Yeast

When glucose reacts with yeast, carbon dioxide is given off by the yeast ~ hence, froth is produced To speed up the reaction, the glucose can be warmed. Yeast is quite tolerant to heat.

If required to measure the height of the froth to determine amount of carbon dioxide, certain variables must be kept constant: -time -temperature -amount of water/glucose -amount of yeast

Oxidation ~ losing electrons, not presence of oxygen Reduction-gaining electrons

Methylene blue is an indicator to see if the chemical is reduced or oxidised. No reaction (neither oxidation nor reduction) takes place in the boiled(dead) yeast - turns out blue However, reactions take place in the live yeast - turns out colourless

Under the microscope: Methylene blue diffuses through all yeast cell membranes. If the yeast cell is alive, that means that reactions are taking place and therefore it will turn colourless. Those that remain dark blue are dead.