liver metabolism Flashcards
what circulation drains the gut?
portal circulation
what is a hepatic lobule?
structural unit of the liver
how does blood enter a hepatic lobule?
enters via portal venule and the hepatic arteriole
how does all dietary carbohydrate reach the liver?
as glucose
what is sucrose broken down into?
fructose and glucose
what is lactose broken down into?
galactose and glucose
what is starch broken down into?
maltose and glucose
what is glycogenesis?
glucose –> glycogen
what is glycogenolysis?
breaking down of glycogen
in the presence of oxygen, what process does glucose feed into?
Krebs cycle
how can hepatocytes generate glucose?
gluconeogenesis from materials such as lactate, pyruvate, amino acids and glycerol
what are the functions of insulin?
Counteracted by glucagon.
Promotes glycogen synthesis
Suppresses gluconeogenesis
Accelerates glycolysis
what are essential amino acids?
need to be taken up through diet
what is transamination?
transfer of amino group to keto-acid catalysed by transaminase
what are alanine and aspirate aminotransferases indicators of?
hepatic injury
when hepatocytes die they release this enzyme
what is deamination?
removing an amino group
what does deamination form?
often forms a keto acid and an ammonium ion
why is excess ammonia dangerous?
depletes ketoglutarate which is used in Krebs cycle increases level of glutamate increases osmotic pressure astrocytes swell increases cranial pressure
how is ammonia produced?
deamination and gut bacteria
how is ammonia removed from the body?
NH3 reduced to NH4
NH4 –> urea through urea cycle
what is raised serum urea an indicator of?
renal failure bc urea is secreted into the kidneys
also could show there’s too much ammonia
what is plasma?
liquid component of blood- cell free
what does plasma contain?
albumin, globulins, clotting factors, water, glucose and electrolytes
where are most plasma proteins made?
in the liver
what is blood serum?
blood without the clotting factors
how are lipids transported?
lipoproteins
what are lipoproteins?
arrangement of phospholipid layer with non-soluble material on the inside
what can triglycerides be broken down into?
fatty acids and glycerol
how can fatty acids be used?
to make acetyl coA –> respiration, cholesterol synthesis
how can glycerol be used?
can be converted to glucose in gluconeogenesis
what does the liver do with excess glucose?
excess glucose to fatty acids, synthesizes phospholipids and ketone bodies
when does ketogenesis occur?
in the absence of glucose - switched off by insulin
what does ketogenesis do?
breaks down lipids and proteins
fatty acids can then be converted to acetyl coA to produce ketone bodies
what is bile?
emulsifier that dissolves fat
what organ makes bile?
the liver
where is bile stored?
the gall bladder
which cells secrete bile?
hepatocytes in canaliculi
what is bile made of?
water (>90%), bile salts, bilirubin, cholesterol, fatty acids, lecithin, Na+/K+/Ca2+/Cl-
what are cholangiocytes and what are their function?
epithelial cells of the bile ducts, can modify bile (production) by the addition of HCO3-
what does CCK stimulate?
gall bladder contraction and sphincter of Oddi relaxation
what stimulates the secretion of CCK?
in response to fatty acids being in the lumen of the duodenum
what stimulates the secretion of secretin?
presence of acidic chime in duodenum
what is formed when cholesterol is oxidised?
cholic acid and chenodeoxylic acid
where are bile salts absorbed?
in the ileum
if bile salts are not reabsorbed, where do they move?
to the colon
what can bile salts in the colon cause?
diarrhea due to the increased oncotic pressure of bile salts in the lumen
what is exogenous cholesterol?
cholesterol from the diet
what is endogenous cholesterol?
cholesterol synthesised in the liver
what effect do statins have on the endogenous products of cholesterol?
inhibit
where are red blood cells broken down?
in the spleen
what is haemoglobin broken down into?
heme and globin
what does the non-heme part of haemoglobin turn into?
bilirubin
what protein does bilirubin bind to?
albumin
what is the cause of jaundice?
build up of bilirubin
