1. Add 10cm^3 of 5% yeast suspension to three boiling tubes labelled A, B, C 2. Add 10cm^3 of 5% glucose solution to tube A, sucrose solution to tube B and maltose solution to tube C 3. Add three drops of Janus Green B indicator to each boiling tube and gently shake to mix the contents 4. Add a thin layer of liquid paraffin (2mm thick) to the top of each boiling tube 5. Leave the boiling tubes until the Janus Green B indicator has changed colour from blue to pink 6. Insert the bung in tube A and stand it in the water bath. The clip should be removed or open. Leave the tube to equilibriate for 5 minutes 7. Close the slip to seal the apparatus and mark the level of the meniscus 8. Use a ruler to mark another line 10mm higher than the miniscus 9. Start the stopclock and time how long it takes for the miniscus to move from its original positition to the 10mm line 10. Repeat 3 times 11. Work out rate of respiration of the different sugars by taking 1000 divided by the mean time for each sugar
The fluid moves due to the yeast producing CO2 in anaerobic respiration. This increases the pressure inside the apparatus pushing the red liquid along the tube. You can tune the movement of the fluid to give an indication of the rate of anaerobic respiration.
Hi, I had three questions after watching the video, I would be so pleased if you could answer them for me .Why is the tap open when the apparatus is assembled? and why is the tap not closed until after 5 minutes after setting up? Why are no readings taken before the indicator changes to pink
Hi! Is it possible for the sucrose to produce more co2 and have a faster rate given that it needs to be brokendown first into glucose by the enzyme coming from yeast? rather than the readily glucose?
Where did you order the capillary u tubing from?? Im planning on doing this experiment for my ib Bio class, but I can't find the tubing anywhere... Thanks
Rebecca Olson you can buy the straight capillary tubing and bend it yourself. Flint glass is easier to bend as opposed to borosilicate glass (Pyrex) which is more difficult to work with. A good technician may know how to do it or you can find info and demonstrations on the internet.
Excellent video, really helpful and well explained. Quick Question, instead of measuring how long it takes for the fluid to move up a set length of the tube (in this case 1 centimetre), would it also be possible to measure the length moved by the fluid in a set length of time?
Zylo gamer yes you could do that. Both ways will allow you to calculate a rate and it does work in aerobic conditions but not as fast. Bung and tube from any scientific school supplier.
Hi! i love your channel it has helped me a lot. What I want to know is which practicals do I have to perform if I am giving my AS and A2 together. It will be of great help if you can list me the practicals......... no one is helping me out I have tried reaching out to people and I am doing this all alone at home without coaching or any help because I can't afford it and I really need this.
Mona Bey The 12 practicals in my channel are the 12 required by AQA exam board For A2 Biology. Learn them all. Good luck. Doing AS and A2 biol on your own at home is tough.
yeah... tell me about it but i am in zone 4 and i am from pakistan so some experiments arent usually performed here because they are too sophisticated.
Is it possible to do an experiment similar to this but in aerobic conditions? And what did you put in with the yeast to get that brown solution? we will be given 15g only to work with
The yeast is that colour naturally. It is simply a suspension of yeast in warm water with a little glucose added. Yes it would work in aerobic conditions.
+Biology Practical Activities and Revision Thank you for your fast reply! To do it in aerobic conditions I do the experiment without adding the oil correct? and I'm not sure our school will provide us with janus so I doubt I will use that either
Can you tell me what was the red liquid used in the capillary tube? By the way, is there anywhere an access to all of the results received in your experiment? They would be really helpful, serving as comparative values for my own results. Thanks in advance.
Mateusz Kowalski you can use any red liquid. Ink and food colouring are good. I’ll work in getting the results on here. I thought they were on the end of the clip bug maybe not all of them.
Okay, by the way, was the experimental set-up picture taken from the Internet or you made it by yourself? If it was self-made, could you give me an access to it? I would appreciate it.
Double Stuffed Ramen Oreo is the oil layer thick enough to stop oxygen. Are the yeast active and at a good temperature e.g. 40 and is it brewers yeast as opposed to bakers yeast. Brewers works much better.
It should go pink in around 10 mins as long as the yeast is active at 40C with some glucose first. Also use brewers yeaat instead of bakers. It works much better.
Is it correct to say that paraffin ONLY prevents O2 diffusion, and not CO2 diffusion? CO2 technically is a bigger molecule, so why can it pass through paraffin while O2 cannot?
Zezemint it reduces not completely prevents gas diffusion. As CO2 is being produced at quite a high rate by the yeast, the very steep concentration gradient results in more CO2 escaping.
Kai it maintains a constant temperature so that in this case temperature doesn’t become a confounding variable. You could also vary the temperature of the water bath if you wanted to investigate the affects of temperature on respiration rate.
no no Well there isn’t really an hypothesis. But you could predict the best sugar or optimum temperature and put it to the test so the hypothesis could be: The monosaccharide glucose will produce a faster rate if anaerobic respiration in yeast than the disaccharides Maltose and Sucrose.
