - **Copper deficiency** can lead to issues such as anemia, neurological problems, and impaired bone development, but it is not primarily linked to the specific spectrum of adverse pregnancy outcomes described in the question, such as anencephaly. - While important, copper's role in fetal development differs from zinc's broad impact on cellular processes. *Selenium* - **Selenium deficiency** can be associated with increased risk of preeclampsia, miscarriage, and impaired fetal growth, but it is not as strongly linked to **neural tube defects** like anencephaly as zinc. - Primarily functions as an antioxidant and in thyroid hormone metabolism. *Cobalt* - **Cobalt** is a component of vitamin B12, and its deficiency is usually observed as a deficiency in vitamin B12, leading to **megaloblastic anemia** and neurological issues. - Direct independent cobalt deficiency is rare and not directly associated with the described pregnancy complications or **congenital malformations** in humans. [Practice more Biochemistry PYQs on OnCourse]

Q: Which one of the following conditions is NOT inborn error of metabolism?

Neural tube defects. ***Neural tube defects*** - Neural tube defects are **birth defects** that occur when the **neural tube** fails to close completely during early fetal development, typically affecting the brain, spinal cord, or both. - While they are congenital, they are not classified as **inborn errors of metabolism** because they primarily result from structural developmental anomalies rather than enzymatic pathway dysfunctions. *Phenylketonuria (PKU)* - PKU is an **autosomal recessive** inborn error of metabolism caused by a deficiency of the enzyme **phenylalanine hydroxylase**, leading to a buildup of phenylalanine. - This enzymatic defect impairs the body's ability to metabolize **phenylalanine**, making it a classic example of an inborn error of metabolism. *Maple syrup urine disease* - This is an **autosomal recessive** inborn error of metabolism characterized by a defect in the metabolism of **branched-chain amino acids** (leucine, isoleucine, and valine) due to a deficiency in the enzyme branched-chain alpha-keto acid dehydrogenase. - The accumulation of these amino acids and their keto-acids gives the urine a characteristic **maple syrup odor**. *Tay-Sachs disease* - Tay-Sachs disease is a fatal, **autosomal recessive** inborn error of metabolism caused by a deficiency of the enzyme **hexosaminidase A**. - This enzyme deficiency leads to the harmful accumulation of fatty acid derivatives called **gangliosides** in nerve cells in the brain, resulting in progressive neurological degeneration. [Practice more Biochemistry PYQs on OnCourse]

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Which one of the following trace elements if deficient in the diet can lead to low birth weight, preterm delivery, spontaneous abortion or even congenital malformation like anencephaly?

Which one of the following conditions is NOT inborn error of metabolism?