Anaerobic respiration is an oxygen independent respiration process, meaning when oxygen is not present in the environment through this process an organism can produce energy. Here we are going to discuss all possible aspects regarding anaerobic respiration in yeast.
When oxygen is absent in the environment yeast starts to respire anaeribically. In this process sugar or glucose molecules undergo glycolysis and break into pyruvate. The pyruvate breaks down further , producing a small amount of energy with ethanol and carbon dioxide. This kind of respiration is known as anaerobic respiration in yeast.
Common yeast or Saccharomyces cerevisiae is one of the commercially most popular yeast species for its role in the fermentation process. Yeast has the ability to respire in both aerobic and anaerobic manner but When oxygen is absent in the environment yeast starts to respire anaeribically. It is also known as beker’s yeast.
Anaerobic Respiration from Wikimedia Commons
How does anaerobic respiration occur in yeast ?
Yeast are unicellular eukaryotic fungi, able to proceed cellular respiration in both aerobic and anaerobic manner.
When oxygen is present in the Cellular environment yeast goes for an aerobic respiration process and produces more energy. But if oxygen is absent in the environment yeast starts fermenting. For anaerobic respiration process the Glucose molecule (6-carbon molecule) undergoes glycolysis and breaks into 2 molecules of pyruvate (3- carbon molecule) . Later the pyruvate converts into organic alcohol Ethanol (2- carbon molecule), one carboxyl group releases as carbon dioxide molecule and a small amount of energy releases.
As in this process oxygen molecules are not involved in other inorganic molecules like sulphate, nitrate groups serve as the electron acceptor and release energy. This kind of phosphorylation process is less efficient than the oxidative phosphorylation process. Hence less amount of energy produced.
Where does anaerobic respiration in yeast occur?
Yeast is a unicellular eukaryotic fungi species. Having the ability to respire in both aerobic and anaerobic manner.
Anaerobic respiration in yeast occurs in the Cellular cytoplasm of the organism.
In the aerobic respiration process the first step Glycolysis takes place in the cytoplasm and the later steps from acetyl-CoA formation to oxidative phosphorylation all occur in the matrix of mitochondria.
When does anaerobic respiration occur in man and yeast?
There are two major kinds of anaerobic respiration processes found, such as lactic acid production and alcohol fermentation.
In man lactic acid production process is found and in yeast cell alcohol fermentation process is found.
In man lactic acid production process is found. During intense exercise or hard work the muscle tissue lacks sufficient oxygen in the cellular environment. To overcome this muscle cells start to respire anaerobically and produce energy. In this process the Glucose undergoes glycolysis and converts into pyruvate. The pyruvate further breaks into lactic acid and releases energy.
Glucose → Lactic Acid + Energy
C6H12O6 → C3H6O3 + Energy (2ATP)
Lactic Acid Production from Wikimedia Commons
In yeast when oxygen is absent in the environment, it starts to respire through the fermentation process. In this process sugar or glucose molecules undergo glycolysis and break into pyruvate. The pyruvate breaks down further , producing a small amount of energy (generally 2 molecules of ATP) along with ethanol and carbon dioxide.
Glucose → Ethanol + Carbon Dioxide + Energy
C6H12O6 → C2H5OH + CO2 + energy (2ATP)
Alcohol Fermentation from Wikimedia Commons
Anaerobic respiration in yeast equation?
The equation of anaerobic respiration in yeast-
Glucose → Ethanol + Carbon Dioxide + Energy
C6H12O6→ C2H5OH + CO2+ energy (2ATP)
The equation states that in one cycle of anaerobic respiration one Glucose (6-carbon molecule) molecule breaks and produce small amount of energy generally 2 molecules of ATP or adenosine triphosphate along with one molecule of ethanol (2 – carbon molecule) and one molecule of carbon dioxide ( 1-carbon molecule).
Anaerobic respiration in yeast experiment?
Usage of Saccharomyces cerevisiae or normal yeast is very popular economically due to its capability of producing alcohol from anaerobic respiration method. Let’s demonstrate the anaerobic respiration in yeast through a simple experiment.
Principle
Common yeast or saccharomyces cerevisiae is a unicellular eukaryotic fungi capable of respiring anaerobically in absence of oxygen molecules. During anaerobic respiration process yeast breaks Glucose molecules and produces some amount of energy along with organic alcohol (Ethanol) and Carbon Dioxide (CO2). This process is also known as the fermentation process.
C6H12O6 → C2H5OH + CO2 + energy (2ATP)
Materials required
- Yeast
- 60g water
- 30g Glucose
- Breaker
- Flask
- Thermometer
- Two holed cork
- Flame Burner
- Lime water or Ca(OH)2 (aqueous solution of Calcium hydroxide)
- Test tube
- Liquid paraffin
- Delivery tube
Procedure
- Pour the water in a beaker and add glucose powder in it.
- Heat it through a burner.
- Cool the boiled water without shaking it.
- Add yeast into the water
- Transfer it into the flask
- Add liquid paraffin into the flask
- Close the opening of the flask with a two holed cork.
- Insert a thermometer into the flask from one hole of the cork.
- Insert a delivery tube through the other hole.
- Adjust another end of the delivery tube into a test tube
- Fill the test tube by lime water
- Note initial temperature from the reading of the thermometer.
Result
After spending 24 hours we see that the temperature of the Glucose solution increases. The lime water in the test tube turns its colour into white milky colour. After opening the flask cork an alcoholic smell comes out from the solution.
Analysis
The increasing temperature of the solution indicates the energy production in the solution. The milky white colour of lime water signifies the release of CO2 or carbon dioxide from the Glucose solution. The alcoholic smell indicates the production of Ethanol in the sample solution.
Means the yeast in absence of oxygen (boiled water) involves anaerobic respiration producing energy along with ethanol and releases carbon dioxide CO2 from it.
To know more about anaerobic organisms read our article on 10+ Anaerobic Bacteria Examples :Detailed Explanations
Anaerobic respiration in yeast products?
During anaerobic respiration along with energy some reaction by-products are also produced.
The products produced during anaerobic respiration in yeast are 2 molecules of ATP or adenosine triphosphate, one molecule of ethanol (C2H5OH) and one molecule of carbon dioxide (CO2).
Pathway of anaerobic respiration in yeast
The anaerobic respiration pathway is not as complex as the aerobic respiration pathway. It doesn’t involve so many steps like Acetyl-CoA formation, Krebs cycle, etc. The anaerobic respiration pathway is very simple and produce energy along with organic compounds generally.
The pathway of anaerobic respiration in yeast involves two steps respectively-
Glycolysis
The first step in anaerobic respiration is the same as aerobic respiration which is Glycolysis. In this process the Glucose molecule (6-carbon molecule) breaks and produces some amount of energy, generally 2 ATP molecules along with 2 molecules of pyruvic acid or pyruvate (3-carbon molecule).
Transition reaction
It is the second and last step in anaerobic respiration. In this process the pyruvate converts into some organic compound, in case of yeast it is converted into ethanol and produces less amount of energy (2 ATP), releasing carbon dioxide from it.
To know more read our article on Anaerobic respiration : Is Fermentation Anaerobic Respiration:What,Why,Detailed Facts
How does anaerobic respiration differ in yeast and human cells?
Anaerobic respiration processes in yeast cells and in human cells are different from each other.
In yeast cells the anaerobic respiration process is generally the fermentation process which produces ethanol or some other alcohol as a by-product.
In the case of human cells the anaerobic respiration is generally a lactic acid production process in which lactic acid is produced as the by-product of the reaction causing sore muscles.
To know more read our article on Anaerobic respiration 4+ Anaerobic Respiration Examples : Detailed Explanations
As a whole we can say that anaerobic respiration of yeast plays a very significant role economically. We also discuss the pathway and steps of anaerobic respiration process in yeast. We see the difference between anaerobic respiration in yeast and in human cells. Hope it will be well informative to you.
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Hello, I am Piyali Das, pursuing my Post Graduation in Zoology from Calcutta University. I am very passionate on Academic Article writing. My aim is to explain complex things in simple way through my writings for the readers.
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