Metabolism of the Liver Flashcards
why is poo brown
it’s full of bilirubin
What colour is stool in end stage liver disease
White
liver isn’t breaking down things into bilirubin
Principle roles of the liver
First destination of most neutrinos and xenobiotics absorbed from GI tract Bile production Elimination of unwanted molecules secretion of plasma proteins secretion of important molecules Regulation of metabolism -carb and lipid metabolism (fuel) -amino acid metabolism (urea cycle)
what plasma proteins are metabolised in the liver
Albumin alpha globulin beta globulin gamma globulin immunoglobumins
What are the main functions of plasma proteins
maintenance of oncotic or colloid osmotic pressure -dont exit into interstitial fluid -prevents loss of plasma proteins Transport of hydrophobic substances pH buffering Enzymatic (blood clotting) Immunity
What is the role of alpha globulins
transport lipoproteins, lipids, hormones and bilirubin
retinol binding protein
transports vitamin A
What is the role of beta globulins
Transferrin -transports iron -levels an indicator of iron deficiency Fibrinogen -inactive form of fibrin -clotting of blood
What is the role of albumin
Main determinant of plasma oncotic pressure
Transporter functions
Which plasma protein is the most abundant
albumin - 50% of all plasma proteins
Where is albumin synthesised
the liver
what stimulates albumin synthesis
Insulin
When are albumin levels low
In liver disease
What decreases levels of albumin
starvation/ low protein diet decreases levels of albumin
What are the transport functions of albumin
Multiple binding sites for hydrophobic molecules
transports endogenous lipophilic substances
-fatty acids, bilirubin, thyroid hormones
transports exogenous substances
-drugs like aspirin
How is iron transported
as ferric ion Fe3+ bound to transferrin (beta globulin)
What is iron bound to when it is stored in cells
Ferritin
An example of copper deficiency
Wilson’s disease
What is copper bound to when transported in blood
ceruloplasmin
What controls the transport and stability of steroid hormones in the blood
specific transport molecules eg.
thyroid-binding globulin
cortisol binding globulin
What are lipoproteins
hydrophobic proteins allowing the transport and solubilisation of lipids as low density lipoprotein protein particles
What is the shell surrounding lipoproteins made of
polar lipids (phospholipids) apoproteins
Role of lipoproteins in the rest system
Production and secretion of surfactant
What are chylomicron lipoproteins
found in intestine
transport exogenous fat to liver
VLDL origin and function
Liver
transport of exogenous fat to peripheral cells
IDL origin and function
VLDL
LDL precursor
LDL function and origin
VLDL, ILDL, Liver
transport cholesterol to peripheral tissues
HDL origin and function
Intestine and liver
Transport of cholesterol from peripheral tissues to liver
What vitamins are stored in the liver
Vitamin A
Vitamin D
Vitamin B12
Also iron (from breakdown of Hb)
What is cholesterol
component of cell membranes which increase rigidity
What is cholesterol a precursor for
- bile acids
- steroid hormones
- vitamin D
How much circulating cholesterol is in free form
30%
How is most cholesterol circulated
As esterified to a variety of long-chain fatty acids
What causes cholesterol to be solubilised
incorporation into lipoproteins
How is cholesterol stored
As lipid droplets
Where does cholesterol synthesis start (step 1)
Acetyl-CoA
NADPH -reducing power
ATP -energy
Where is cholesterol synthesised
cytoplasm of virtually all human cells
Mainly liver
What is HMG-CoA reductase
Rate limiting enzyme in the synthesis of cholesterol
can be a target for statins
What is the role of vitamin D
made from cholesterol
regulation of calcium and phosphorus metabolism
What vitamin D is most abundant
Vitamin D3
What steroid hormones are synthesised from cholesterol
Corticosteriods
Androgens
Estrogens
What is the precursor for bile salts
Cholesterol
