The mammalian liver: function 5.2.3 Flashcards
What are three functions of the liver?
- Storage of glycogen
- Formation of urea
- Detoxification
What is glycogenesis?
The conversion of glucose into glycogen
Where is the glycogen produced during glycogenesis stored?
Inside hepatocytes
Where and how are amino acids transported following digestion?
They’re absorbed into the blood and transported to the liver via the hepatic portal vein
How are excess amino acids processed inside hepatocytes?
- deamination
- the ornithine cycle
Describe deamination
During deamination:
- The amino group (NH2) is removed from each amino acid, along with an extra hydrogen atom
- NH2 and H combine to form ammonia (NH3)
What is the part of the amino acid that remain after deamination, and where does it go?
A keto acid, which is issued for:
- entering the Krebs cycle for respiration
- be converted to glucose
- be converted to glycogen or fat for storage
Briefly describe the ornithine cycle
Ammonia is converted into urea, as it is less toxic than ammonia.
Ammonia is combined with carbon dioxide to form urea
Urea then diffuses through the phospholipid bilayer of the hepatocytes and is transported to the kidneys dissolved in the blood plasma
What is detoxification?
The breakdown of substances that are not needed, or are toxic
What are the substances that undergo detoxification?
- alcohol
- lactate
- medicinal drugs
Describe the detoxification of alcohol
- Once consumed, ethanol is absorbed in the stomach and is transported in the blood until it reaches hepatocytes
- Inside hepatocytes, alcohol dehydrogenase converts ethanol into ethanal, which is then converted into other molecules that enter respiration
Why can continuous alcohol detoxification cause liver problems?
- The metabolism of alcohol generates ATP, so hepatocytes do not metabolise as much fat as usual and instead store the fat, leading to fatty liver
- Stored fat reduces the ability of hepatocytes to carry out other functions and can eventually lead to severe problems such as cirrhosis, which is scarring of the liver caused by excessive alcohol consumption