Physiology of liver, pancreas and gallbladder Flashcards
What is Fe2+ stored in the liver as?
ferritin
Iron is transported bound to which protein?
transferrin
How much glycogen is stored in the liver?
100g
What are the fat soluble vitamins?
ADEK
How long can the liver’s glycogen stored last for?
12 hours
How long can the liver’s fat stores last for?
3 months
What is the aim of liver detoxification?
Aims to either make the substance less toxic or increase solubility to allow the substance to be excreted
Describe phase 1 reactions
oxidation or hydrolysis reactions
Describe phase 2 reactions
Glucoronidation
Conjugation
Excretion
What is glucaronidation?
addition of glucaronic acid to a substance
What is conjugation?
addition of a chemical group to a substance
What does Gilbert’s syndrome cause?
Mild jaundice as a result of inefficiant UDPGT
What can colloid osmotic pressure also be referred to as?
oncotic pressure
What is oncotic pressure?
form of osmotic pressure induced by proteins in the vessel
What are the main functions of albumin?
maintaining oncotic pressure
binding and transporting large/hydrophobic molecules
All but which clotting factors are produced in the liver?
All but 4 and 7
What are the vitamin K dependent clotting factors?
10, 9, 7, 2
What is produced by the liver that is important for the absorption of vitamin K and other fat soluble vitamins?
bile salts
What three types of protein are produced by the liver?
Plasma protein e.g albumin
Clotting proteins
Complement proteins (part of immune response)
What is the purpose of the glucose-alanine cycle?
to move proteins from the muscle to the liver when glycogen stores are low
What is an important enzyme involved in the glucose-alanine cycle? Its concentration in serum is used to measure liver health.
Alanine aminotransferase (ALT)
In the glucose-alanine cycle, what does is glucose converted into in the muscle?
pyruvate
In the glucose-alanine cycle, what is pyruvate converted into in the muscle. What enzyme is required for this step?
pyruvate is converted into alanine
alanine aminotransferase is required for this step
Apart from pyruvate and alanine aminotransferase, what other substance is required to produce alanine at the muscle?
glutamate
What is glutamate converted into at the muscle in the glucose-alanine cycle?
alpha-ketoglutarate
What is the next step of the glucose-alanine cycle after alanine has been produced in the muscle?
alanine travles in the blood to the liver
What is alanine converted to in the liver?
pyruvate
In the glucose-alanine cycle, what is pyruvate converted into at the liver?
glucose
Where does glutamate come from initially in the glucose-alanine cycle?
muscle proteins
Which cycle is similar in function to the glucose-alanine cycle except more productive?
the Cori cycle
Describe what happens to glucose in the muscle in the Cori cycle
Glucose is converted to 2 pyruvate
2 pyruvate is converted to 2 lactate
In the Cori cycle, what is used to produce glucose from in the liver
2 lactate
In the Cori cycle, what is 2 lactate converted to in the liver?
2 lactate is converted to 2 pyruvate
2 pyruvate is converted to glucose
What is NH3?
ammonia
What neurotoxic substance does the urea cycle remove?
ammonia
In the urea cycle, what is added to ornithine to form citrulline?
ammonia and CO2
In the urea cycle, what is added to citrulline to form arginine?
ammonia
What does arginine release to regenergate ornithine?
Urea
In the urea cycle, the release of urea from arginine forms what substance?
ornithine
what does LDL stand for?
low density lipoproteins
what does HDL stand for?
high density lipoproteins
What does VLDL stand for?
very low density lipoproteins
What type of lipoprotein is used to transport lipids from the liver to adipose tissue?
VLDL
What cell is the main store of lipids?
adipocytes
When VLDLs reach adipocytes, how does the fat enter the adipocyte?
VLDLs release their triglycerides
triglycerides diffuse into adipocytes
Emulsification of fatty acids by bile forms what ?
micelles
Where in the GI tract does lipid digestion primarily occur?
the small intestine (but some occurs in the mouth and stomach)
Lipase converts triglycerides into?
monoglyercide +2 fatty acids
Describe the solubility of pancreatic lipase?
water soluble
Why can pancreatic lipase only act on the surface of fat droplets?
It is water soluble
Which enzyme holds lipase to the surface of the lipid droplet?
colipase
How do the fatty acids + monoglycerides get into the epithelial cells?
via diffusion
Where in the intestinal epithelial cells are monoglycerides and fatty acids resynthesised into triglycerides?
smooth endoplasmic reticulum
What are triglycerides packaged into after their resynthesis in the intestinal epithelial cells?
chylomicrons
What type of vessel do chylomicrons pass into from the intestinal epithelial cells?
lacteals
Where are LDLs formed and what is their function?
formed in plasma
deliver cholesterol to cells
Where are high density lipoproteins formed and what do they do?
formed in the liver
remove excess cholesterol from blood and tissues via excretion in bile
Where are VLDLs formed and what do they do?
formed in liver (hepatocytes)
deliver triglycerides from liver to adipocytes
Which type of lipoprotein delivers cholesterol to cells?
low density lipoproteins
Which type of lipoprotein removes excess cholesterol from the blood and tissues via excretion in bile?
High density lipoproteins
What essentially is fatty acid beta oxidation?
breaking down lipids to release energy
Each cycle shortens the fatty acid chains by 2 carbons until the fatty acid is only 2 carbons long
Where does fatty acid beta oxidation occur?
the mitochondria of hepatocytes
What type of cell continuously secretes bile?
hepatocytes
What components are in bile?
bile salts lecithin (a phospholipid) HCO3- Cholesterol Bile pigments e.g bilirubin
What is lecithin?
a phospholipid
Bile is released from the gallbaldder in response to which hormone?
CCK
Which type of bilirubin is toxic and lipid soluble?
unconjugated bilirubin
Which type of bilirubin is water soluble?
conjugated bilirubin
Which cells phagocytose red blood cells? what is hemoglobin broken down into?
macrophages
hemoglobin is broken down into heme and globin
What happens to the globin from the breakdown of hemoglobin?
globin is hydrolysed to from amino acids and these are used to make new proteins
Which enzyme breaks down heme into biliverdin and Fe2+?
heme oxygenase
What are the products of the breakdown of heme by heme oxygenase?
biliverdin and Fe2+
Biliverdin results from the breakdown of what substance?
heme
What colour is biliverdin?
green
What is biliverdin converted into by the enzyme biliverdin reductase?
unconjugated bilirubin
Which enzyme converts biliverdin into unconjugated bilirubin?
biliverdin reductase
What colour is unconjugated bilirubin?
yellow
Where is unconjugated bilirubin converted into conjugated bilirubin + glucaronic acid ?
the liver
What does the liver convert unconjugated bilirubin into?
conjugated bilirubin and glucaronic acid
How is conjugated bilirubin excreted from the liver?
In bile
What is conjugated bilirubin converted into in the ileum and the beginning of the large intestine?
urobilinogen
What converts conjugated bilirubin into urobilinogen?
bacteria
How do bacteria convert unconjugated bilirubin into urobilinogen ?
remove glucaronic acid
Describe the solubility of urobilinogen?
lipid soluble
What is the majority of urobilinogen oxidised to form?
stercobilin
What colour is stercobilin?
brown
What chemical is responsible for the brown colour of feces?
stercobilin
What percentage of urobilinogen is reabsorbed and bound to albumin in the blood?
10-15%
What is urobilinogen converted into at the kidneys?
urobilin
Which chemical is primarily responsible for the yellow colour of urine?
urobilin
What happens to the reabsorbed urobilinogen that does not go to the kidneys ?
enters the enterohepatic urobilinogen cycle and is resecreted into the bile
What is the cause of jaundice?
increased bilirubin in the blood
What are the different types of jaundice?
pre hepatic
hepatic
post hepatic
Describe post hepatic jaundice
impaired excretion due to mechanical obstruction to bile flow
elevated conjugated bilirubin in serum
Describe pre hepatic jaundice
excessive hemolysis
elevated unconjugated bilirubin in serum
How is unconjugated bilirubin transported to the liver?
via albumin
What enzyme is involved in the conversion of unconjugated bilirubin into conjugated bilirubin?
UDPGT
What colour is bilirubin in bile?
yellow/green
What are the exocrine secretions of the pancreas?
HCO3-
Zymogens
Digestive enzymes
What does the pancreas secrete that neutralises chyme in the duodenum?
HCO3-
Where are the zymogens secreted by the pancreas activated?
the duodenum
What part of small intestine releases secretin?
the duodenum
What hormone stimulates HCO3- secretion from the pancreas?
secretin
How is HCO3- secreted by pancreatic duct cells?
a Cl-/HCO3- exchanger
What is HCO3- exchanged for when it is secreted by the duct cells of the pancreas?
Cl-
Cl- brought into pancreatic duct cells are recycled back into the lumen by what channel?
CFTR channels
What is the function of CFTR channels?
movement of Cl- from inside the pancreatic duct cell into the lumen
Which channel is non-functional in cystic fibrosis?
CFTR
Give two examples of zymogens
trypsinogen
chymotrypsinogen
Which enzyme is key for activating zymogens?
enterokinase
trypsin also plays an important role in the activation of zymogens
What is the function of trypsin?
digests proteins
activates zymogens
What is the function of alpha-amylase?
digests starch into maltose
What hormone inhibits the release of digestive enzymes?
somatostatin
What cell type produces pancreatic lipase, trypsin and alpha-amylase?
pancreatic acinar cells
What hormone stimulates the release of pancreatic digestive enzymes?
CCK
What do alpha cells in the pancreas secrete?
glucagon
What do beta cells in the pancreas secrete?
insulin
What do delta cells in the pancreas secrete?
somatostatin
What hormone inhibits pancreatic exocrine secretion as well as glucagon and insulin secretion ?
somatostain
What is CCK released by?
the duodenum
