LS1.2 - Yeast Respiration

In this experiment you are going to investigate how either the concentration or the type of sugar impacts the rate of respiration in yeast. You will need your laptop and the Vernier data logging equipment to obtain data.

Yeast is a living organism and is commonly used in the production of bread and alcohol. Because yeast is alive, it respires the same as other living organisms. Yeast can undergo either anaerobic cellular respiration (fermentation) and aerobic cellular respiration. In this lab, oxygen is available to the yeast, so aerobic respiration will take place.

Yeast contains enzymes that aid in the process of respiration and just like in humans, these enzymes require a specific range in temperature to function. Therefore, this experiment must be carried out at temperatures between 34-40°C.

YeastYeast Also known as bakers’ yeast or Saccharomyces cerevisiae What is Yeast? Yeast is a single-celled living organism widely used in baking, brewing, winemaking and other industries. Saccharomyces cerevisiae can ferment and

Two Experiments Per Class

Concentration of Sucrose Solution (same sugar) (Groups 1-3)

Identify four sugar solutions:
1. 0% Sucrose
2. 5% Sucrose
3. 10% Sucrose
4. 15% Sucrose
Open Vernier Graphical Analysis
1. Download HERE
Labquest Setup:
1. Set collection RATE to 1 sample / second.
2. Set the data collection DURATION for 180 seconds.
3. You will not need to zero the sensor.
Obtain 4 test tubes
Add 3ml of 7% Yeast solution to each test tube.
Place them into a water bath of warm water (40°C).
1. Control the temperature by using a thermometer and adding cool water when needed.
In test tube #1, add 3ml of 0% Sucrose solution and let it incubate for 5 min.
At t = 5 min, add the gas pressure sensor and gently swirl the test tube.
Record the gas pressure for 180 seconds. Set in the LabQuest
Following the time table below, repeat this for each different type of sugar (5%, 10%, 15%).

Type of Sugar (same concentration) (Groups 4-7)

Identify four sugar solutions:
1. 5% Sucrose
2. 5% Glucose
3. 5% Fructose
4. 5% Lactose
Open Vernier Graphical Analysis
1. Download HERE
Labquest Setup:
1. Set collection RATE to 1 sample / second.
2. Set the data collection DURATION for 180 seconds.
3. You will not need to zero the sensor.
Obtain 4 test tubes
Add 3ml of 7% Yeast solution to each test tube.
Place them into a water bath of warm water (40°C).
1. Control the temperature by using a thermometer and adding cool water when needed.
In test tube #1, add 3ml of 5% Sucrose solution and let it incubate for 5 min.
At t = 5 min, add the gas pressure sensor and gently swirl the test tube.
Record the gas pressure for 180 seconds. Set in the LabQuest
Following the time table below, repeat this for each different type of sugar (glucose, fructose, lactose).

Visual time table of data collection:

Graph Menu

All of the following takes place in the 40˚C water bath.

At t = 0 min,
1. All 4 test tubes should be placed in the water bath.
At t = 5 min,
1. Add 3 ml of sugar sol #1 to test tube #1.
At t = 10 min,
1. Add 3 ml of sugar sol #2 to test tube #2. AND
2. Begin data collection on test tube #1.
At t = 15 min,
1. Add 3 ml of sugar sol #3 to test tube #3. AND
2. Begin data collection on test tube #2.
At t = 20 min,
1. Add 3 ml of sugar sol #4 to test tube #4. AND
2. Begin data collection on test tube #3.
At t = 25 min,
1. Begin data collection on test tube #4.

Why does the pressure increase?

Of these variables, in the experiment we held the Temperature (T), Gas Constant (R) and the Volume (V) constant. Therefore the increase in pressure (P) must have been from additional molecules of gas (n). These molecules were released by the yeast through the process of cellular respiration.

The Ideal Gas Law describes the relationship amongst four variables of a closed container of gas (your test tube). From the equation:

P - Pressure - Amount of force per square meter [N/m² ] or [Pa]. This is a measurement of the force the molecules of air are exerting on the walls of the container. 1 kPa = 1000 Pa.
n - Number of molecules present.
R - Gas Constant - This value converts the measurements of the other variables into the mks system of measurement (numeric values that we can use)
T - Temperature of the gas, measured in degrees Kelvin [K]. 0 K = -273.15 ˚C
V - Volume of the gas/ container. Measured in m³

Collecting Data from the Graph.

Once your data collection has been completed, you will determine the slope of each trial /run.
1. Select / highlight a linear portion of your data.
2. Using the graph button in the lower left corner, select Apply Curve Fit. (See image above)
3. Select Linear fit.
4. Record the value of the slope (m value) (Gas Production Rate) in the appropriate place in the class data table.

Class results and Questions

Questions to Consider:

Concept: List the inputs and outputs of a yeast cell when it undergoes cellular respiration.
Data Analysis: From the data, create a claim regarding the effect of the concentration of sucrose and the rate of gas produced.
1. Provide at least 2 pieces of evidence that supports your claim.
Lab Evaluation: Name two control variables for the experiment.
Lab Evaluation: Evaluate the experiment to determine how we (as a class could have collected better data).
Data Interpretation: Explain the significance of the x-intercept in the graph.
Data Extrapolation: Suppose a 25% solution of Sucrose was used in the lab. Predict the rate of gas production [kPa/s]

Questions to Consider:

7. Data Analysis: From the data, make a claim regarding the type of sugar and ability of yeast to process the sugar.

1. 1. Provide at least two pieces of evidence to support your claim.

8. Lab Evaluation: Name two control variables for the experiment.

9. Lab Evaluation: Evaluate the experiment to determine how we (as a class could have collected better data).

10. Data Analysis: Using the graph, which substrate was the best for the yeast in terms of releasing energy quickly? Explain your answer. [3 marks]

11. Application: Specific organisms need specific diets. Comment on the best type of diet for a yeast cell.