BI5.1-9 | Chemistry & Metabolism of Proteins and Immunology — Practice Quiz

An amino acid that the human body cannot synthesise and must be obtained from the diet is classified as 'essential'. Which of the following is an essential amino acid?

A protein with quaternary structure consists of multiple polypeptide subunits assembled into a functional complex. Which of the following proteins has quaternary structure?

In protein digestion, trypsinogen is an inactive zymogen secreted by the pancreas. Which enzyme activates trypsinogen to trypsin, and where does this activation occur?

Serum protein electrophoresis of a 65-year-old man with bone pain and recurrent infections shows a tall, narrow spike in the gamma-globulin region (M-spike). This pattern is most consistent with:

Which class of immunoglobulin is the ONLY one that crosses the placenta, providing passive immunity to the newborn?

The urea cycle detoxifies ammonia in the liver. Which enzyme catalyses the rate-limiting step of the urea cycle, and where in the cell does it function?

A patient with advanced liver cirrhosis develops confusion, asterixis (flapping tremor), and elevated blood ammonia. Which mechanism BEST explains the brain toxicity caused by hyperammonaemia?

A newborn screening test (heel-prick at 48 hours) reveals elevated phenylalanine levels. The baby is diagnosed with classical phenylketonuria (PKU). Which enzyme is deficient, and what is the mainstay of treatment?

A 4-day-old neonate develops jaundice with elevated unconjugated (indirect) bilirubin. The jaundice is physiological. Which of the following BEST explains physiological jaundice of the newborn?

A patient is brought to the emergency department after exposure to a house fire. They are drowsy but have cherry-red skin colour. Pulse oximetry reads 98%. Which haemoglobin derivative is most likely responsible for this presentation, and why is pulse oximetry misleading?