Science – Yeast Experiment: measuring respiration in yeast – Think like a scientist (8/10)

In this experiment we’re going to look at life in action and investigate some of the ingredients that make life work. Now most organisms need air to breathe and some kind of energy source
to live. And by energy, we usually mean food. But in order to thrive and multiply, conditions need to be just right. And that’s what we’re going to investigate. We’re going to use a very simple form of life. This is baker’s yeast, and it’s alive. It’s a tiny single celled kind of a fungus. And given food and air, it will grow and multiply. But we’re going to see which kind of conditions it likes best. And to do that, I’m going to make up a series of sugar solutions. Before you start, print off the glass diagram from your study journal so that you can record which sugar solution is which. I’ve got four glasses each with a spoonful
of sugar in, and I’m going to add the same amount of water to each. So this first one, I’m going to add cold water. In the next one, I’m going to put in the same amount of just boiled water from the kettle, but be careful you don’t crack the glass. In the final two, I’m going to put the same amount of water that’s
at body temperature or blood temperature. So I’ve just tested that with my finger. Now give them a quick stir. Cold water. Boiling water. Blood warm, and blood warm. So now I’m going to add a sachet of yeast to each glass. Then I’m going to mark off the level of the water on the side of the glass. Now this last glass, I’m going to cover with cling film to restrict the amount of air that the yeast has to work with. Set your experiment up in the same way, so we can compare results. I’m going to give this five minutes and see if anything’s happened. Well that’s five minutes up and the yeast is clearly sprung into action because it started to produce a foam. This foam is the result of the yeast using the oxygen in the air to digest the sugar. It’s producing a gas as a waste or byproduct. In this particular case, it’s carbon dioxide.
And that’s the process that makes bread rise in the same way as its doming and making the cling film rise here. Now to monitor the experiment – and keep track of the process – I’m going to measure the thickness of the foam and record how it changes over time. So this one is 2 centimetres thick after five minutes. And this one is 2 centimetres thick. I’ll give that another five minutes, and then I’ll come back and make another measurement. Well that’s 10 minutes up, and this one – which was the boiling water – doesn’t seem to be doing very much at all. This one – which was the cold water – appears to be just starting to produce a very thin layer of foam. And these two are still doing really well, and producing more
foam. I’m just going to measure the thickness again. This foam has gone up to 6 centimetres. And this one is 5 centimetres. Now to find out what these observations mean and to interpret the results, you’ll need to join in with the online discussion. Get more from the Open University Check out the links on screen now.

Comments 31

  • where do i go to get involve in this online discussion to interpret the results?

  • It's still surprise me just how many people
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  • She got a lot of make up on

  • what temperature was the cold water???
    I need it for my thesis… 😛
    plus how much of water was used exactly?…

  • by adding water you are decreasing air and you make it an incomplete study. you need to test for both factors.

  • this was no help ok you need to find a better dayjob

  • 👍👍👍

  • amazing video👍👍👍

  • Smoking hot

  • she sounds like Siri on iPhone

  • What was the problem ?

  • I want to die

  • Now I understand why my yeast always die… 😅
    Thanks alot for sharing this video!

  • id tap that

  • Of course the yeast in the boiled water shows nothing because the bacteria was completely killed like you use a dishwasher to get rid of bacteria and dirt on your dishes. Totally unnecessary attempt… 🤦

  • could you please help me to understand the role of potassium in increasing CO2 amount produced by yeast? appreciate your help.

  • I likes to see this type of practical

  • Amazing Vid!

  • I did this an experiment with just a single grain of yeast to see if it can divide with body temperature water

  • can we appreciate the fact that this experiment was scripted?

  • why did she cover the test tube with glad wrap? and not all of them???

  • 1:08 FôŪr GłÁsšĒs

  • Ive seen this video a solid 40 times in my science class smh

  • @GenaropizzaGuy. U said Cold water mamon. U lyinq to us?

  • ah yes i already forgot about the scientific finger dipping method. super accurate stuff

  • The first glass which contains cold water has a relatively lower temperature than the other three glasses of solution. With this, the sugar molecules and enzymes possess less kinetic energy and the chance for effective collisions(the sugar binding with the active site of enzymes) is also lower.Therefore, enzymes which are required in aerobic respiration of yeast in glass 1 energy work inefficiently. With less sugar being oxidized, less energy is released for cell division or other metabolic activities per unit time. Therefore, they grow at a slower rate.

    The second glass of solution actually contains boiling water with its temperature near 100 degrees Celsius. The fact that the yeast does not show obvious growth is due to the denaturing of the enzymes(the changes of the shape of active site, resulting in the active site being not able to bind with sugar to form enzyme-substrate complex). Besides yeast may be killed under such a high temperature. Ultimately, no obvious growth is observed.

    The third glass of solution is at body temperature(~36 degrees Celsius), which favors the enzymatic reaction(aerobic respiration of yeast). As this temperature is near the optimal temperature, the enzymes can work efficiently, food is oxidized and energy is released at a more rapid rate. Cell division is favored with more energy released. Therefore, the yeast in this glass shows the fastest rate of growth.

    In the last glass of solution(If I haven't missed any information), the cup is covered with a plastic wrap. The type of respiration carried out by the yeast is mainly anaerobic respiration, in which sugar is oxidized less completely and as such less energy is released. Owing to this, yeast in glass 4 grows slower than that in glass 3 even both glasses of solution are at the same temperature.

    I hope my answer will be of help. Are these the principles of the experiment? If there are any mistakes, I am looking forward to your advice.

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