+

Anaerobic respiration

Fermentation

+Scientific Concept

Anaerobic respiration occurs in conditions of limited oxygen supply or in the absence of oxygen.

During anaerobic respiration, the glucose os not fully oxidised to carbon dioxide and water but partly disintegrates into ethanol and carbon dioxide in plant cells.

C6H12O6 2C2H5OH + 2CO2 + 2ATP

+Engage

+

Question?

What are the important

ingredients do you need to make a

bun?

What makes the dough

expand and becomes bigger?

How to control the bun expand

and becomes bigger in the

shortest time?

+Empower

+

4 grams of yeast was measured by the electronic balance.

Glucose solution was prepared in a beaker. Different concentration of glucose solution was prepared as follows :

5%, 10% and 15%

The glucose solution of 5% was boiled under the Bunsen flame to evaporate any dissolve oxygen in the solution

This glucose solution was cooled down by the ice to prevent the heat produced killed the yeast during the fermentation.

The carbon dioxide sensor was connected with the Data Logger.

+ Glucose solution was then mixed with the yeast in the reagent bottle under the water bath with temperature 30oC. Water bath was prepared to maintain the temperature as heat produced will affect the reaction during anaerobic respiration.

A layer of oil was added on the top of the solution to prevent gas trapped in the solution.

The carbon dioxide sensor healed the reagent bottle of the mixed solution.

The reagent bottle was put under the water bath for 10 minutes.

The amount of carbon dioxide was recorded at each 10 seconds interval.

Step 4 to 11 are repeated but the concentration of glucose solution is changed to 10% and 15% respectively.

+Result

From the graph and table, it is shown that the fermentation of 5% of glucose produced the highest amount of CO2 and the highest rate of fermentation. While fermentation of both 10% and 15% of glucose have produced almost same amount of CO2 in the same period of time, both also have steady rate of respiration.

Cencentration of glucose

Initial Final Rate of Respiratio

n (ppm/min)

5% 758.154 5960.923 212.73

10% 590.769 2924.308 122.45

15% 738.462 3042.462 96.72

+Question

Look at the table, why does the carbon dioxide level change?

Base on the graph, which fermentation of glucose produced higher amount of carbon dioxide gas? Why?

Calculate the rates of respiration of each concentration glucose by using the formula given below.

Rate of respiration = Final reading – initial reading

Time (min)

+Answer

The change of carbon dioxide level indicated that the yeast fermentation of glucose have begun. Or anaerobic respiration has initiated by yeast.

In the same period of time, fermentation of yeast in glucose 5% have produced higher amount of carbon dioxide. This can be explain as in high concentration of glucose such as 10% and 15%, the increase in glucose concentration led to in the increase in fermentation time. Besides, when the glucose content increased, the glucose uptake rate decreased, this will affect the rate of fermentation. Thus, as longer time is required for fermentation of yeast to occur, it have reduced the amount of CO2 produced for both 10% and 15% of glucose fermentation.

+Discussion

The fermentation of glucose, which occurs primarily when the glucose concentration is high or when oxygen is not available.

The cells have a low energy yield of only about 2 ATP per mole of glucose metabolized. The stoichiometry of this reaction is

C6H12O6 2C2H5OH + 2CO2 + 2ATP

+ The influence of different glucose concentration on metabolic activities of yeast was evaluated by the overall amount of CO2 and rate of reaction.

In high concentration of glucose such as 10% and 15%, the increase in glucose concentration led in the increase in fermentation time.

Besides, when the glucose content increased, the glucose uptake rate decrease, this will affect the rate of fermentation.

Thus, as longer time is required for fermentation of yeast to occur, it have reduced the amount of co2 produced for both 10% and 15% of glucose fermentation.

Conversely, for the same reason which mentioned above, fermentation of 5% glucose have produced the higher amount of CO2 and with the highest rate of fermentation.

+Enhance

In the production of fruit wine, most fruits have natural sugar in them and without

adding extra sugar, these can be turned into a wine of about 4% to 6% volume alcohol.

This is a low alcohol content.

How high alcohol content of fruit wine is produced?

To make a stronger wine about 12% to 17%i sugar is needed to bring the alcohol content up to level high

enough.

The increase in glucose concentration led to in the increase in fermentation

time. Besides, when the glucose content increased, the glucose uptake rate decreased, this will affect the rate of fermentation whereby it will prolog the fermentation process, resulting in higher amount of by-product produces in time. Thus, producing fruit wine with

alcohol content.

+Unique Feature of this Activity

1. Amount of carbon dioxide produced can be detected and measured accurately. We can measured in every 10 seconds and the data can be recorded up to three decimal places.

2. Less work need to be done by the students. For example, students do not need to be with the experiment all the time as the result will be recorded automatically during that period of time.

3. The pattern of amount of CO2 production changes can be observe along with the experiment.

4. The changes of the data in table and graph can be observed immediately, allowing us to halt and repeat the experiment easily.