Investigate the Factors That Affect the Rate of Respiration in Yeast

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Mashrek International School

Investigate the Factors that Affect the Rate of Respiration in Yeast. (Temperature)

Fawzi El Ansari

Biology HL

Title: Investigate the Factors that Affect the Rate of Respiration in Yeast. (Temperature)

Aim: The aim of this experiment is to investigate the effect of changing the temperature on the rate of respiration in yeast. This will be done by placing equal amounts of yeast in each beaker that contains the same pH solution. Each beaker will be mixed with glucose solution and then will be placed at a different temperature in which the amount of CO2 produced will be measured every one minute.

Rationale: As we all know, respiration is a process that takes place in all living organisms where it converts sugar, taken in by the organism into energy. Its formula is C6H12O6+ 6O2----> 6CO2+ 6H2O + ATP. The yeast in this experiment will have to respire an-aerobically because there will be an absence of oxygen. The higher the temperature the more kinetic energy there is. When there is more kinetic energy, the molecules will move faster thus colliding with each other more often, so therefore there will be a higher percentage chance of an enzyme colliding with its substrate successfully. However, once optimum temperature is reached, the substrate can no longer bind to the active site, and the reaction will no longer take place. Here, the enzyme will begin to deform and the hydrogen bonds formed between amino acids will break, and the yeast enzyme will begin to denature.

Hypothesis: If the temperature increases, then the rate of the reaction will increase and the rate of CO2 will increase until it reaches its maximum temperature and then begins to denature.


Independent Variable: Temperature of yeast solution
Dependent Variable: Rate at which CO2 is released by time
Controls: pH of solution kept at 7
Type of concentration of glucose sugar used
Time set of experiment for all trials is 10 minutes
Mass of yeast set at 4 grams.
Mass of glucose set at 10 grams

1) Yeast
2) Glucose sugar
3) Stop Watch
4) Test Tubes
5) Thermometer
6) Beakers 250mL
7) Electric Water Bath
8) Distilled Water 100 mL
9) Glass Rod
10) Digital Balance
11) Measuring Cylinder 15mL

1) Set the apparatus as shown in the diagram
2) Set the electric water bath to a temperature of 35 degrees Celsius 3) Place 10 grams of glucose powder into a beaker and add 100 mL of water. Swirl gently to mix. 4) Pour 20 cc of glucose solution into a clonical flask and add 4 grams of yeast to it. 5) Replace the bung in the flask ensuring an air tight seal. Fill the graduated tube with water and invert carefully into the beaker of water. Do not place over the end of the delivery tube. 6) Immediately position the graduated tube over the end of the delivery tube and measure the volume of CO2 collected every 1 minute for 10 minutes. 7) Repeat the experiment using different temperatures of water, 40 C, 50 C, and 60C. 8) This is how the variables were calculated:

1) The independent variable (the temperature of yeast solution) was changed every time by setting different temperatures on the electric water bath. 2) The rate of CO2 was measured by calculating the amount released from the graduated tube every one minute for ten minutes with the graduated tube being attached to the yeast and glucose solution. 3) The pH of the solution was kept at 7.

4) The same type of glucose sugar powder was used for all trials. 5) The time set for all the experiments was ten minutes and was calculated using a stopwatch. 6) The mass of the yeast was measured at 4 grams for each trial using a digital balance for each trial. 7) The mass of glucose powder was measured at 10 grams using a digital balance for each. trial Calculate the rate of CO2 released from each trial and present your data.

Safety Measures:...
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