Exam II Study Guide
Supplement
Selected Discussion Topic Answers
- Fructose intolerance:
- What is the deficiency in this case?
- The patient is missing the aldolase activity which splits
F-1-P.
- Describe the cascade of effects from this defect which can
eventually lead to cell death, explaining how this single defect
can have such a severe impact.
- F-1-P builds up, tying up inorganic Pi.
- Lack of Pi prevents cell from regenerating
ATP from ADP,
- Lack of Pi also prevents breakdown of glycogen
by Pase, leading to hypoglycemia and thus poor fructose tolerence
test
- Low [ATP] slows ion pumps, preventing cell from maintianing
sodium/potassium gradient etc. Eventually osmotic imbalance results
in loss of membrane integrity, leakage and cell death.
- Why are SGOT & SGPT elevated in this case study?
- Loss of membrane integrity and leakage releases these
enzymes from liver parenchymal cells into serum.
- Galactosemia:
- What two enzyme deficiencies can lead to galactosemia?
- Kinase and uridyl transferase.
- Which is more severe? Why?
- The uridyl transfease because there will be a build-up
of the Gal-1-P, tying up Pi.
- Which has a similar effect to the Fructosuria above? Why?
- The uridyl transfease because there will be a build-up
of the Gal-1-P, tying up Pi.
- Would a mother who is homozygous for galactosemia be able
to produce lactose in her milk? Explain.
- Yes, if she has the epimerase she can still convert UDPG
(as is formed for glycogen synthesis) to UDPGal which is the
activated form of galactose for lactose synthesis.
Last modified 30 March 2012
