5.1.2 Excretion, Homeostasis And Liver Flashcards
What is excretion
The removal of the waste products of metabolism
What are the main metabolic waste products
Carbon dioxide - a waste product of cellular respiration. Removed by excretion from lungs
Bile pigments - formed from the breakdown of haemoglobin from old red blood cells in the liver. They are extracted in the bile from the liver into the small intestine via the gall bladder and bile duct. These are what colour you’re faeces
Nitrogenous waste compounds - formed from the breakdown of excess amino acids by the liver. All mammals produce urea as their nitrogenous waste. Fish produce ammonia and uric acid is secreted by insects
What major role does the liver play and where is it?
It is a major organ that plays a big role in homeostasis. It is reddish brown that makes up 5% of our total body mass. It is the largest internal organ. It lies below the diaphragm and is made up of several lobes. It is very fast growing and damaged areas regen hella quick
How much blood flows through the liver per minute and how does blood reach liver?
1dm3 flows through liver every minute. Oxygenated bloods gets supplied to liver by hepatic artery and removed from liver to the heart by hepatic vein. Blood is also supplied to liver via a second vessel called the hepatic portal vein. This however carries blood loaded with products of digestion straight from the intestines to the liver and this is the starting point for many metabolic activities of the liver. Around 75% of blood to liver comes from hepatic portal bein
Structure of liver cells?
Also known as hepatocytes have large nuclei, prominent Golgi apparatus and lots of mitochondria, indicating that they are very metabolically active. They divide and replicate hella.
Where does blood from Hepatic artery and hepatic portal vein go to
They are mixed in spaces called sinusoids which are surrounded by hepatocytes. This increases oxygen content of blood from hepatic portal vein, supplying hepatocytes with enough oxygen for their needs. The sinusoids contain kupffer cells which act as the resident macrophages of the liver, ingesting foreign particles and helping protect from disease.
What do hepatocytes secrete?
They secrete bile from the breakdown of the blood into spaces called canaliculi, and from these, the bile drains into bile ductules which take it to the gall bladder.
How does the liver help carbohydrate metabolism
Hepatocytes are closely involved in the homeostatic control of glucose levels in the blood by their interaction with insulin and glucagon. When blood glucose rises, insulin levels also rise and stimulates hepatocytes to to convert glucose into glycogen store.and when blood glucose starts to fall, hepatocytes convert glycogen back into glucose under the influence of the hormone glucagon
What is transamination
The conversion of one amino acid into another. This is required as the diet may not have the correct balance of amino acids. But transamination can overcome this.
What is deamination in protein metabolism
The removal of an amine group of a molecule. The body cant Store proteins or amino acids and any excess would be excreted and therefore wasted if it were not for the action of hepatocytes in the liver. They deaminate amino acids, removing the amino group and converting it into ammonia and then to urea. This is very toxic in high concs, but chilling normally. Urea then excreted by kidney. Remainder of amino acids are then fed into cellular respiration or converted into cellular respiration or lipids.
How is ammonia converted into urea
Through a set of enzyme controlled reactions known as the ornithine cycle.
What is detoxification
Where liver detoxifies a wide varieties of toxins that we take in and makes them harmless. One example is the break down of hydrogen peroxide, a by product of metabolism. Hepatocytes have enzyme catalase which helps split hydrogen peroxide into oxygen and water.
Another example is the detoxification of ethanol. Hepatocytes have the enzyme alcohol dehydrogenase that breaks down ethanol into ethanal. Ethanal is then converted into ethanoate which is used to build up fatty acids or used in cellular respiration
