Skildum: Liver Biochemistry 2 Flashcards
From what and when does the liver synthesize ketone bodies?
Ketone bodies are synthesized from FATTY ACIDS during EXTENDED FASTING/ starvation.
Why is it important for the liver to synthesize ketone bodies during periods of extended fasting/starvation?
Ketone bodies serve as an ALTERNATIVE FUEL SOURCE to reserve glucose for tissues that are dependent on it, e.g. red blood cells.
How does the liver synthesize nucleotides?
Uses blood AA to form purines, pyrimidines, heme, NTs, hormones, and other functional N products.
Why does the liver have a high requirement for products of the PPP?
NADPH powers biosynthetic and detoxification reactions.
Nucleotides are used for nucleic acids and cofactors.
What are some proteins that are synthesized in the liver (modified by branched sugar chains)?
Blood coagulation proteins
Metal-binding proteins
Lipid transport proteins
Albumin
Where does glycosylation of glycoproteins and proteoglycans occur? What does the chain begin assembly on?
Lumen of the endoplasmic reticulum.
a molecule of dolichol
How is the glycosyl chain formed?
transferred from dolichol to the protein>
modified further as it is transferred through the Golgi
Hepatopathy Bifid uvula Growth retardation Myopathy Hypoglycemia Dilated cardiomyopathy
Are associated w/ what gene mutation?
homozygous PGM1 mutations
What does PGM1 do?
interconverts glucose 1-phosphate and glucose 6-phosphate
What is PGM1 essential for?
glycogenolysis
glyocogen synthesis.
important for generating UDP-galactose, a glycosylation intermediate.
What does transferrin do?
Transports ferric iron (Fe3+) from the intestine to the liver.
*glycosylated at 2 sites
Pts w/ PGM1 muts have defects in what type of glycosylation?
transferrin glycosylation
What supplement can increase the glycosylation of transferrin?
galactose supplementation
also helps to resolve sxs of: Rhabdomyolysis resolved & cardiac function improved Hypogonadotropic hypogonadism resolved Leuteneizing hormone increased Puberty initiated
Why is glycosylation of leutenizing hormone (LH) important?
It stabilizes it in circulation and increases its affinity for its receptor
What detects liver damage?
increase in conjugated + unconjugated serum bilirubin
What detects hemolysis?
increase in unconjugated serum bilirubin
What lab may indicate urea cycle problems?
serum ammonia
What can an elevated bilirubin indicate?
increased red cell breakdown or decreased conjugating capacity in the liver
What is the difference between direct and indirect bilirubin?
conjugated vs unconjugated
BIlirubin is glycosylated in the liver by adding UDP glucuronate to form bilirubin diglucuronide. What catalyzes this reaction?
glucuronosyl transferase
Why is it important to form bilirubin diglucuronide?
more soluble and can be excreted in the bile or urine
What is the rate limiting step in bilirubin elimination?
transport across the canilicular membrane
What enzyme test is the most specific for liver damage?
ALT
AST:ALT <1 suggests…..
ACUTE hepatocellular damage
AST:ALT >2 suggests…
Liver damage secondary to alcohol abuse
What enzyme tests detect cholestasis (bile duct blockage)?
alkaline phosphatase
5’ nucleotidase
gamma-glutamyltranspeptidase
Where is alkaline phosphatase located?
localized to canilicular membrane of hepatocytes
NOT specific for cholestasis (or liver disease)
Where is 5’ nucleotidase located?
localize to canilicular membrane of hepatocytes
Where is gamma-glutamyltranspeptidase located?
localized in bile duct epithelial cells
What tests measure the liver’s biosynthetic capacity (proteins made by the liver)?
Serum albumin
serum globulins
coagulation cofactors
What liver protein has a long half life (so it is not good for acute liver damage) and if
decreased may reflect malnutrition rather than liver disease?
Serum albumin
What produces serum globulins?
B lymphocytes (gamma-globulin) and hepatocytes (alpha and beta globulins)
Why do gamma globulins increase w/ liver disease?
increased antigenic material circulating in the hepatic circulation
What is indicative of alcoholic liver disease?
increased IgA
What liver disease is indicated by increased IgG?
Autoimmune hepatitis
What liver disease is indicated by increased IgM?
primary biliary cirrhosis
An elevated pTT suggests ….
defect in synthesizing fibrinogen in the liver
