The S204 potato experiment

I have finally gotten around to completing this which “just” leaves the writing up to be done.

Home experiments used to be all the rage in the Open University science courses but they seem not to be so popular these days or at least not on such a widespread basis. That’s not to say they’re not around in significant numbers on some courses though: last years Astronomy (S282) course came with loads of them. For the biology course there are two experimental weeks although in reality it’s more like a couple of experimental days if the first one is anything to go by.

The problem of course is all the health and safety considerations that come to bear on these things nowadays. What’s particularly odd about the biology experiment is that step one is to acquire a chemical that is one of three components that are very popular with bomb makers: something that has caused some difficulty in purchasing said item for a number of students.

The potato experiment comes in three segments. In the first segment we’d to try a pilot experiment with our liquidised potato and hydrogen peroxide to select a suitable concentration of liquidised potato to use in the later experiments. All by itself that part took over an hour for me and I ended up having to repeat it as the catalase in the potato went off mid-way through the second experiment.

The second experiment takes even longer. Despite having got into the swing of it, that one ended up taking several hours which is where the problem in my first attempt lay as the catalase goes off in around three hours so having the mid-point falling at close to that time was asking for trouble. The objective of that one is to find the period when the catalase is working at its peak rate which almost always is going to fall in the first minute so it makes for a very boring 9 minutes for each of the five replicates that you’ve to run.

In the final experiment you get down to the meat of the experiment which is to show that the reaction rate is dependent on the concentration of the catalase which takes another couple of hours.

Add up all the experiment times and you’re looking at around six hours to complete this. And then you have to do some statistical work and write up the experiment.

As in last years SXR270 glucose assay, the problem with this experiment is that you need to do so many replicates that it gets to be very mechanical and boring which doesn’t seem right given that what you’re working on comes with some really interesting theory behind it.

We meet the potatoes again in August when we’ve to devise our own experiment. The devising of it is what needs most thought unless you have a commercial laboratory handy. Thus, things like examining the effect of different temperatures are complicated unless you choose 0C and whatever the room temperature is but even then it’s not so simple as the liquidised potato needs to be kept in the fridge ie you only really vary the temperature of the water you’re diluting it with. Comparing how it works in the light and dark would be nice to do but doesn’t seem practical and neither does varying the colour of the light. Varying the pH would also be nice to do and certainly possible but how would you measure the pH without laboratory equipment? You could even compare different ages of potato but that’s complicated in that you’d need to use the same variety of potato and you don’t know its age (unless you’ve grown it yourself…hmmm).

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