Liver Flashcards
Why are pharmacologically active compounds lipophilic?
To be able to pass through plasma membranes to reach metabolising enzymes.
Are phase I or phase II reactions known as ‘functionalisation’?
Phase 1
Which ion do cytochrome p450 enzymes use to oxidise substances?
Fe2+
What is the overall equation for the reaction that occurs at a CYP enzyme in a type I drug metabolism reaction?
NADPH + H+ + O2 + R-H —> NADP+ + H2O + R-OH
Which phase (I or II) of drug metabolism is non-synthetic catabolic?
Phase I
Which phase (I or II) of drug metabolism is synthetic anabolic?
Phase II
What is UGT?
glucuronosyltransferase
What is UDPGA?
A co-enzyme/donor compound required to conjugate glucuronic acid.
What is formed in a paracetamol overdose?
How is this substance formed?
NAPQI
Produced when stores of glucuronic acid and sulphate are not sufficient to conjugate all the paracetamol.
Instead the paracetamol is oxidised.
What is the role of ADH (alcohol dehydrogenase)?
Converts ethanol to acetaldehyde.
What is the role of ALDH (aldehyde dehydrogenase)?
Converts acetaldehyde to acetate (in alcohol metabolism).
What is acetate converted into in alcohol metabolism?
CO2 and H2O
How is the absorption of iron controlled?
Active absorption in the duodenum responds to negative feedback.
What happens when there is sufficient concentrations of free iron in the blood?
Increased transcription of the gene coding for ferritin.
What happens when the concentration of free iron in the blood is low?
Production of ferritin decreases so unbound iron increases.
What protein binds iron in the blood?
Transferrin
How is iron stored in the body?
Bound in ferritin in liver kupffer cells.
How is iron mostly excreted?
It is stored in ferritin in intestinal epithelial cells, and is released to be excreted when cells at the tips of the villi disintegrate.
What are the four starling forces?
Capillary hydrostatic pressure
Interstitial hydrostatic pressure
Osmotic force due to plasma protein concentration (capillary oncotic pressure)
Osmotic force due to interstitial fluid protein
Which clotting factors are not produced in the liver?
Calcium (IV) and von Willebrand Factor (VIII)
What is a complement factor?
A plasma protein which sticks to pathogens and is recognised by neutrophils.
Helps mark pathogens to kill.
Briefly describe the lysosomal pathway of protein degradation.
Carried out in reticuloendothelial system of the liver (sinusoidal epithelial cells, Kupffer cells, & pit cells).
Sinusoidal epithelial cells remove soluble proteins from the blood.
Proteins fused with lysosomes which contain lysosomal enzymes.
Kupffer cells work similarly but they phagocytose particulate matter.
Briefly describe the Ubiquitin-Proteasome Pathway of protein degradation.
Degradation is a selective process.
Proteins targeted for degradation by attachment of ubiquitin peptide.
Peptide directs protein to complex called a proteasome.
Proteasome unfolds and breaks down protein.
Define catabolism.
Breakdown of complex substances into simpler ones accompanied by the release of energy.
