there is another experiment that you have to know pertaining to respiration and that is measuring the rate of respiration in yeast so as an example imagine if you were just looking at a test tube and inside the test tube it contains yeast and glucose solution so if you were to magnify it you are able to see the yeast which are just unicellular fungi but the problem is if you're looking at the test tube the question is are the yeast respiring can you actually see the yeast respiring you can't because number one they're too small and number two even if they are carrying out respiration and they produce carbon dioxide you know um you we can't see the carbon dioxide being produced or we can't see the oxygen being used up you may be able to use the previous experiment to measure the rate of respiration remember the one where we use the soda lime and we see the movement of the colored droplets but there is actually an easier way when we are measuring the rate of respiration in yeast so normally in the yeast cytoplasm what happens is we are just focusing on one part of the uh one chemical reaction where glycolisis takes place and in glycolysis the glucose is broken down into pyrovate as usual it requires to ATP and it produces for ATP we've seen this in glycolysis but also what happen happens is oxidation takes place oxidation means when the glucose is broken down hydrogen atoms are released and what happens to the hydrogen atom by the way the hydrogen atom will be accepted by hydrogen carriers which are nads and when the NAD accepts the hydrogen atoms they become reduced NAD so in the East cytoplasm when glycolysis takes place we still don't know that this reaction is happening because we cannot see the glycolysis taking place in this situation and in glycolysis it also involves two very important processes it involves oxidation where hydrogen atoms are removed and it also involves reduction where the nads receive the hydrogen and they are getting reduced like I said we cannot see this with our eyes so the question here is is there a particular way for us to see it happening particularly the oxidation and reduction part the answer is actually yes we can use something called a Redux indicator the word Redux is just a shortened form of reduction and oxidation so a Redux indicator can be two things which are either a solution known as dcpip D chlorophenol indenol you don't have to remember the long name dcpip is good enough or methylin blue so what exactly do this reduxx indicator do well the first thing we do is we will actually add the dcpip or methylin blue not both at the same time but just one or the other I'm just focusing on dcpip by the way so let's say we add dcpip to the yeast and glucose solution what happens is the entire thing becomes blue in color because that is the original color of DCP IP so as you can see the yeast are all immersed in the DCP IP and the good news over here is dcpip or methylin blue are not toxic to the yeast that is important to know because sometimes in the exam they may ask you the question why is it that we use dcpip in this experiment then you have to explain that ah we use dcpip because it is not toxic but what exactly is the dcpip used for over here so let's talk about that part you see under normal circumstances when the glycolysis happens in the cell it will release hydrogen atoms which is oxidation and the hydrogen atoms will be accepted by the nads to become reduced but the hydrogen has two choices either it gets accepted by the nads to become reduced nads and that's where reduction takes place but here's the thing when NAD gets reduced and becomes reduce n there is no difference we it is not visible to our eyes but the beautiful thing here is the dcpip can also act as an artificial hydrogen acceptor so when the dcpip accepts hydrogen the dcpip becomes reduced dcpip and here's where it's important dcpip by itself is blue in color but reduced dcpip is colorless and this is visible in our eyes because as dcpip becomes reduced the color in the solution the blue color in the test tube will gradually become colorless and that is visible in our eyes so the reason why we use dcpip or methylin blue is it can accept the hydrogen and be reduced into a colorless compound so we can see the Redux reaction taking place so we know that as the dcpip becomes colorless the glycolysis or the respiration is taking place in the yeast it is just a way for us to prove that oh the yeast is undergoing respiration that's why we use the dcpip or methylin blue as a Redux indicator so for example if you are still not familiar with this let's look at it again I've prepared two test tubes with the same volume of yeast and glucose and for both these test tubes I've added dcpip solution or methylin blue up to you and as you can see both the solutions are blue in color because of the dcpip the difference here is one test tube is put into a 10° C water bath and the bottom test tube is put in a 20 ° C water bath so we want to see the effect of temperature on the respiration now obviously the yeast at 10° C will have a lower respiration rate and the yeast at 20° C will have a higher respiration rate why is that so because temperature affects enzyme activity and 10° C uh will cause the enzymes and substrates to move slower therefore lower rate of reaction and 20° C higher kinetic energy of enzymes and substrates and they will carry out faster respiration but how do we prove it so remember just a bit of revision the glucose during glycolysis we are just focusing on glycolysis here glucose when it under goes glycolysis it produces two pyro and the hydrogen atoms are released through oxidation and normally we can use dcpip to accept the hydrogen and when dcpip accepts hydrogen it becomes reduced dcpip where the blue color will become colorless so with this we know for the fact that for the yeast at 10° C the reaction will be slower where the dcpip becomes reduced dcpip much slower but because the yeast at 20° C has a higher respiration rate that entire reaction will happen much faster so how do we prove it we measure at the start of the experiment we have a stopwatch and we measure the time taken for the DC cpip to decolorize so for example don't memorize the results the yeast at 10° C took 150 seconds to decolorize the dcpip but the yeast at 20° C only took 40 seconds so the dcpip gets decolorized much faster because it was being reduced much faster why because more hydrogen atom was released due to a higher respiration rate it's as simple as that so by this we can actually prove that the yeast at 20° C will have a higher respiration rate or faster respiration rate than the yeast at 10° Celsius that's the application of using the Redux indicator such as methylin blue or dcpip and it's the same for methylin Blue by the way when methylin blue accepts the hydrogen atoms it becomes reduced methylin blue where the blue color becomes colorless as well so you can either use dcpip or methylin blue in the exam that's entirely fine