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relationship between glucose concentration and the rate of yeast respiration

Experiment on what is the relationship between glucose concentration and the rate of yeast respiration.

1. Research question: How does glucose concentration affect the rate of yeast respiration?

2. Hypothesis:

- Respiration of yeast is a step that yeast breaks down the glucose to make energy using oxygen [1].

- I predict the rate of yeast respiration (amount of CO2 produced) will increase as the glucose concentration (amount of sugar) increases.

- I predict this because the more sugar added to the yeast mixture (yeast and water), the more glucose will be broken down by yeast [1] and that produces carbon dioxide which stands for the sign of yeast respiration.

3. Introduction:

Yeast respiration is a very important step in food production because it can be used in producing alcoholic beverages such as beer, wine and liquor. It can be used in the bread making business in which yeast respiration can help to increase the volume of the bread, bring about higher taste quality for the products [2].

In this experiment we will examine about the relationship between glucose concentration and yeast respiration rate. To achieve this objective, all variables are kept constant whereas the glucose concentration is increased gradually. The rate of respiration is measured accordingly. In this manner, the relationship between glucose concentration and yeast respiration rate can be determined.

4. Method and Materials:

4.1. Variables:

4.1.1. Independent variable:

The amount of sugar in the yeast and water solution

- 2g

- 4g

- 6g

4.1.2. Dependent variable:

The amount of carbon dioxide gas will be produced

4.1.3. Control variables:

- The amount of time

- The temperature

- The volume of yeast

- The amount of water

- Same type of measuring cylinder

- Same type of sugar

4.2. Materials & Equipments:

Yeast (3g  x 3 tests = 9g)

Sugar (12 g x 3 tests = 36 g)

Water (90ml x 3 trials = 270ml )

Funnel (x3)

Measuring cylinder (100ml type)




5. Results:

Table 1: Relationship between glucose content and rate of respiration

                  Glucose                     content



2g  (6.7%)

4g  (13.3%)

6g  (20%)


















Graph 1: Relationship between glucose content and rate of respiration

6. Discussion and conclusion:

After the experiment, it can be seen that when the glucose concentration increases, the rate of respiration decreases. It could be because of the osmotic pressure. When the level of glucose increases, there is higher level of osmotic pressure and slows down the metabolism of the yeast therefore decreases the rate of respiration [2]. This is opposite from the hypothesis that I have at the beginning because I thought that the higher the glucose concentration, the higher the rate of the yeast respiration.

Regarding the trend in the graph, when the glucose concentration is 2gm per 35ml of water, the rate of yeast respiration is the highest. When the glucose concentration is 4gm per 35ml of water and 6gm per 35ml of water, the rate of respiration decreases.

Regarding the consistency of trial results, at 2g and 4g glucose content, there were some inconsistency in the trial results. However, at 6g glucose content, the results of rate of respiration were more consistent.




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