What is Anaerobic Respiration?

This is a kind of respiration which do not requireany oxygen. Only some of the organisms can performanaerobic respiration, e.g. Certain bacteria and

fungi. In anaerobic respiration, glucose is only partlybroken down. Much less energy is produced sincethere is no oxygen, so the reaction can not carry out completely by entering the electron system in order to produce more ATP.

Glucose Energy + Ethanol + Carbon Dioxide

THIS IS THE WORD EQUATION!

C6H12O6 ATP + CH3CH2OH + CO2

THIS IS THE CHEMICAL EQUATION!

• Alcoholic fermentation is the basis of brewing and wine making. But ethanol is toxic to yeast. We conduct this experiment to investigate the effect of concentration of ethanol on anaerobic respiration of yeast.

What is our aim to conduct the experiment??

•We estimated that the respiration rate will decrease with the increasing concentration of ethanol. •Since ethanol is poisonous , as the concentration of ethanol increase, the yeast will be inhibited to carry out respiration and hence the respiration rate of yeast will decrease gradually.•Some of the yeast may die because ethanol is toxic to yeast.

1.Set up the computer and get Science Workshop ready

2.5 syringes and beakers are prepared,and labelled

1,2,3,4 and 5

3.Mix pure ethanol and distilled water according to table below into a beaker

Percentage of ethanol

solution (%)

0 1.5 3 6 12 15

Volume of water (cm3) 18.75 18.45 18.15 17.55 16.35 15.75

Volume of ethanol (cm 3) 0 0.3 0.6 1.2 2.4 3

Volume of glucose (cm 3 ) 1.25 1.25 1.25 1.25 1.25 1.25

4.Weight 1.25g yeast cells was put into each

beaker and mix the suspension of yeast cells,

ethanol and water thoroughly

5.25 cm3 of the glucose solution is then introduced

into the syringes

6.The syringes are filled by the mixture in the beaker

through the nozzle by the plugger

7.A free end of rubber tubing is attached to the nozzle

of the syringe, another end is attached to the

pressure sensor connected to the data logger

8.Data is then recorded as a graph

9.Repeat the above steps in order to obtain result for

5 syringes

The Setup for the Experiment

1.Some gas may enter through the linkages and the yeast may perform aerobic respiration.

2.Leakage of gas may occur, the pressure is not accurate.

3.The concentration of ethanol solution is not exact because measuring cylinder is used.

4.The pressure change is very small, the pressure sensor may be very sensitive .

The effect of change in concentration of ethanol solution onanaerobic respiration of yeast

0

0.005

0.010.015

0.02

0.025

0 5 10 15 20

Concentration of ethanol solution/%

Cha

nge

in p

ress

ure/

kPa

0 0.019531.5 0.01652

3 0.011856 0.00795

12 0.0049115 0.00476

By: Herby Cheung (5)

Margaret Ng (19)

Karen Wong (24) 6AS

Celene Ho (13) 6B