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How does the concentration of a carbohydrate affect the rate of respiration?

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HOW DOES THE CONCENTRATION OF A CARBOHYDRATE AFFECT THE RATE OF RESPIRATION? PLAN: Aim: The aim of this experiment is to find out which carbohydrate produces the most energy in respiration. For this I have to find out which carbohydrate is best. Prediction: Once the best carbohydrate is found, we can vary different factors to find out if the carbohydrate works best in different conditions. In this case I will change the concentration. From this I can predict that the higher the concentration, the carbohydrate will produce more energy. The greater the concentration of the carbohydrate the more carbon dioxide, water and energy will be released. My reason for this prediction is that yeast is a unicellular fungus, which feeds saprophytically and can respire both aerobically and anaerobically. In the experiment the yeast will be respiring anaerobically and breaking down the glucose stored in it as a waste product of this process it will also form CO2 and alcohol in the form of ethanol. This respiration process is called fermentation. The yeast breaks down the glucose using a series of enzymes. Hypothesis: Which carbohydrate is used up most by yeast? ...read more.


These days were then made up. This experiment was performed fairly the only factor that may have been unfair was the fact we missed two days readings, although when we made them up the results seem to be fair. This experiment was very safe as well nothing was out of place and everybody work sensibly. There isn't any reason why it shouldn't be safe for people watching. Once the sucrose solution has been added to the beakers the yeast will be added into the beakers. Once that has been completed and everything has been added you mass each beaker and record the results. It would be better to take the readings three times each so that you can average them out and so fairer results can be taken. Water should be added to the u-bend of the tube to stop other gasses getting into it. If this did happen then it would affect the mass. The conditions that will be kept the same are the temperature of the surroundings, and the amount of yeast that would be added. Also making sure that the yeast came from the same cause. ...read more.


Well the mass loss of the 20% concentration was less then the 1% concentration on the first and second day. This does seem strange because the 20% would have respired quicker than the 1%. This might have happened because of a few things. One may have been subject to more light or have been shaken more than another. This does increase the kinetic energy and so the molecules would be bumping into one another increasing the chance of entering the yeast cell. This experiment I feel has been carried out very well and so is very reliable. Maybe to have made sure we could have put the beakers into a heating bath to make sure the temperatures were the same. Although this might not have made any difference the results might have still shown the same outcome. To extend this further I could use different types of yeast, maybe the next better carbohydrate at respiration, this being maltose. As I said before using other concentration possibly going higher to find trends, 25% or 30% concentration. Different pH's could be tried out because different carbohydrates work at different optimums. To find out how much has been produced we can use a gas syringe, which would hopefully make it more reliable. Harry Bowman 11f Mr Robinson Biology coursework ...read more.

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