MadSci Network: Biochemistry |
Hi Hanna,
I take it you mean “vertebrates,” as in animals with spines (vertebrae are
the bones in a spine). Your hypothesis is that lager animals will have more
catalase in their livers than smaller ones, although it is not clear
whether by “more” you mean more in an absolute sense (grams or moles of
catalase total) or in the sense of concentration (grams of catalase per
gram of liver tissue). I would say that the former hypothesis is pretty
banal, since larger animals have larger livers, which probably have more of
pretty much everything than small livers. On the other hand, the latter
hypothesis could be interesting to explore. Let’s assume that your
hypothesis is that larger animals have a higher concentration of catalase
in their livers, measured in milligrams of catalase per gram of liver
tissue. Why this might be so, I don’t know, but it gives rise to an
interesting experiment at least.
To test for how much catalase is in a fixed weight of each different liver
type, I take it you plan to use the oxygen gas evolution test. That should
be fine, as long as you can be sure that each liver type was treated in the
exact same way. To the best of your ability, each liver sample should be
the same age post-mortem, should have the same temperature history
post-mortem (all frozen or all not frozen), and the catalase should be
released from the cells in each liver sample by the same method as well
(some kind of blending procedure followed by cell lysis is probably needed).
That you initially got a result indicating that the fish liver had the most
catalase could mean just that, but I can think of a couple of other factors
other than leaks that might give the same result even if some other liver
actually had a higher concentration of catalase. For example, maybe the cow
liver was not cold enough and more of its catalase degraded during storage
or transportation. Or, maybe the sheep liver actually had the highest
catalase concentration, but it also had the most active proteases, and
these chewed up a lot of the catalase during liver storage or transportation.
I would recommend conducting your experiment again with more attention paid
to removing as many extraneous, confounding variables as you reasonably
can. Such variables are probably mostly related to sample storage and
processing. Another thing to keep in mind is that catalases from different
animals may have different catalytic activities. Animal A might have lots
of a slow catalase, while animal B may have half as much of a catalase that
is twice as fast. In your assay, you might obtain a result showing equal
amounts of catalase for each animal, even though the situation is quite
different. Your oxygen evolution test is really a measure of total catalase
activity (catalase amount times catalase activity).
Finally, just in case you didn’t know, MadSci.org has a FAQ page devoted to
catalase:
http://www.madsci.org/FAQs/catalase.html
Good luck,
Alex Tobias
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