Yeast growth

Yeast growth : How to study a fungus cell?

I- microscope observation

  1. Place a drop of the yeast culture you have in your beaker, on a microscope slide (you might have to dilute it a bit if you want to isolate a cell during your observation ).
  2. Place a coverslip on top and observe under different magnifications. High magnifications will be needed to see the yeast correctly.
  3. Draw a yeast cell and label it only with : membrane , nucleus, cytoplasm, if it is possible,the vacuole (that’s all you can observe with the optic microscope). Help yourself with the diagram of a yeast cell just below…

Diagram of a yeast cell labelled

by pinterest

A microscope observation (by motic microscope)

At home, you can visit this website to familiarize yourself with the cell structure : http://www.biocourseware.com/iphone/cell/index_pad.htm

II- HOW DOES SUGAR AFFECT THE GROWTH OF YEAST?

MATERIALS

  • 2 glass measuring cups, 2 beakers and 1 erlenmeyer flask
  • teaspoon
  • granulated sugar (saccharose)
  • distilled water
  • a packet of Yeast
  • scales
  • a microscope
  • Kova slides

A Kova slide is a special slide with 10 compartments called cupules to count cells.

notch = entaille

Each cupule has a grid with 9 large squares. Each large square is cut into 9 small squares. The volume of the entire grid (of the 9 large squares) is 1 µL. For a large square (formed of 9 small squares) is 0,1 µL. The volume of a small square is 0,01 µL.

protocole

  • You have a yeast’s solution (erlenmeyer 1 = yeasts with a high concentration of glucose or erlenmeyer 2 = yeasts with a low concentration of glucose).
  • Mix it and withdraw 10 µL with the pipette.
  • Put it in one cupule of the Kova slide : 1 µL is in the grid.
  • Use a microscope to count the quantity of yeast, first in a small square, then in a large square and finally in the grid.

1) How many yeasts do you have in your small square / large square / grid ?

2) How many yeasts do you have in your erlenmeyer / beaker ?

3) Fill in the table with your group’s results.

4) Calculate the average of the number of yeasts.

5) Compare the results of erlenmeyer 1 and erlenmeyer 2.

6) What do yeasts need to grow ?

Graph: (if we have time)

Prepare a graph to summarize the data you recorded in your table framacalc.

  • Label the Y-axis
  • then the X-axis time (days)
  • Choose an appropriate scale
  • Plot the data for yeast with no sugar and with sugar

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