15.4 Excretion, homeostasis and the liver Flashcards
What occurs in detoxification
The liver is where detoxification of toxic substances from metabolic waste occurs.
E.g. the breakdown of hydrogen peroxide. Hepatocytes contain the catalase enzyme.
Hepatocytes contain alcohol dehydrogenase which detoxifies ethanol to ethanal.
Ethanal is converted to ethanoate which is used to build up fatty acids to be used in cellular respiration.
Define excretion
the process by which toxic waste products of metabolism are removed from the body
What’s egestion
The removal of undigested food from the body
3 examples of metabolic waste products that are excreted
CO2 – cellular respiration waste product – excreted from lungs
Bile pigments – formed from breakdown of Hb in old red blood cells in the liver. Excreted in bile from the liver > small intestine via the gall bladder and bile duct
Nitrogenous waste products (urea) – formed from breakdown of excess aas in the liver. All mammals produce urea as nitrogenous waste
3 features of the liver
Grows quickly, when damages it regenerates very fast
Liver has a rich blood supply
Blood returns to the heart via the hepatic vein
Where does the liver gets its blood supply from
Supplied by the hepatic artery (oxygenated; supplies hepatocytes with oxygen) and the hepatic portal vein – partially deoxygenated - (which carries blood with digested food products from the intestines to the liver; 75% of the blood comes from the HPVein)
What are hepatocytes and what’s their structure like
They are liver cells: Large nuclei; Prominent Golgi Apparatus; Many mitochondria which produce ATP for metabolic activity
What are sinusoids
Spaces where blood from the hepatic artery and hepatic portal vein is mixed. It is surrounded by hepatocytes
What are kupffer cells
Resident macrophage – they ingest foreign particles and help protect against diseases
What is deamination and what occurs during it
the removal of an amine (-NH2) from a molecule
The body is unable to store proteins or amino acids.
The liver initially deaminates amino acids, converts to ammonia first (very toxic), then urea.
Urea is toxic in high conc. Urea is excreted to the kidney for excretion.
Remainder of the aas is fed into cellular resp of converted to lipids for storage.
What is transamination
conversion of one aas to another, the diet does not contain all the essential amino acids, transamination solves this
What occurs during the orthine cycle
Where ammonia becomes urea during a set of enzyme controlled reactions
What are bilecanaliculus
The hepatocytes secrete bile into these and it drains I to the gall bladder to be stored
What are the functions of the liver
Carbohydrate metabolism
Deamination of excess amino acids
Detoxification
What is the process of carbohydrate metabolism
Hepatocytes are involved in homeostatic control of glucose. When blood glucose levels rise, hepatocytes are stimulated to convert glucose to glycogen. When blood sugar levels fall, the opposite happens using glucagon hormone
After deamination what happens to the remained of the amino acid
It’s fed into cellular respiration or converted into lipids for storage
