UPSC-CMS 2010 — Biochemistry

Q: Which one of the following biochemical abnormalities can be produced by repeated vomiting?

Metabolic alkalosis. ***Metabolic alkalosis*** - Repeated vomiting leads to the loss of **hydrochloric acid (HCl)** from the stomach, causing **hypochloremic metabolic alkalosis** with an increase in serum **bicarbonate (HCO3-)** and a rise in blood pH. - The loss of H+ and Cl- ions results in **compensatory hypokalemia** as the kidneys exchange K+ for H+ to maintain electroneutrality. - **Volume depletion** from vomiting triggers aldosterone secretion, which further promotes K+ loss and H+ excretion, perpetuating the alkalosis (contraction alkalosis). - This is one of the most common causes of metabolic alkalosis in clinical practice. *Metabolic acidosis* - This condition is characterized by a decrease in **serum pH** and **bicarbonate levels**, typically due to excess acid production or bicarbonate loss from diarrhea or renal tubular acidosis. - Vomiting does not directly cause metabolic acidosis; rather, it leads to the opposite effect by removing acidic gastric contents. *Ketosis* - **Ketosis** occurs when the body metabolizes fat for energy, producing **ketone bodies**, common in conditions like uncontrolled diabetes or prolonged starvation. - While severe, prolonged vomiting with reduced oral intake can indirectly lead to starvation ketosis, the primary and most characteristic biochemical abnormality of repeated vomiting is metabolic alkalosis, not ketosis. *Uraemia* - **Uraemia** is a syndrome caused by the accumulation of **nitrogenous waste products** (urea, creatinine) in the blood, primarily due to kidney failure. - Vomiting may be a *symptom* of uraemia, but it does not *cause* uraemia. Kidney function is the primary determinant of urea levels. [Practice more Biochemistry PYQs on OnCourse]

Q: Biochemical screening of newborn infants by heel-prick blood samples is performed by using the

Guthrie Card. ***Guthrie Card*** - The **Guthrie card**, also known as a **newborn screening card** or **filter paper card**, is specifically designed for collecting **heel-prick blood samples** from newborn infants for biochemical screening. - It allows for the detection of various **inborn errors of metabolism** and other genetic conditions, such as **phenylketonuria (PKU)** and **congenital hypothyroidism**. *Duchenne Card* - There is no specialized "Duchenne Card" used for **newborn biochemical screening**. - **Duchenne muscular dystrophy** is a genetic disorder diagnosed through **genetic testing** or **muscle biopsy**, not typically a specific screening card at birth. *Tay-Sachs Card* - There is no specific "Tay-Sachs Card" used for routine **newborn biochemical screening**. - **Tay-Sachs disease** is a **lysosomal storage disorder** diagnosed through enzyme activity tests or **genetic analysis**, often in populations at higher risk or with clinical suspicion. *Maple Card* - There is no recognized "Maple Card" for **newborn biochemical screening**. - "Maple" could potentially refer to **Maple Syrup Urine Disease (MSUD)**, which is one of the conditions screened for using the **Guthrie card**, but there is no dedicated "Maple Card." [Practice more Biochemistry PYQs on OnCourse]

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Which one of the following biochemical abnormalities can be produced by repeated vomiting?

Biochemical screening of newborn infants by heel-prick blood samples is performed by using the