Tag Archives: white blood cells

Miracle berries and my eureka moment

Sorry this is 24 hours late, but I’ve spent a very enjoyable day down at Streatham High School, taking a look round their new labs and discussing everything from iGCSE to KS3 science. It’s always so interested and useful to visit other science departments – we should do more of it.

Anyway, what shall I burble about this week? I was quite pleased with a new idea for introducing the Nervous System to Year 13. It was inspired by one of last year’s Year 13s who gave me some experience altering tablets as a thank you present. No, not what you’re thinking. It was pack of mberry miracle fruit tablets, available for £12.50 a pop at http://mymberry.co.uk/ and featured on the Graham Norton show https://www.youtube.com/watch?v=TJwuo2Y7KXs. The protein present, miraculin, causes a conformational change to your sweet receptors such that they bind to “sour” molecules. Result – a slice of lemon tastes like lemon sherbet. I got my Year 13s to suck on a slice of lemon, and then dissolve one tablet as per instructions on their tongue, and then try the lemon again. Sensational reaction! Then get them to explain it…  Along with all the revision of receptors and proteins, it’s a really neat way of showing that our perception of the world depends entirely on which part of our brain impulses get sent to…

What else? Well, I could tell you about the amazing fun I’m having with Year 7, or share the Year 12 practical investigation into osmotic inhibition of bacterial growth, or maybe the Year 9 Martian Biologist challenge – how can you tell the difference between Eleanor and a geranium? But I want to take a trip down memory lane and share my eureka teaching moment, when I suddenly realised what it was all about.

It was my second term at St Paul’s. I was due to start the Immune System with Year 12 and I was planning my standard kind of lesson – project image of macrophage, tell them about macrophage, give out picture of macrophage, label on board, draw picture of phagocytosis, etc etc. In other words, not a lesson, but a lecture, with no active learning, just information delivery. Students all passive. Me hoping to enthuse them with the inherent brilliance of macrophages and the sheer ebullience of my teaching personality. Ahem.

And then, clearing out the filing cabinet in my lab, I found an old sheet left behind by the retiring biology teacher who I had replaced. Here it is.

The Immune System

Natural Immunity

In mammals, non-specific or natural immunity operates partly through PHAGOCYTIC white blood cells (leucocytes).

  1. Observe a prepared slide of a blood smear. Using an Atlas of Histology and Biology textbooks to help you, identify and draw labelled diagrams of a phagocyte and a lymphocyte.

Add to your diagrams the mean diameter for each type of white blood cell (in mm) and a concise description of the cell’s appearance.

2)        Draw annotated diagrams to illustrate the mode of action of a phagocyte.

From where are phagocytes derived?

What are the two main types of phagocyte? How may they be distinguished?

It doesn’t look like much. No fancy formatting or sexy SEM images or even a joke or two. But the lack of frippery probably helped me “get it”. And it was so simple! I just needed to step away from the white board, put down the marker pen, and stop talking. I needed to tell the students as little as possible. Quite the opposite. I needed to let them find out for themselves. Make them do all the work. Base it around practical observation or investigation. Make it a journey of discovery. Make it active learning. My job was to guide and enable, not just tell them stuff. It came as a revelation, though in fairness to my brilliant PGCE teachers, it was basically what they had tried to tell us during the teacher training course.

So why hadn’t I got it earlier? The fear, I think, is in letting go, relinquishing control of the class, because as long as they’re looking at me and copying stuff off the board, I’m doing my job and it’s all nice and safe. The only down side is that, underneath all the busy scratching of pens, the students are bored and not actually learning anything….

Anyway, I’ve modified this leucocyte activity a bit now – in fact, I use a simplified version with Year 11 to put some practical activity into what can become a very theory heavy topic. I basically just give them the blood smear and a microscope. I tell them to find the blood cells (a challenge, coz they’re so small, but they can do it!), and then to find the ones with purple inside them. Draw them. Draw them large (half a page each). Label as much as you can. What’s the purple stuff? How can you tell? And so on. They love the challenge, the variety, the element of the unknown, the discovery…

Ugh. 8 period day tomorrow, just to round the week off nicely. Good news, I end it with Year 7 fully indulging their pyromaniac tendencies!

Ta ra.