Category: Teaching

Hairy kneecap

Euplotes patella [CC-BY-SA-4.0 Yikai Feng]

Our microscopy practical always turns up something new, which is the main reason I enjoy it. This year it was a ciliate called Euplotes patella. This kneecap-shaped critter is a single-celled organism masquerading as a tiny animal. The appendages that look like long hairs or legs are bundles of extra-long cilia called cirri, which it …

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Euchlanis rotifer [CC-BY-SA-3.0]

Most years the pond-water microscopy practical throws up an exciting ciliate (or two, or three), but this year, the only ones we saw were duplicates, or too bloody fast to photograph. Ho hum. So this year you’ll have to make do with an imposter. It’s still got cilia, but it is not a ciliate, and although it’s no bigger …

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A graph to show

A graph to show [CC-BY-SA-3.0 Steve Cook]

I’ve never been sure where “a graph to show…” comes from. As far as I can tell, A-level specifications don’t use or specify this wording, and you wouldn’t typically see it in a figure legend in a scientific paper. But if you ask first-year students to put a title on a graph without any further guidance, almost every one of them will default …

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Phage vs. host

Phage vs. host [CC-BY-SA-4.0 Steve Cook]

For a recent schools’ outreach day, I put together a card-game based around the arms-races that develop between bacterial hosts and their viruses (bacteriophages). It’s mostly just a bit of fun, but if anyone finds it useful or can suggest improvements (or just make them! I release this under a CC-BY-SA-4.0 license) I’d be happy to hear them.


Stentor sp. [CC-BY-SA-3.0 Steve Cook]

We had the annual “looking at muck down a microscope” practical last week. As usual, the best thing we saw was a ciliate in some pond water, in this case a little trumpet animalcule: Previous winners: Vorticella and Lacrymaria. The Ciliata really are the phylum that keeps on giving.

Teardrops of the swan

Lacrymaria olor [CC-BY-SA-3.0 Steve Cook]

Last year, the most marvellous thing we saw in the pond-water microscopy practical was a ciliate, and this year the prize goes to that same clade. Ciliates don’t disappoint. This is Lacrymaria olor, the “teardrop of the swan”. It’s a predator, like the Vorticella from last year, but rather than sitting rooted to the spot, Lacrymaria is …

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The Wason card problem

Wason cards [CC-BY-SA-3.0 Steve Cook]

The Wason card problem is a well-known psychological test that probes how people think about hypothesis testing. The version I use in one of my first-year lectures is shown below. I think the original version used letters and numbers, but I’m a biologist, so obviously I use pictures of dead pets instead of numbers. We …

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Enzymes provide alternative routes to product with a lower activation energy

Maxwell Boltzmann distribution [CC-BY-SA-3.0 Steve Cook]

An enzyme lowers the activation energy for a reaction Like a previous post, the problem here is not so much that this idea is flat-out wrong, but that it’s very prone to misinterpretation. Text-books often state that an enzyme, or any other catalyst, lowers the activation energy of a reaction. The activation energy for a reaction (written …

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The Michaelis-Menten model is not applicable to most enzymes in a cell

Sigmoidal kinetics [CC-BY-SA-3.0 Steve Cook]

Enzymes in cells can be modelled using the Michaelis-Menten model Enzymes can be, and often are, modelled by the Michaelis-Menten (well, Briggs-Haldane) model: v = vmax · [S] / (KM + [S]) Where: v is the velocity of the enzyme, which is the rate at which product accumulates vmax is the maximum velocity of the enzyme (i.e. …

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Metabolic pathways don’t really have end products

M1 motorway map [CC-BY-SA-3.0 Steve Cook, based on uncopyrighted image by Michiel1972]

The end product of glycolysis is pyruvate This, and equivalent statements about other metabolic pathways: The products of Krebs cycle are ATP/GTP, NADH and carbon dioxide are not exactly wrong, but they are easily over-interpreted in a way that leads to misunderstanding. They are also  easily swallowed as explanations without considering quite what ‘end product’ …

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