Yeasts (Fig. 1 and 2) are a type of single-celled fungus often used to ferment alcohol. It is a heterotrophic organism, meaning the cells use energy produced by processing other organic materials. Heterotrophic organisms use cellular respiration to acquire this energy. This process is vital: it converts large, unusable energy molecules such as glucose into a more useful form of energy, adenosine triphosphate (ATP), which allows essential cellular activity to occur. Most yeast species are readily capable of using aerobic respiration to gain energy. when oxygen is available. This method produces carbon dioxide, water and energy. It is also very efficient, producing 36 molecules of ATP for each molecule of glucose: C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP. If oxygen is not readily available, yeast will use an alternative pathway (Fig. 3), from which ethanol, carbon dioxide and energy are produced. This is called anaerobic fermentation. It occurs about a hundred times faster than aerobic respiration; it is capable of producing only two molecules of ATP for every six molecules of glucose: C6H12O6  2C2H5OH + 2CO2 + 2ATPGlycolysis occurs initially through a sequence of enzyme-catalyzed reactions in the cytosol of a yeast cell. The high energy carbon bonds in glucose are broken and the lower energy molecule Pyruvate is formed. This produces enough energy to form ATP from ADP and phosphate (Pi). NAD+ is reduced to form the coenzyme NADH:C6H12O6 + 2NAD+ + 2ADP + 2Pi →2CH3COCOO− + 2NADH + 2ATP + 2H2O + 2H+NAD+ is then regenerated from NADH so that glycolysis can continue to occur. The lost electrons reduce the pyruvate, which is then converted to acetaldehyde. Two CO2 molecules are released as waste. Acetaldehyde is then converted to e...... middle of paper ......ose, lactose) to observe which produces the greatest and least amount of energy. Different concentrations of glucose or different temperatures of the glucose solution could also be used as an independent variable to establish the most effective concentration or temperature. It could also be relevant to measure the thermal energy produced by aerobic respiration of yeast by constantly bubbling oxygen gas through a glucose solution. Similar calculations could be carried out to compare the theoretical and practical energy produced.ConclusionThe hypothesis was accepted: the temperature of the yeast solution containing glucose did increase due to the fermentation of glucose by the yeast. The theoretical energy produced from glucose was lower than the experimental result; This is because not all the chemical energy has been converted into thermal energy.