Biochem of the Liver Flashcards
where does the liver excrete unwanted molecules
into biliary tree and faecal excretion
name a plasma protein
albumin
why is faeces white in end stage liver disease
as liver not breaking down haem into bilirubin
how does the liver regulate metabolism
fuel storage- carbohydrate and lipid metabolism
urea cycle- amino acid metabolism
what does electrophoresis do
separates proteins by size
name the different plasma proteins
albumin, alpha gamma and beta globulins (gamma globlins= immunoglobulins)
what colour is plasma
straw coloured
what are the main functions of plasma proteins
maintain oncotic or collois osmotic pressure (maintains fluid balance across vessels walls)
transports hydrophobic substances
pH buffering
enzymatic
immunity
what hydrophobic substances do plasma proteins transport
steroid hormones, free fatty acids, bilirubin, cholesterol
give an example of the enzymatic actions of plasma proteins
blood clotting
what does albumin do
controls oncotic pressure ans transports hydrophobic substances
what do alpha globulins do (e.g ceruloplasmin)
transport lipoproteins, lipids, hormones and bilirubin
is a retinal binding protein , transports vitamin A
what does a deficiency in vitamin A cause
visual impairment
name two beta globulins and their functions
transferrin- transports Fe3+, indicator of iron deficiency
fibrinogen- inactive form of fibrin, clotting of blood
what is the most abundant plasma protein
albumin
what stimulates the production of albumin
insulin and nutrient intake
when are albumin levels low
liver disease or starvation
what is albumins affinity and capacity for hydrophobic molecules
low affinity but high capacity
what endogenous lipophilic substances does albumin transport
fatty acids, bilirubin, thyroid hormone
what exogenous substances does albumin transport
drugs with weak hydrophobic capacity e.g. aspirin
where is iron stored
in cells bound to ferritin
why is iron important
component of haemoglobin, myoglobin, cytochromes
what in the blood transports copper
ceruloplasmin
what does a deficiency in ceruloplasmin result in
wilsons disease
what are steroid hormones derived from
cholesterol
which steroid hormones are hydrophobic
T3/4
how are steroid hormones transported in the circulation
via transport molecules
- thyroxine bound to thyroid-binding globulin
- cortisol bound to cortisol-binding globulin
why are transport molecules essential for steroid hormones
as would be eliminated by liver or kidney without them
describe the structure of a lipoprotein
core of hydrophobic lipids (cholesterol esters, triglycerides)
surrounded by a shell of polar lipids (phospholipids) and apoproteins
what is the role of lipoproteins
fat and cholesterol transport between organs and tissues
what is the function oh HDL
reverse cholesterol transport- removes excess cholesterol from cells (cholesterol esterified with fatty acids, transported back to liver, excreted as bile salts via biliary tree of faeces)
what is the only organ capable of metabolising and excreting cholesterol
the liver
what vitamins does the liver store
A, D and B12
where does iron stored in the liver come from
haemoglobin
what does cholesterol do to cell membranes
increases rigidity- good thing
what is cholesterol pre cursors of
bile acids, steroid hormones, vit D
is cholesterol soluble in water
no- especially if esterified to a long chain fatty acid
how is cholesterol solubilised
via incorporation into lipoproteins- located in core of molecule
where is the main site of cholesterol synthesis
liver
what does HMG-CoA reductase
catalyses the irreversible formation of mevalonic acid- rate limiting enzyme in cholesterol synthesis
what increases and reduces the activity of HMG-CoA reductase and therefore the synthesisi of cholesterol
increased by fasting
decreased by dietary cholesterol
also controlled by hormones
what is the role of vit D (a product from cholesterol)
regulation of calcium and phosphorus metabolism
what steroid hormones are made from cholesterol
corticosteroids
androgens
astrogens
what organ makes each steroid hormones from cholesterol
corticosteroids- adrenal cortex
androgens- testis
estrogens- ovary
what is the main metabolic product from cholesterol
bile salts
where are bile salts synthesised and secreted from
the liver
where are bile salts stored
in gall bladder as component of bile
how are bile salts recycled
by the enterohepatic circulation
what do anion exchange resins do and how does it affect cholesterol
bind bile salts and inhibit re-absorption in the enterohepatic circulation- increased synthesis and excretion, conversion of cholestrol in the liver is decreased, uptake of LDL is increased as numbers of LDL receptors increased= lower plasma LDL
