The Effects of Concentration of Sugar on the Respiration Rate of Yeast

The Effects of Concentration of Sugar on the Respiration Rate of Yeast

Investigating the effect of concentration of sugar on the respiration

rate of yeast

We did an investigation to find how different concentrations of sugar

effect the respiration rate of yeast and which type of concentration

works best.

Respiration is not breathing in and out; it is the breakdown of

glucose to make energy using oxygen. Every living cell in every living

organism uses respiration to make energy all the time. Plants respire

(as well as photosynthesise) to release energy for growth, active

uptake, etc…. They can also respire anaerobically (without oxygen) to

produce ethanol and carbon dioxide as by-products. This reaction is

shown in the equation:

Glucose

Ethanol + Carbon Dioxide + Energy

C6H12O6

2C2H5OH + 2CO2

Anaerobic respiration by yeast is generally called fermentation. Yeast

is a living organism that produces enzymes. These enzymes break down

glucose (by colliding with each other) to be able to respire

anaerobically.

I predict that the rate of fermentation will increase proportionally

as the concentration of sugar increases but only up to a certain point

were it will begin to decrease and eventually stop.

I believe this because the more sugar added to the yeast the more

glucose broken down producing ethanol and carbon dioxide. The rate of

carbon dioxide produced in a minute will also increase because the

higher the concentration of sugar the more heat energy produced and so

the more the molecules will move around and collide. Also the higher

quantity of glucose molecules the higher chance of them colliding with

the enzymes.

I believe the reaction will slow down and eventually stop when the

sugar reaches a certain concentration because the yeast will be killed

by either:

1. The high concentration of ethanol produced as a by-product.

2. The temperature of the reaction, as some of the energy produced

converts into heat energy. At really high temperatures the reaction

will stop because the heat will have denatured the enzymes.