Explain the need for DNA packaging which condenses the DNA for cell division, but which allows expression of the DNA between divisions.
Packaging must be dynamic so that between divisions DNA is unwound enough to allow transcription but during division must be condensed enough to avoid tangling.
What is the general principles of diagnostic enzymology?
When a cell is damaged it releases its contents into blood. This will include enzymes, some of which are tissue specific and not normally present in blood so if a particular enzyme can be tested for, a knowledge of which tissue is damaged can be gained.
List factors that may cause release of intracellular enzymes.
Explain what information may be gained by assaying enzymes.
Extent of damage, more enzymatic activity=more cells affected
Describe those features of an enzyme that make it suitable for diagnostic use.
1. Can be specific to tissues.
2. If you present with its substrate then a reaction will occur
3. Do not need natural substrate- can use an artificial one that will give some sort of detectable change such as a change of colour
4. Rate of reaction proportionate to amount of damage
5. Kits readily available that allow diagnosis to be made in practice away from the lab.
Explain why enzyme activity is measured, not enzyme concentration.
Enzyme quantity may be far too small to be measured outright, measuring rate allows for a noticible reaction to occur and is proportional to the quantity of enzyme.
Name 2 enzymes that can be measured for to diagnose liver pathologies.
Describe alkaline phosphatase enzymology.
Para-nitrophenyl phosphate -> para-nitrophenolate
colourless --> yellow.
What are the advantages and disadvantages of alkaline phosphatase analysis?
AdvantagesObvious colour change
DisadvantagesAlkaline phosphatase present in re-modelling bone so can not be used in young animals
Descibe briefly aminotransferase analysis.
Transfers amino group
-present serum with alanine and a-oxoglutarate
2 stage reaction with an enzyme in kit - Lactate dehydrogenase
What reaction does lactate dehydrogenase catalyse?
NADH + H+ +pyruvate <-> NAD+ +lacate
What makes the reaction 'NADH + H+ +pyruvate <-> NAD+ +lacate' detectable?
NADH->NAD+, absorption in spectrophotometer drops
What is a disadvantage of aminotransferase analysis?