Metabolic Functions Of The Liver Flashcards
What does the liver protect in the body
This means the liver protects the major vessels from direct contact with the
newly absorbed contents from the gut.
Where does the liver empty into
The liver empties directly into the major vessel entering the
heart (inferior vena cava) that ensures rapid circulation of its products
Where do the bile ducts come from and what do they empty into
The bile ducts coming from
the liver and gall bladder empty directly into the gut meaning the liver can rapidly influence
digestion.
How does liver regulate glucose conc
The liver plays a central role in regulating circulating glucose concentration levels. When there is
excess glucose, it stores glucose in the short-term as glycogen, and in the long term as triglycerides
that are moved to muscle or adipose tissue. The liver also releases glucose into circulation from
these stores through gluconeogenesis and glycogenolysis when circulating glucose levels are low. In
fact, the liver regulates the level to which these different pathways take place at in response to levels
of glucose in the blood.
How is the liver able to metabolise proteins and amino acids - what are the biproducts
The liver also plays an important role in the metabolism of proteins and amino acids. The liver
degrades excess amino acids through gluconeogenesis to make sugars and ketone bodies depending
on if the amino acid is glucogenic or ketogenic. The bioproducts of these reactions include ammonia
and the liver is the major site for transamination and deamination of amino acids and detoxifying the
resulting ammonia into urea.
What other proteins are synthesised in the liver
Many serum proteins are also synthesised in the liver including albumin
as well as some clotting factors.
Describe how the liver does fatty acid synthesis
The liver also plays a central role in fatty acid synthesis and degradation. Synthesis takes place in the
cytosol of hepatocytes whilst the breakdown occurs in the mitochondria of hepatocytes in a process
known as beta-oxidation. The transport of lipids and the maintenance of circulating lipid levels are
also function of the liver through different lipid molecules like VLDLs, LDLs and HDLs. The HDLs are in
fact important in clearing up the debris left by dead cells.
What is the liver also able to synthesis - describe the princess
The liver also synthesises around 50% of
the cholesterol in the body (remainder formed by the intestine, adrenal cortex and reproductive
tissue). This process begins from an acetyl CoA molecule that undergoes a series of reactions
controlled by the rate limiting enzyme HMG-CoA reductase. The cholesterol formed is then
transported from the liver by VLDL.
What happens to excess cholesterol in the body
Excess cholesterol cannot be broken down but is instead excreted
through the biliary system either as cholesterol or as bile acids and salts.
The liver plays a central role in metabolism of many nutrients
What are the 5 things the liver does
Regulation of carbohydrate metabolism
– To maintain blood glucose • Regulation of fat metabolism
– synthesis
– β-oxidation • Regulation of protein metabolism
– Plasma protein synthesis
– Detoxification of ammonia - Urea formation • Cholesterol synthesis and excretion • Synthesis of specialized molecules
– bile acids
– haemin
Describe what vessels empty out into from the liver
receives blood from the
gastrointestinal tract via the portal
vein
delivers major dietary nutrients protein, carbohydrates but not lipids
also delivers drugs and potential
toxins • Empties directly into major vessel
entering the heart.
Ensure rapid circulation of its products.
• Bile ducts empty directly into gut.
Can rapidly influence the digestive
process
What are the 2 routes of ethanol
There are two routes to the metabolism of
ethanol
– Oxidation through the activity of alcohol
dehydrogenase
90% – Microsomal oxidation using cytochrome P450
10-20%
Describe the micro Somali ethanol - oxidizing system MESO
MESO is the second route of ethanol metabolism
• Involves the oxidation of ethanol by members of the
cytochrome P450 family of enzymes.
• The pathway generates acetaldehyde
• As this system consumes NADPH required for the
synthesis of the antioxidant glutathione it results in
increased oxidative stress
Describe acetylaldehyde
Is highly reactive and can accumulate with excessive
ethanol intake
• Acetaldehyde is very reactive and can inhibit enzyme
function.
• In the liver this can lead to a reduction in the secretion of
both serum protein and VLDL
• Can also enhance free-radical production – leading to
tissue damage such as inflammation and necrosis
What are the stages of liver damage
Three stages of alcohol liver damage
• Stage 1: Fatty liver
• Stage 2: alcoholic hepatitis, groups of cells
die resulting in inflammation
• Stage 3: Cirrhosis which includes fibrosis,
scaring and cell death
• As the cirrhotic liver cannot function
properly ammonia will accumulate resulting
in neurotoxicity, coma and death
• Cirrhosis arises in 25% of alcoholics and
75% all cirrhosis is due to alcohol
