5.2.3 The Mammalian Liver: Function

Question 1

Hepatocyte functions :

Answer 1

• Storage of glycogen (for glycogenolysis)
• Formation of urea
• Detoxification

Question 2

How is urea formed in the liver? (from proteins being digested)

Answer 2

• Protein digested to amino acids
• Absorbed and transported to liver
• Excess amino acids are a good source of energy, so aren’t excreted
• They are deaminated (-NH2 group and H removed)
• Form ammonia (NH3)
• Forming Ammonium ions in cytoplasm (NH4+)
• Keto acid remaining enters kreb’s cycle for respiration, or is converted to glucose (gluconeogenesis)

Ammonia is very soluble and highly toxic, produced in deamination. Ammonia is combined with CO2 to form urea which is less toxic. Urea transported to kidneys.

Question 3

What is detoxification in liver? 4 examples

Answer 3

The breakdown of substances that are not needed or toxic

• Lactate (product of anaerobic respiration, energy rich for respiration, absorbed by hepatocyte converted to pyruvate to be respired, or converted to glucose)
• Alcohol (alcohol dehydrogenase converts ethanol to ethanal, which enters kreb’s cycle)
• Hormones (protein hormones hydrolysed to amino acids which are converted to urea)
• Medicinal drugs

Question 4

What is fatty liver?

Answer 4

• Ethanol metabolism generates lots of ATP
• Hepatocytes then metabolise less fats and so store fats
• Causing buildup of fat making hepatocytes less functional, can cause fibrosis