Enzymes and Immigration

I love using role play in Biology lessons to help illustrate or clarify biological processes. The Osmosis paper fight that I mentioned last week is one example. Role play works, I think, because as well as being fun and a bit different, it provides a vivid way of visualising something that’s working on an invisible, molecular scale. I always urge my students to try and “see” what’s going on in the test tube, and good role play can do this at least as well as a good animation.

Here’s an idea for helping clarify enzyme kinetics with your Year 12s. This one gets rave reviews – indeed, one student now studying medicine at Bristol said she still uses it in exams to help her answer questions. Goes something like this…

Bring all the students over to one side of the lab.

So, any of you ever been abroad?

Everyone’s hands go up.

When you went abroad, how many of you went in an aeroplane?

Again, it’s unanimous.

So, when your aeroplane landed in this abroad place, what happened next?

They run through the various rituals from baggage collection to passport control.

Right, let’s focus on passport control. I ask slightly less than half of the class (so 5 students from a class of 12) to come and sit on the 5 chairs I’ve arranged in a row along the side of the lab. I send the rest of the students over to the other side of the lab.

Right, I say to the 5 seated students, you lot are Immigration Officials. You’ve been given some Key Performance Indicators which include how quickly you can clear passengers as they come off an aeroplane. You’re super keen and you’ve all arrived early for work this morning!

But, I say to the rest of them, you passengers, after your 12 hour flight to Mongolia (or wherever), are feeling a bit frustrated because your plane has been put in a holding pattern above the airport while they wait for the pollution to clear.

Back to the seated students. So, what’s your rate of passenger clearance? How many passengers are you processing per unit time?



There aren’t any passengers!

Right! So how could we increase your rate of passenger clearance?

Give us some passengers!

OK! Back to the plane. Good news! Your plane has finally landed and you’re starting to disembark. Some of you are still struggling with the overhead lockers, but one of you has sprinted clear with your carry on bag and have got to Immigration!

Ask them to go and stand in front of an available immigration officer.

What’s happened to your rate of passenger clearance?

It’s gone up.

Can it go any higher?



More passengers!

And so I bring the rest of the flight through one by one, making sure they stay opposite their immigration officer.

When all the immigration officers are busy, I ask, can the rate of passenger clearance go any higher?

They can all immediately see it – No!

Why not?

They’re/We’re all busy!

So, turning to the passengers remaining, what do you have to do?

Wait for an immigration officer to become available.


Now reverse it! Send the 5 immigration officers to one side and have all the passengers landed and waiting at passport control…. Facing 5 empty seats!

What’s the rate of passenger clearance?


But why? There’s loads of passengers!

But there’s no immigration officers!

So how do we increase the rate?

Add an immigration officer!

I ask one of the 5 to take a seat and a passenger to be processed.

Can I increase it any more?



Add another immigration officer!

Keep going. Every time you add an officer, the rate goes up.

Wrap it all up by asking them to go back to their seats, and use the analogy to identify two factors that affect the rate of enzyme action, and sketch two separate graphs predicting the shape of the curve when these factors are plotted against rate.

They see the analogy immediately. It really helps them explain key ideas about available active sites and so on. They argue back and forth about the graphs, especially enzyme concentration (they quickly work out that substrate concentration must level off). This powerpoint animation might be useful at this point. enzyme and substrate conc animation Notice how it gets them to count the active sites vs substrate molecules.

The Casein/Trypsin practical is also a good follow up activity, partly because it illustrates the trend so nicely, but also for practising evaluation. Enzyme Concentration casein 2015

Next week is half term so will be Burble-less. Normal service will be resumed during the week of Mocks which follows.

Have a good fortnight!



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