Is+Yeast+Alive?+-experiment

IS YEAST ALIVE?
Why did the yeast foam when added to glucose? The yeast respired and produced carbon dioxide. As the glucose was heated, this increases the rate of respiration and cause carbon dioxide to be rapidly produced. Therefore, foaming was observed.

Rate of Respiration-> Amount of carbon dioxide-> measure height of froth __**Constant variables**__ - Time - Temperature

Methylene blue is an indicator to see if a chemical is reduced (colourless) or oxidised (coloured)

Live yeast: When blue methylene blue is added to the yeast, the methylene blue will be de-colourized. This shows that the methylene blue is reduced, gaining electrons
 * || Colour of solution at 0 min || Colour of solution at 5 min ||
 * A || light blue || become milky ||
 * B || dark blue || remain dark blue ||

Dead yeast: There is no oxidation or reduction when the blue methylene blue is added to the yeast. The suspension remain blue.

Methylene blue is a small molecule that is able to diffuse into all yeast cells. Live yeast cells will de-colourize methylene blue and thus appear colourless under the microscope. On the other hand, no reaction takes place within dead yeast cells and methylene blue remains blue.