Metabolic Functions of the Liver Flashcards
(50 cards)
How does the liver decrease Blood glucose levels?
By regulating flux into the pathways that remove free glucose, the liver contributes to lowering BGL
How do other organs contribute to lowering BGL?
Other organs (adipose tissue and muscle) also switch on their biosynthetic pathways to remove glucose from the blood
How does the liver maintain constant BGL?
- Removal of glucose from blood post meal
- Storing glucose as glycogen
- Restoring BGL via gluconeogenesis + glycogenolysis
- Regulating fluxes through glycolysis, pentose phosphate
cycle + gluconeogenesis
Which sugars does the liver metabolise?
The liver is involved in metabolism of other sugars e.g. fructose and galactose as well as glucose
What role does the liver play in protein synthesis?
The liver is the major site for serum protein synthesis
e.g. albumin and blood clotting factors
What is the fate of excess amino acids in the body?
The liver degrades excess amino acids especially during gluconeogenesis
What are glucogenic amino acids degraded into?
glucogenic amino acids → sugars
What are ketogenic amino acids degraded into?
ketogenic amino acids → ketone bodies
What role does the liver play in the removal of toxic ammonia?
Major site for transamination + deamination of amino acids and detoxification of ammonia
What is the significance of liver interaction with muscle?
Important in regulating BGL available to tissues
Important in converting metabolites → proteins / sources of energy
How does the liver regulate fats and lipids in the body?
The liver also plays a central role in the synthesis, transport and metabolism of lipids and fats
How does cholesterol enter the livers cholesterol pool?
- dietary
- de novo via extra-hepatic tissue
- endogenous (own production)
Where is the body’s cholesterol made from?
50% cholesterol made by liver
rest produced by intestine, adrenal cortex, and reproductive tissue
Made from acetyl coA (HMG CoA reductase)
Transported from liver as VLDL
How is cholesterol excreted from the body?
Body can’t degrade cholesterol
Disposed by biliary system in intestines as either cholesterol following conversion to bile acids/salts
Why is ethanol metabolism significant?
Need to metabolise ethanol as its present as a consequence of either diet or lifestyle
What are the 2 routes of ethanol metabolism?
- Oxidation (via alcohol dehydrogenase)
2. Microsomal Oxidation (via cytochrome p450)
Outline the metabolism of ethanol
ethanol → acetaldehyde →acetate
using enzymes alochol and actealdehyde dehydrogenases
What is the consequence of methanol metabolism?
Methanol→formaldehyde - v. toxic
associated with paralysis, loss of consciousness and blindness
Explain how certain ethnicities are intolerant to ethanol
40% of asians are intolerant to ethanol showing symptoms of:
- tachycardia, facial flush, vasodilation and nausea
What are the products of ethanol metabolism?
Oxidation of alcohol takes precedent over other nutrients and isn’t regulated by negative feedback so large quantities of NADH, ATP and acetyl CoA are formed
- can cause inhibition of certain metabolic pathways
Which pathways are inhibited due to ethanol metabolism?
Acetyl CoA, NADH + ATP
- inhibit glucose metabolism by inhibiting PFK + pyruvate
dehydrogenase
NADH
- inhibits tca cycle + acetyl CoA increases further
Acetyl CoA
- Causes ketone body formation + FA synthesis
stimulation
- FA esterified to TG for VLDL export
What does MESO stand for?
Microsomal Ethanol Oxidising System
What is MESO?
2nd route of metabolism
involves oxidation of ethanol by cytochrome P450 family
uses NADPH required for GSH synthesis
Outline features of acetaldehyde
- highly reactive (accumulates w/ excessive alcohol)
- can inhibit enzyme functions
- liver leads to reduce serum protein and VLDL secretion
- Can enhance free radical production →leads to tissue
damage e.g. inflammation + necrosis
