What is Anaerobic
Respiration?
•This is a kind of respiration which do not
require any oxygen.
•Only some of the organisms can perform
anaerobic respiration, eg. Certain bacteria and
fungi.
•In anaerobic respiration, glucose is only
partly broken down. Much less energy (ATP) is
produced when compare with the aerobic
respiration.
Glucose
Energy + Ethanol + Carbon
Dioxide
THIS IS THE WORD EQUATION!
This is the Chemical Equation!
C6H12O6
ATP + 2C2H5OH + 2CO2
D Alcoholic fermentation is theD
basis of wine making. However,
ethanol is toxic to yeast. We
conduct this experiment to
investigate the effect of
concentration of ethanol on
anaerobic respiration.
Since ethanol is toxic to yeast, as
the concentration of ethanol
solution increase, the yeast is
inhibited to carry our respiration,
so we estimated that the anaerobic
respiration rate of yeast will
decrease as the concentration of
ethanol solution increase.
• As yeast will carry out anaerobic
respiration in the absent of oxygen,
ethanol will be given out which is
poisonous to yeast and respiratory rate
of yeast is then slows down. This can be
shown by drops in the increase in air
pressure in each syringe as the volume
of the syringes are kept constant.
• As carbon dioxide is produced during
anaerobic respiration, air pressure
inside syringe is increased which can be
detected by the low pressure sensor.
• Syringe x 6
• Beakers x 6
• Short rubber
tubing x1
• Computer x 1
• Data logger and
low pressure
sensor x 1
• Electronic balance
x 1
•
•
•
•
2g Yeast
10 cm3 of glucose
Distilled water
10 cm3 of pure
ethanol
1. Set up the computer and get Science
Workshop ready
2. 6 syringes and 6 beakers are prepared,
and labelled 1,2 to 6
3. Weigh 0.25g of yeast in electronic balance
for each syringe
4. Mix X cm3 pure ethanol and Y cm3 distilled
water, 1.25cm3 glucose, 0.25g of yeast into
each beaker according to the table below
X cm3 of water and Y cm3 of ethanol
Syringe
1
2
3
4
5
6
% of ethanol
solution
0
1.5
3
6
12
15
X cm3 of water 18.75
18.45
18.15
17.55
16.35
15.75
Y cm3 of
ethanol
0
0.3
0.6
1.2
2.4
3
Volume of
glucose
solution (cm3)
1.25
1.25
1.25
1.25
1.25
1.25
Total volume
(cm3)
20
20
20
20
20
20
• for example, in syringe 2
• total volume = 20 cm3, for 1.5% ethanol
solution, volume of ethanol added:
• 20 x 1.5% = 0.3 cm3
• volume of glucose solution added = 1.25cm3
• volume of water added = 20-1.25-0.3 =
18.45cm3
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 low 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 6 syringes
10. Take the slope of the graph of each syringe
11.The change in pressure / change in time =
slope = rate of anaerobic respiration
Setup for the Experiment
con. of ethanol rate of respiration
0
0.01856
1.5
0.01856
3
0.01642
6
0.01765
12
0.01453
Rate of anaerobic
respiration of yeast/kPa/s
Effect of concentration of ethanol solution on rate of anaerobic
respiration of yeast
0.02
0.015
0.01
0.005
0
0
5
10
15
Concentration of ethanol solution/ %
20
con. of ethanol rate of respiration
0
1.5
3
6
12
Rate of anaerobic
respiration of yeast/
kPa/s
Effect of concentration of ethanol solution on rate of
anaerobic respiration of yeast
0.025
0.02
0.015
0.01
0.005
0
0
5
10
15
Concentration of ethanol solution/%
20
0.01953
0.01652
0.01185
0.00795
0.00491
1. Some gas containing oxygen has entered the syringes,
and yeast may perform aerobic respiration.
2. Leakage of gas may occur, the pressure is not accurate.
R We can apply vaseline to the both connect tube and
any junction
3. The concentration of ethanol solution is not exact
because measuring cylinder is used.
R We can use the burette instead of the measuring
cylinder.
4. Temperature fluctuates.
R We can wrap the syringe with some cotton wool or put
in water bath, in order to maintain a constant
temperature throughout the experiment.
I
I
I
I
I
From the graph, we can see that the slope
is negative which means that as the
concentration of ethanol increase, the rate
of respiration of the yeast decrease
gradually. The increase in concentration of
ethanol inhibit the yeast to perform
respiration since it is poisonous to yeast.
H
By : Herby Cheung (5)
Margaret Ng (19)
Karen Wong (24) 6AS
Celene Ho (13) 6B
H