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The Effect of Temperature on the Anaerobic Respiration of Yeast

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Essay, Pages 15 (3549 words)

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Essay, Pages 15 (3549 words)

Aim:

To investigate the effect of temperature on the rate of respiration in a suspension of yeast Saccharomyces cerevisiae.

Background Knowledge:

Yeasts are a form of eukaryotic microorganisms classified in the kingdom Fungi, with approximately 1,500 species known. They reproduce asexually by budding mainly, although some species reproduce by binary fission.

They are unicellular, although some species with yeast forms may become multicellular due to way in which they normally reproduce. Typically the size of a yeast cell is approximately 3-4 �m in diameter but this can vary greatly depending on the species.

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The yeast species Saccharomyces cerevisiae has been used in baking and fermenting alcoholic beverages for thousands of years. It is also extremely important as a model organism in modern cell biology research, and is the most thoroughly researched eukaryotic microorganism. Researchers can use it to gather information into the biology of the eukaryotic cell and human biology.

These microbes are thought to be one of the first domesticated organisms.

People have used yeast for fermentation and baking throughout history. Archaeologists digging in Egyptian ruins found early grinding stones and baking chambers for yeasted bread, as well as drawings of 4,000-year-old bakeries and breweries.

It has many uses in the production of certain products , these include; Alcoholic beverages, Beer, Root beers, Soda, Distilled drinks, Wine, Baking, Bioremediation (process that uses microorganisms, fungi, green plants or their enzymes to return the environment to its original state), Nutritional supplements, Science and Probiotics (dietary supplements).

Yeasts are chemoorganotrophs as they use organic compounds as a source of energy and do not require light to grow.

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The main source of carbon is obtained by hexose sugars such as glucose and fructose, or disaccharides such as sucrose and maltose.

They will grow from 10�-37�C, with optimum temperature in the range of 30�-37�C, depending on the species. There is little activity in the range of 0�C-10�C. Above 37�C yeast cells become stressed and will not divide properly.

Anaerobic respiration occurs when no free oxygen is present to remove the hydrogen. This therefore means the electron transport chain cannot continue to function and no more ATP can be produced via oxidative phosphorylation. Hence why a form of respiration is required without the need for oxygen.

Anaerobic respiration or fermentation as it is called when referring to some plant species (including yeast). This process does not require oxygen. Instead of oxygen reaction with the hydrogen to continue the processes such as the electron transport chain and oxidative phosphorylation, another substance is used. The hydrogen produced from the reduction of NAD is converted to ethanal. This frees up another NAD which allows glycolysis to continue. Read about anaerobic respiration in yeast experiment (temperature)

Pyruvate is firstly decarboxylated to ethanal, which in turn is then reduced to ethanol. This process is done by an enzyme called alcohol dehydrogenase. This process from glucose to ethanol is referred to as alcoholic fermentation.

The difference between anaerobic respiration and fermentation is the ability to recover from the effects. In anaerobic respiration the lactate build up can be removed in oxygen debt. 20% is oxidized in the liver, and the remaining 80% is converted to glycogen. However the effects of fermentation are permanent.

Enzymes are fundamental to all metabolic pathways in respiration and anaerobic respiration, especially key in the ethanol pathway, whereby ethanal is converted to ethanol via an enzyme called alcohol dehydrogenase.

The lock and key mechanism describes enzyme catalyzed reactions. Similar to the role of alcohol dehydrogenase in the fermentation of yeast.

The lock and key theory has substrate molecules and enzymes. All enzymes are a specific shape. There fore the substrate molecule must also have a specific shape for an enzyme to be able to react with it. This is known as the active site. For this reason the lock and key mechanism is known as substrate specific. For a reaction to take place, a compatible substrate molecule and enzyme must come together. The enzyme locks into the substrates active site and the required reaction takes place.

There are many factors in which enzymes can be effected by environment however, such factors which can inhibit and in fact stop the enzyme catalyzed reactions from occurring. These factors therefore have an effect on the metabolic pathways involved in anaerobic respiration.

Temperature can have a positive and negative effect on enzymes. All enzymes have an optimum temperature at which they operate. This temperature is often the stage at which enzymes are most productive. Within the human body this usually between 30�C and 40�C.

However if the temperature becomes too high or too low the reactions they carry out can be prevented. If the temperature is too low not many, if any, of the substrate molecules and enzymes collide with each other, meaning no reaction can take place or the rate of reaction is greatly reduced. On the other hand if the temperature is too high then this can cause denaturing of the enzymes. This means that the shape of the active site can change within some, or possibly all, of the enzymes. This therefore means that the substrate molecules can no longer fit into the active site, and due to the fact that enzyme catalyzed reactions are substrate specific, no reaction will occur.

Another factor effecting enzyme catalyzed reactions is the pH of the environment. Enzymes, like with temperature, have an optimum pH. This optimum however varies greatly depending on the enzyme. The optimum pH is the stage at which the enzyme will work most efficiently.

On a really general level, a lot of enzymes are most productive in slightly acidic pH levels. But often if the pH is very strongly acidic or alkaline then the enzymes can become denatured. Similarly with extreme temperatures the shape of the active site can be changed. This means that the substrate specific reactions cannot take place and the rate of the reaction can be severely slowed or in some cases stopped completely. This therefore could affect the metabolic pathways if the pH conditions are too severe.

Another factor affecting the rate of enzyme controlled reactions is the concentration of enzymes and the substrate concentration. This is dues to the collision theory. The collision theory states that a reaction occurs when particles collide. Therefore the amount of particles within a solution will effect the rate of reaction.

If there is a high concentration of enzymes and substrate molecules then the rate of reaction will be fast according to the collision theory. This is because there is a greater chance of particles colliding and so reacting. The opposite happens if the concentration of enzymes and substrate are low. The rate of reaction would be slow because there are fewer enzymes and substrate molecules, meaning there is less chance of a collision and so a reaction occurring.

Prediction:

I predict that as the temperature increases so will the respiration rate of the yeast. Knowing what I have researched. I believe that there will be little or no reaction at 0�C. This is because there will simply not be sufficient energy within the reaction to allow any collisions to occur. Also the enzymes involved in the reaction will not fit into the substrates active site. So I believe nothing will happen at this temperature.

At 20�C I predict that there will be some sort of reaction due to the fact that there is sufficient energy within the reaction to cause collisions and allow the enzymes involved to fit into the active site and react. However I do not think there will be a great deal of energy passed to the yeast so no dramatic results will be recorded at this temperature.

At 30�C I predict that there will be a greater rate of respiration than any previous temperatures as there is greater energy involved. This will cause more collisions to occur and allow the enzymes to react ore easily and regularly.

At 40�C or 50�C I predict that the most will occur at these temperatures. Not all the heat energy will be passed onto the yeast. Therefore if the temperature of surrounding water is 40�C or 50�C then there is the greatest chance of the optimum temperature of approximately 37�C being reached. This is when the most collisions will be occurring and the enzymes will be reacting most effieciently.

Finally at 60�C I predict that less carbon dioxide will be produced than 40�C or 50�C. However predict that respiration will still occur. Because not all the heat energy will be passed to the yeast, the temperature at 60�C will not be sufficient to completely denature the enzymes but will do to some, therefore slowing the reaction and ultimately the rate of respiration.

PRELIMINARY EXPERIMENT:

Introduction:

In this preliminary experiment the amount of carbon dioxide given off over a ten minute period will me measured. This will be done at three different temperatures, room temperature (approximately 20�C), 40�C and 50�C. The rates of reaction will then be measured and compared according to results.

Variables:

Factor

Effect

How it will be controlled

Temperature

Varied for individual parts of the experiment, but must remain constant when chosen. If not controlled then the rate of reaction may be different and results effected.

By adding cold and hot water to the water bath when necessary.

Yeast type

Different batches of yeast may have varying concentrations of enzymes within it. Causing variations in the rate of reaction

Use the same batch of yeast

Amount of Yeast

Different amounts of yeast could mean varying concentrations of enzymes within the yeast, causing large variations in the rate of reaction

Measure out the yeast from the same batch in equalquantities using a measuring cylinder

Water in Burette

If the water in the burette is not at the same level each time then inaccurate readings for displace water could be made

Same person fills the burette each time so measurments taken from the same place

Equipment:

Equipment

Use

Precision

Burette

Measure the water displaced

0.1ml

Water Reservoir

Allow for burette to be suspended in water

NA

Yeast Suspension

To be experimented on

NA

Water Baths

To keep water temperature constant

NA

Thermometer

Measure water temperature

1�C

Timers

Measure the time of the experiment

0.01seconds

Conical Flask

Hold yeast suspension

NA

Delivery Tube

To allow carbon dioxide travel to the burette

NA

Bung

Make the conical flask airtight

NA

Kettle

Boil water

NA

Diagram:

Method:

1. The equipment was set up as shown in the above diagram.

2. The kettle was switched on to allow the water to begin heating.

3. Just before boiling the water was then poured into the water baths and the temperature measured using a thermometer.

4. According to the temperature reading sufficient amounts of cold water were added to achieve the desired temperature.

5. The temperatures used in this preliminary experiment were Room Temperature (approximately 20 �C), 40�C and 50�C.

6. Once the required temperature was established a conical flask containing 100ml of yeast suspension was immersed in the water bath and the temperature was allowed to regulate for 10minutes, this was measured using a timer.

7. Once this 10minutes had elapsed the bung was put onto the conical flask and the tubing put up the burette to.

8. The respiring yeast was observed and measured for 10minutes further and the amount of carbon dioxide produced was recorded.

9. 3 repeats were done for each temperature.

10. Throughout the experiment certain amounts of cold and hot were added to the water bath to maintain a constant temperature.

Conclusion of preliminary experiment:

Overall I don’t believe that the preliminary experiment was particularly successful. The results recorded do not show any real particular pattern and even on the same temperatures so of the results vary considerably. This experiment has identified faults within the preliminary experiment and therefore created solutions and improvements to make sure the same mistakes are not mad on the real thing.

Evaluation:

Faults and improvements for the preliminary experiment have been identified and made. Firstly the way the temperature was maintain and achieved was not particularly effective or reliable. Boiling a kettle and using hot and cold water to keep a constant temperature doesn’t work well. It allows for too much variation in temperature and inaccuracies can develop from this. To improve this in the real experiment water baths with a temperature gage on them will be used. This means the water bath will contain metal plates within it, these are then heated to a certain temperature which can be set on the dial. This would mean that the temperature maintained was constant throughout and also the actual temperature would be closer to the real thing also.

Another problem was the range of temperatures observed. It wasn’t large enough and didn’t give full enough a range to properly analyse the results. In the real experiment a greater range will be used. From 0�C through to 60�C. This should hopefully give a larger range and therefore a better set of results to analyse.

MAIN EXPERIMENT:

Variables:

Factor

Effect

How it will be controlled

Temperature

Varied for individual parts of the experiment, but must remain constant when chosen. If not controlled then the rate of reaction may be different and results effected.

Water bath with selectable temperatures

Yeast type

Different batches of yeast may have varying concentrations of enzymes within it. Causing variations in the rate of reaction

Use the same batch of yeast

Amount of Yeast

Different amounts of yeast could mean varying concentrations of enzymes within the yeast, causing large variations in the rate of reaction

Measure out the yeast from the same batch in equalquantities using a measuring cylinder

Water in Burette

If the water in the burette is not at the same level each time then inaccurate readings for displace water could be made

Same person fills the burette each time so measurments taken from the same place

Equipment:

Equipment

Use

Precision

Burette

Measure the water displaced

0.1ml

Water Reservior

Allow for burtette to be suspended in water

NA

Yeast Suspension

To be experimented on

NA

Water Baths

To keep water temperature constant

NA

Thermometer

Meaure water temperature

1�C

Timers

Meaure the time of the expriment

0.01seconds

Conical Flask

Hold yeast suspension

NA

Delivery Tube

For gas to to travel to the burette

NA

Bung

Make the conical flask airtight

NA

Risk Assessment:

With this experiment there is not a great deal of risk. However goggles must be worn at all times as irritable substances may cause some damage if they come into contact.

Diagram:

Method:

1. The equipment was set up as shown in the above diagram.

2. Water was poured into the water baths and they were then set to the specific temperature.

3. The water was given time to regulate so the temperature was even throughout.

4. The temperatures used in this experiment were; 0�C, Room Temperature (approximately 20 �C), 30�C, 40�C, 50�C and 60�C.

5. Once the required temperature was established a conical flask containing 100ml of yeast suspension was immersed in the water bath and the temperature was allowed to regulate for 10minutes, this was measured using a timer.

6. Once this 10minutes had elapsed the bung was put onto the conical flask and the tubing put up the burette to.

7. The respiring yeast was observed and measured for 10minutes further and the amount of carbon dioxide produced was recorded.

8. 3 repeats were done for each temperature.

9. The results were observed and recorded.

Analysis:

Conclusion:

Overall I think that this was a successful experiment. The results show that as temperature increased the rate of respiration in yeast increased. This happened to an extent until around 50�C when some enzymes began to get denatured and the yeast cells began to die. There were a coupe of anomalous results recorded during the experiment, however these were very minimal. The anomalous results were also ignored when taking averages.

The results follow on from the basic principles of enzymes reacting at their optimum temperature most efficiently.

Discussion:

At 0�C nothing at all happened. No anaerobic respiration occurred within the yeast cells. This was due to the fact that there was not enough energy present in the reaction to cause any particles to collide and there was not enough energy present for the enzymes involved to function properly. This is consistant with what was said in the prediction.

At 20�C there was a reaction. However, the rate of respiration was fairly slow. This was because the amount of energy present in the reaction wasn’t particularly significant. Therefore the few collisions occurred and enzymes were functioning under stress. Making them less efficient and ultimately resulted in a present, but slow respiration rate.

At 30�C there is an increase in respiration rate. This is because there is more energy present than there was at 20�C. There for more particles collide and the enzymes can react with their specific substrates more easily and frequently.

Again at 40�C there is an increase in respiration rate. However it is not a significant increase. This suggests that the enzymes are still not quite at their optimum temperature. However as was the case at 30�C there is an increase in energy which causes yet more collisions and allows the enzymes to work more efficiently.

At 50�C there is a significant change in rate of reaction. This is because the enzymes have reached there optimum temperature range and are working at their most efficient. The enzymes fit into the active sites of its specific substrate molecules most easily and react with them at the fastest rate possible. Also at the optimum temperature the most collisions between particles occur, again increasing rate of reaction. I believe the optimum temperature has been reached because as the water is 50�C in the water some of the heat energy is absorbed by the glass of the conical flask. Therefore the actual temperature of the yeast itself is likely to be close to its optimum temperature range of 37�C -40�C. This is the temperature where the rate of respiration is highest. As was predicted.

At 60�C some of the enzymes have been denatured, therefore the amount of enzymes reacting has dropped. This ultimately means that the rate of respiration at 60�C is less than that of 50�C due to the denaturing of some of the enzymes.

The improvements that were made helped the reliability of the results as the repeats were a lot closer together in comparison with the preliminary experiment. The preliminary experiment did not follow the prediction at all, however after the improvements were made the experiment was much closer to what was predicted.

Evaluation:

General Comment:

I believe that after improvements were made to the preliminary experiment, the main experiment was very successful. I believe this because it followed closely to the prediction that was made, based on background knowledge. Also on the whole the results and repeats were very close together.

Anomalous Results:

Within the experiment there were a few anomalous results. On the results table they have been highlighted in yellow and they were not used when averages were calculated.

There is only one reason as to why these anomalies may have occurred. The tubing from the delivery tube. It was fairly thin and meant that a pressure build up was required for respired air to push through. It may have been the case that in these two occasions, the pressure build up had not been significant to push respired gas through, which would give an anomalous reading.

Limitations in the Procedure:

Overall the procedures in this experiment seemed quite successful and accurate. There were however one or two limitations:

The burette needed to be filled to exactly the right level each time. The only way this was done was by hand and eye. This meant that there is a possibility the water level at the beginning was different over repeats which could have an slight effect on the results.

Accuracy of Observations:

The same person was allocated to measure out all the liquids. This was done using a measuring cylinder to the nearest ml. The reason the same person was allocated to do this was so that the liquid was measured from the same point. Meaning each time there was exactly the same amount.

This was the same for reading temperature. One person observed the readings and recorded them to create unbiased results. Temperature was measured to the nearest degree.

The time of the experiments was recorded using a stopwatch. This can measure to the nearest 100th of a second.

Also when liquids were measured out throughout the experiment, the cylinders were dried. This meant that no excess water could mix or effect the amount of substance measured.

Main Source of Error:

I believe that the main source of error within this experiment was fact that a pressure build up within the delivery tube was necessary for the carbon dioxide to filter into the burette. This meant that carbon dioxide was being released at irregular times. In all but two cases in the results however, the amount of carbon dioxide given off was relatively similar and repeats were close. However due to the irregular release of carbon dioxide, spotting anomalies in the raw data was impossible. This meant that the only recorded anomalies are those that stand out at the end of the experiment.

Cite this essay

The Effect of Temperature on the Anaerobic Respiration of Yeast. (2020, Jun 02). Retrieved from https://studymoose.com/effect-temperature-anaerobic-respiration-yeast-new-essay

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