Biochemical aspects of liver metabolism Flashcards
Where is bile produced?
Liver
Name a plasma protein which is secreted in the liver
Albumin
What important molecules are stored in the liver?
Fuels, Iron, Vitamins
By what 2 processes are unwanted molecules eliminated?
Metabolism
Excretion into the biliary tree and faecal excretion
What is the importance of carbohydrate and lipid metabolism
Fuel storage
What is the importance of the amino acid metabolism
Urea cycle
What is electrophoresis
It allows the separation of proteins by size
Name 5 functions of plasma proteins
Maintenance of oncotic or colloid osmotic pressure Transport of hydrophobic substancces pH bufferring Enzymatic Immunity
What is the purpose of maintaining osmotic pressure
Prevents the loss of plasma proteins
Name some hydrophobic substances transported by plasma proteins
Steroid hormones
Free fatty acids
bilirubin
cholesterol
Name an ezymatic function of plasma proteins
Blood clotting
What are the 2 main substances secreted through plasma protein secretion
Albumin and alpha globulins
What do alpha globulins do?
Transport lipoproteins, lipids, hormones and bilirubin
What does retinol binding protein do?
Transports vitamin A
Name the main two beta globulins
Transferrin and fibrinogen
What is the function of Transferrin
Transports Fe3+
Indicator or iron deficiency
What is the function of fibrinogen
Inactive for of fibrin
Involved in the clotting of blood
What is Albumin and what is its main roll
Most abundant plasma protein
Small, negatively charge, water soluble protein
It is the main determinant of plasma oncotic pressure
How much albumin does the liver synthesise per day
14g
What stimulates the synthesis of albumin
Insulin
What causes low levels of albumin
Liver disease
Starvation / low protein diet
What is iron? How is it transported? and how is it stored?
It is a component of haemoglobin, myoglobin and cytochromes
Transported as ferric ion Fe3+ bound to transferrin
Stored in cells bound to ferritin
How is copper transported in the blood
Bound to ceruloplasmin
What is the roll of copper
Essential for regulation of redox reactions, transport and use of iron
What is the disease called where there is a copper deficiency
Wilson’s disease
What 2 groups of hormones are hydrophobic
Steroid hormones
T3/T4 thyroid hormones
How are hormones transported
In the circulation bound to specific transport molecules
What is thyroxine bound to?
Thyroid-binding globulin
What is cortisol bound to
What is cortisol bound to
Cortisol binding globulin
What is the purpose of hormone transport
They extend biological half life and increase plasma concentration
Describe a lipoprotein
Hydrophobic
surrounded by a shell
Free cholesterol dispersed throughout
What is the roll of a lipoprotein
To transport fat between organs and tissues
What is the function of cholesterol transport
It removes excess cholesterol from cells
Where is cholesterol metabolised and excreted
Liver
How is cholesterol degraded
Esterified with fatty acids
Transported back to the liver
Excreted as bile salts via biliary system or faceces
What 3 vitamins are stored in the liver ?
Vitamin A,D and B12
What does cholesterol do in terms of mammalian cell membranes
Increases the rigidity of them
What 3 classes of compounds is cholesterol a precursor for
Bile acids
Steroid hormone
Vitamin D
Why is the metabolism of cholesterol important?
Etiology of cardiovascular disease
Major component of gall stones
How is the majority of cholesterol transported
Esterified to a wide range of long-chain fatty acids
How is cholesterol stored?
In lipid droplets
What 2 places is cholesterol synthesised
Cytoplasm, some enzymes bound to ER membrane
What 3 compounds are required to synthesis cholesterol
AcH
NADPH
ATP
What is the function of HMG-CoA reductase
Catalyses the irreversible formatin of mevalonic acid
It is a rate limiting enzyme
What is the effect of dietary cholesterol on HMG-CoA reductase activity
It reduces its activity
What is the function of Vitamin D
Regulation of calcium and phosphorus metabolism
What is the most abundant for of vitamin D
D3
Name the 3 types of synthesised by cholesterol-steroid hormones
Corticosteroids
Androgens
Oestrogens
What is the site of corticosteroid synthesis
Adrenal cortex
What is the site of androgen synthesis
Testis
What is the site of Oestrogen synthesis
Ovary
What is the main product from cholesterol
Bile salts
What does bile act as and for what
A detergent for emulsifying ingested lipids
How is bile recycled
Enterohepatic circulation
