BI100 Lab: Yeast Fermentation

This study sheet will be updated as the test/quiz approaches so be sure to check again!

__Objectives__:

- Demonstrate an ability to trap a column of yeast solution in a pipette, seal one end, and measure the resulting height of the carbon dioxide bubbles in the pipette over a period of 10 minutes.

- Demonstrate an ability to clearly graph the collected data.

- State the equations for aerobic respiration, muscle fermentation, and alcoholic fermentation, and contrast each of them with the other 2.

- Calculate the slope of the yeast fermentation line and state the meaning of this value

- Answer correctly, the questions provided at the end of the lab.

- pipette, yeast, sucrose solution, carbon dioxide, fermentation

- Fill in the blank questions - there will be around 5 fill-in-the-blanks from the “terms to consider”.

- Graphing - mock data will be provided so that students can construct a graph representing it. The graphs will be graded on their PRESENTATION of the data - there must be a title, labels, units, clearly plotted points, and a line drawn with a ruler.

- There will be a slope calculation required from the data graphed on the quiz.

- There will be 2-3 essays typed exactly from the essay questions in the lab manual.

- Given the Data Table Below and a sample piece of graph paper, be able to graph the data, list the coordinates to be used for slope, calculate the slope, and appropriately label ALL PARTS OF THE GRAPH (Title, Labels Units)!! BRING YOUR OWN RULER!! When you plot the points, put increments on the axis consistently The independent variable (minutes) is plotted on the x-axis (horizontal) while the mm CO
_{2}is the dependent variable and is plotted on the y-axis (vertical). When you write coordinates, the x value goes first, followed by the y value. Example: the coordinate of the first point of data is (3, 3.8). To calculate slope, circle two points, divide the difference in their y value by the difference in their x values. DO NOT REPORT THE SLOPE AS A FRACTION - DIVIDE IT OUT AND REPORT IT WITH UNITS (mmCO_{2}/min)!!

The slope of the line above is found by picking two points, such as the first and the third. The coordinate of the first is (3, 3.8) and the coordinate of the second is (9, 7.0). The slope is: (Y2-Y1)/(X2-X1), or (7-3.8)/(9-3) or 3.2/6; or 0.5 mm CO _{2}/minute.

BE SURE TO WRITE THE UNITS OF THE SLOPE ON YOUR TEST!! - Note that slope tells you the steepness of the line on the graph.

- Equations to know:
The chemical equation for aerobic respiration:

C_{6}H_{12}O_{6}+ 6 O_{2}---> 6 CO_{2}+ 6 H_{2}OThe chemical equation for yeast fermentation:

C_{6}H_{12}O_{6}---> 2 CO_{2}+ 2 alcohol moleculesThe chemical equation for human muscle anaerobic respiration (fermentation):

C_{6}H_{12}O_{6}---> 2 lactate moleculesReactants are to the left of the equation arrows above, and products are to the right of the equation arrows above. The equation arrow means “yields”.

- Cooling a yeast solution slows down the fermentation process, and slows down the carbon dioxide made per second.

- Another example: Use the following data to construct a graph and calculate the slope of the line:

- Graph the data:

**Minutes****mm CO**_{2}1 5 2 10 3 15 Calculate the slope of the line and explain what the value means:

Using coordinates (3,15) and (1,5): (5-15)/(1-3) = -10/-2 = 5 mm CO_{2}/ minute

The yeast are producing carbon dioxide at the rate of 5 mm per minute

- Graph the data:
- Note: The words “used/needed” mean the chemical is a reactant while the words “produced/made” mean the chemical is a product.