Monthly Archives: November 2015

Snot trafficking

Again, no major theme or single lesson this week. Just continuing to throw a few random ideas out.

And back to i-pads and apps and Cell Ultrastucture. TEM exercise updated and scanned June 2014I’ve always done it like this – even if they just need information, it’s better for them to be reading and processing and using the information, rather than just copying it down. But this exercise has been transformed by the i-cell app


which allows them to not only see all the structures in helpfully colour coded 3D, but to spin them, manipulate them, zoom in on them…

I quickly follow this with “Snot Trafficking” Protein trafficking new for 2014 Sept which I link to the splendid John Kyrk animation, so that they can see how all the organelles interact. A clip from Secret Life of Cell showing Kinesin in action on the cytoskeleton illustrates how transport vesicles are moved (and brings in the role of the Mitochondria). These superb clips of vesicles moving in real time is another vivid punctuation mark in their activity.

They will find this difficult. This year I livened it up by turning the lab into a cell. Starting in one corner with the festive DNA model


I modelled the copying of the message (just a note on a post it – green, red, blue, red, green, yellow, blue etc) passed on to a student playing a ribosome with a large pile of coloured chunky lego (amino acids) which she had to join together in the order specified.

The finished lego polypeptide is put into a tray (a transport vesicle) and moves to the next desk (the first layer of the Golgi). On the desk, more students add post-its (carbohydrate chains) before putting it into another “vesicle” and shuffled on to the next desk. I made loud squelching noises to illustrate the budding and fusing of the vesicles from one desk to the next.

The final desk is linked to the Fire Exit by a bit of string – and I walk the tray along it to the door which I then open and throw the lego out of the lab with a flourish (they really liked this bit).

The resulting A3 posters were superb as they threw themselves into the detail…

And Year 13 and muscles.

As a springboard into micro-fibrils, try giving them an Electron Micrograph of muscle tissue (unlabelled) and ask them to draw it. They will produce a beautiful observational drawing of a sarcomere without having any idea of what it is. Ask them to describe it. How could this work? They’re half way towards the sliding filament model which, once they’ve figured it out, they can then make a working model of ….


My brilliant colleague

Year 10 respiration.

I’m not teaching KS4 at the moment, so I’m not really thinking about Year 9-11 lessons these days. But when a colleague told me what she’d been doing with her Year 10s, I just had to report it here. Her approach was brilliantly simple.

So, she said to the class, what’s the equation for aerobic respiration?

They dutifully parroted the glucose plus oxygen goes to carbon dioxide and water routine.

And respiration is one of the….?

(parrot): Life processes.

So it only occurs in….?

(parrot): Living things (like parrots).

And then she socked it to them.

How do you know?

Blank looks.

How do you know?

(hesitant). Because you told us?

But why believe me? Just because I’m a teacher? An authority figure? That’s not how science works!

Pause for effect….

Prove it.


Go on, prove the statement. Living things take glucose and oxygen and produce carbon dioxide and water. Show me that it’s true.

And that was it. She didn’t tell them how. She didn’t give them a method or a plan. She just provided standard lab apparatus plus a few other things, including methylene blue, balloons, lime water and yeast in suspension.

It was joyous. Set free from the constraints of a set protocol, they threw themselves into the problem and solved it in a variety of ingenious ways.

I’ll post photographs of their results as soon as I have some, but it was one of those lessons where you wish an Inspector had just happened to drop into.

Year 12 Immunology

Burble follower Nicola has asked how I start Immunology with Year 12.

I base most of my Immunology teaching on Lauren Sompayrac’s brilliant book, How the Immune System Works – indeed, I shamelessly steal most of his ideas and analogies, including this one.

It’s a lesson that is largely chalk and talk – though with lots of opportunity for questions and discussion. It’s such an inherently interesting topic that they stay focussed throughout. I always try and push the detail as far as possible, because it is so much more beautifully elaborate and complicated and sophisticated than they can possibly imagine. I also like to characterise the cells – macrophages as the general garbage collectors who can be upgraded to vicious killers. The visigoth neutrophils who just “kill things and break stuff”.

So I ask the students to compare their body to a fortress, or castle. How will they keep out the invading barbarian forces?

So they get the idea of a huge perimeter defended by an impenetrable wall (skin).

But there have to be gaps in the wall to allow supplies into and out of the castle (digestive/respiratory/reproductive systems) – and compare 2m2 of skin with 400m2 of mucus membranes!

How to defend this?

So the idea of more basic defences – boiling oil perhaps representing mucus, acid, lysozyme, earwax….

But what happens when there’s a break in the perimeter barrier? A trebuchet bashes a hole in the wall, you cut yourself…

So we talk about the impossibility of defending every inch of the perimeter with sufficient forces. What would you want instead?

They quickly suggest sentries. Aha, meet the macrophages. Patrolling the tissues.

And when the perimeter is broken, what would you want a good sentry to do?

Send for back up! And fight the invaders until help arrives.

Sending for back up allows us to review/revise cytokines and cell signalling.

And with the back up you’re talking about the 20,000,000,000 neutrophils circulating in the blood. Why is it a good idea for them to circulate in the blood? I describe the slow, sniff, roll, exit behaviour of neutrophils in response to macrophage cytokines. It’s just all so cool!!!!

I tell them about the biggest ball of pus I ever saw, rolling slowly down the shin of my then girlfriend Louise, following an infected mosquito bite in Uganda. A huge ball of… dead neutrophils. Why is it important for neutrophils to be short lived?

And so on.

I’ve attached my PP illustrating antigen presentation Immune response (imagine that lymph glands are singles bars with 1000s of lonely B-cells being constantly introduced to potential antigens, hoping to meet their perfect match..) and clonal selection/expansion. Bit primitive, but it works. And my exercise for them to annotate and explain.clonal expansion summary

Hope this helps!


PS don’t forget to talk about breast feeding and the importance of kissing your baby! the idea that you sample the antigens around your baby’s mouth, quickly make the relevant antibodies, and ship them into the breast milk will astonish, amaze and intrigue them.Natural Passive Immunity mum’s milk

Random odds and ends

No major theme or single lesson this week, just a few  random ideas that I’ve used in lessons this week, either as introductions or illustrations, part of the essential punctuation of any lesson plan to prompt thinking, help clarify or just provide some variation.

Year 13 and Hox Genes…

This follows their investigation into the Lac Operon (which worked beautifully this year – just fabulous results – see 25th Sptember 2014). With no introduction, I start the lesson with this Mitchell and Webb sketch.  After the initial shock and hilarity, ask the question – what is the serious underlying point here? Why don’t people grow buttocks on their heads? (or 19 penises for that matter, if you decide to show the next clip in the sequence). The genes for buttock formation are all there in the cells of your head. Why is it a head at all, and not, say, an arm? Sounds silly? Show some pictures of fruit flies growing legs out of their faces and eyes at the end of their legs. Hox genes for blog I’ve also included a little animation to illustrate the point that these genes are exactly the same in all animals. So a hox gene taken from a fruit fly will perform exactly the same job in a mouse. Or a shark. Or a chicken. Or you…

Year 12 and Potato Osmosis….

…and trying to push them beyond the simple explanation of mass gain vs mass loss as a result of water potential gradients (which they should have been able to do in Year 9). I want them to explain the whole shape of the graph. They look confused. What does this mean? It can take them a while to see what I’m getting at as I push for a more rigorous description, but the question is, why does it lose more and more mass as the sugar concentration increases? And why does it start to level out at the highest sugar concentrations?

Going from the abstraction of the graph to the specifics of potato tissue is not easy, and one class was clearly struggling, so I turned to a trusty balloon to help them visualise it and make the link.

Sketch the graph on the board. Inflate a balloon. Balloon = potato cell. Air = water. All clear?


Move it along the line – sugar concentration has gone up – water potential difference is greater – what happens? Let a little air out of the balloon.


Move it further along. What happens? Let a little more air out.


By the time you get to the plateau, there’s no air left to come out – the mass of the balloon/cells won’t change much.


They liked this. Hope you do too.

Playing God? It’s un-natural!

As I’ve mentioned before, I’m a huge fan of role play in Science Lessons (see e.g. Enzymes and Immigration: Feb 11th 2015). Apart from anything else, it’s a great way of introducing an element of variety into your lessons. I like to see students arriving at the lab early asking, “what are we doing today?” Shows they don’t know what to expect, shows that your teaching isn’t becoming predictable…

From an educational perspective, role play can help in visualising biological processes, getting them to actually imagine what’s going on in the test tube/blood vessel/sperm duct, but it can help in other ways too.

I used to really dislike class discussions on the ethics of Biotechnology. In particular, I would get terribly frustrated by the apparent lack of imagination shown by students when asked to comment on the ethics of some aspect of biotechnology. Perhaps it says something about the quality of teaching they have in this area, but it’s depressing to see the inevitable kneejerk response:

Cloning? It’s Bad. Why? It’s unnatural…

Embryo selection? That’s Bad too. Why? It’s playing God…

Genetic modification? That’s Really Bad. Why? It’s playing God AND it’s unnatural….

I find these answers depressing because it shows they’re not actually thinking (it also shows they don’t understand what “ethical” means).

I used to counter this by trying to ridicule the response.

Smallpox? Bad? But why? It’s natural…

Kidney dialysis? Good? But why? It’s playing God…

I’d say things like, “quick! Turn off the lights and take off your clothes – they’re un-natural!”

But I came to realise that these were just cheap shots that weren’t helping the students think beyond their knee-jerk responses – they just ended up confused or frustrated. Even if they took the point on board, they still couldn’t formulate an intelligent, nuanced response to any generalised point and GCSE questions asking for possible ethical objections to cloning Dolly the Sheep would still be met with this dull, unthinking response. Or some nonsense about armies of Hitlers….

So why do they say it? My sense is that their response reflects a general unease with the technology and ideas they don’t fully understand combined with a lack of vocabulary to articulate how they’re feeling. So Spider Goats make them feel very uncomfortable because it’s just so weird – but how do you decide whether it’s actually good or bad?

The only way round this is to go for specifics and make them use the information. Getting them to compare and contrast some of the applications of Genetic Engineering helps them see that, maybe, perhaps, it’s worth looking at the individual cases. Genetic Modification might well be “playing God” if you want to use that kind of vocabulary, but wouldn’t a compassionate God approve of Golden Rice and the chance to prevent millions of children going blind? Wouldn’t that, possibly, be an ethically Good Thing, despite it’s obvious un-naturalness and human hi-jacking of the so-called prerogatives of the Almighty…. Contrast Golden Rice with GM maize resistant to Round-Up, and think up some ethical arguments against that particular application of the technology.

My favourite lesson, however, is one that was inspired by a lecture from the Head of the Human Fertility and Embryology Authority (HFEA). I’ve found it a hugely enjoyable and effective use of role play, as well as a spring board for fascinating discussion of biological ethics. The HFEA is the UK’s independent regulator overseeing the use of gametes and embryos in fertility treatment and research. In other words, if you want to make use of any technology involving either gametes and/or embryos, you have to get HFEA approval first. This makes sense. Given the limitless potential applications of this technology, any blanket decision, for or against, would make no sense at all. This is the strength of the lesson, as the students have to consider every case individually and quickly see that it’s much more interesting and complicated than the reaction, “it’s un-natural!” can ever convey.

The main lesson planning goes into thoughtful allocation of the roles. First, you need 4 students who play the part of the HFEA itself. You explain that they are the panel who ultimately decide whether to allow specific uses of the technology available. They need to discuss the merits of the cases brought to them, and that they must make a reasoned and humane decision on each one.

The rest of the class are then divided into groups playing a variety of roles. They take it in turns to present their cases to the HFEA panel –I give each couple a brief precis of their situation on a piece of paper (PGD and the HFEA role play blank) so that no-one knows in advance what’s coming. They not only have to explain their situation to the HFEA, they also have to get into role and argue their case as passionately and persuasively as possible. When they’ve finished, and the HFEA are deliberating, I ask the rest of the class what they think. We take a vote (yes or no) and then compare it with the decision reached by the panel. It’s really important to get them to explain their answers, to push them beyond the trite and meaningless.

So who are the couples? Well, this is the bit I really like, because these are all genuine examples brought to the HFEA, so not only can we compare the decisions of the class panel and the class audience, we can then check back and see what the real HFEA actually decided.

The first three couples have all heard about PGD (Pre-implantation Genetic Diagnosis) and all want the same thing, but for different reasons.

There’s a couple who want to use embryo selection to choose the sex of their next baby as they’ve got 4 boys and really want a girl.

There next couple have also had 4 boys and they also had a girl. But the girl died, aged 5, in a bonfire accident caused by two of the boys. They want to have another girl to replace the one they lost.

The third couple also want their next child to be a girl, but this time it’s because their first child was a boy suffering from Duchenne Muscular Dystrophy.

I like this progression because after the initial, outraged and unanimous rejection of the first case, they see how life can sometimes be a bit more complicated and that ethical decisions might not always be straightforward.

But what about the others?

The lesbian couple who want to fuse their eggs and have a child that is entirely their own….

The deaf couple who want to select an embryo for deafness so that their child can share this special disability that has brought them together….

The 60 year old woman who has 3 adult children from a previous marriage and has a new husband who has never had children. She can become pregnant with the correct hormonal treatment, and using a donor egg and her husband’s sperm….

The scientists who want to create hybrid human/animal embryos, using the eggs cells of rabbits and the nuclei from human cells….

The managers of a sperm bank who are concerned at the proposal to remove anonymity for sperm donors…..

The IVF children who want to find their biological fathers….

One particularly interesting thing that emerges is that the class decisions nearly always reflect the actual decision taken by the HFEA. I find that rather reassuring.

I think the students also find it reassuring that these decisions are given the weight and gravity of full legal consideration that they deserve – check out the HFEA website to see a full list of conditions yet to be decided. You could use it as a source for updating the role play list, or as a research homework. Or you could ask them to consider the Zain Hashmi case (Zain Hashmi and embryo selection; Info for Zain Hashmi article debate;Qs for Zain Hashmi article ).

But if you’ve never tried this kind of lesson, I’d really recommend it.