Biochemistry Topics

Question 1

Explain the Urea cycle

Answer 1

The breakdown of amino acids for energy produces NH3 (ammonia) that is toxic to the body. To deal with this, NH3 is combined with CO2 in the mitochondrial matrix to form Carbamoyl Phosphate that is converted to Urea in the liver cytoplasm by the Urea Cycle. The Urea is then easily excreted by the kidneys.

Question 2

Explain the metabolism of bilirubin

Answer 2

Bilirubin is produced by the breakdown of RBC’s producing free heme

Free heme is processed by macrophages to produce biliverdin

Biliverdin becomes unconjugated bilirubin that then binds to albumin and is transported to the liver

In the liver, bilirubin is conjugated ot glucuronic acid and is excreted in bile to the intestines

In the intestines, conjugated bilirubin is converted to urobiliogen and urobilin and 90% is excreted in feces sometimes as stercobilin

The remaining 10% is reabsorbed and transported back to the liver where it can re-enter the blood to be excreted by the kidneys or be re-excreted in the bile

Question 3

Explain the purpose of 5alpha-reductase

Answer 3

It is an enzyme used to convert testosterone into DHT, the most potent form of the hormone