Protists such as paramecium engulf solid food, forming food vacuoles, within which the food is digested. The following figure illustrates this process:

What can you deduce from this Illustration?

As you can see, four different phenomena are observed simultaneously:
A. The food vacuole moves around the cell with time (as is evident by microscopic observations).
B. The pH within the food vacuole changes constantly (as is evident by the Congo red dye changes within the vacuole).
C. The yeast cells within the food vacuole are degraded (as is evident by microscopic observations).
D. The vacuole’s size changes (as is evident by microscopic observations).

During this tutorial you will try to determine the (simplified) mechanisms underlying these phenomena. You will perform various virtual experiments. Each experiment will be followed by several multiple-choice questions. The different answers will lead you to additional comments and explanations. Wrong answers can lead you to valuable comments and insights, so don’t rush through the tutorial.
Take your time and examine several possibilities during each step.

Our purpose is to demonstrate how do scientists approach such problems. All the virtual experiments discussed below were not performed by us, so we cannot guarantee that the mechanisms found here are the correct mechanisms underlying these phenomena.

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