3_respiration_is_yeast_alive


 * **Experiment - Is Yeast Alive?**

1. 2 test tubes, with live and boiled yeast respectively 2. add methylene blue and shake gently

Factors involved when leaving the test tubes to test for gas - Time - Temperature (warmth promotes the yeasts reactions) - Amount/Type of yeast (live or boiled)

Oxidation and Reduction of Methylene blue - becomes colourless when reduced (shake gently for reaction to occur)

LIVE YEAST SUSPENSION - reduced methylene blue foam observed - shows respiration of yeast BOILED YEAST SUSPENSION - blue dye remains the same

Conclusion: For oxidation/reduction to occur, live yeast is needed.

How does oxidation/reduction relate to electrons?

reduction of methylene blue - electron transfer from yeast cells therefore, the methylene blue must have entered/come in contact with the yeast cells **