The Formula for the Yeast Fermentation Reaction - Essay Example

An investigation to find out the effect of respiration in yeast when sugar is added to flour-and-water dough Problem: - How does the concentration ofsugar affect the growth rate in yeast. Hypothesis: - As the concentration of sugar increases the growth rate of yeast also increases. Planning Apparatus: - flour, distilled water, 7 balloons, baker’s yeast, table sugar or sucrose, string , weigh boat, 2- 50 ml graduated cylinder, 600 ml beaker ,Overflow pan ,Permanent markers. The amount of sugar in each sample will be changed, keeping all other factors like amount of dough, temperature and other factors identical or same. The yeast derives its energy by fermentation, which is a type of anaerobic respiration. The formula for the yeast fermentation reaction is given below: C6H12O6 = 2CH3CH2OH + 2CO2 + energy, or glucose = ethyl alcohol + carbon dioxide + energy (King, T.J and Roberts, Michael. 1987). For the yeast cell, this chemical reaction is essential to produce energy for life. Alcohol and the carbon dioxide are waste products produced by the yeast. These waste products are of great utility value. This chemical reaction, known as fermentation can be observed and measured by monitoring the amount of carbon dioxide gas produced as a result of the break down of glucose. Safety Points Pilot experiment: - several bowls were taken and a mixture of dough and beakers yeast and sugar were placed in them. All conditions of the experiment were kept unchanged, with the exception of the amount of sugar, which was changed. It was observed that the number of bubbles in the dough were more if the amount of sugar was more. This indicates that there was greater active growth of the yeast where the sugar concentration was more. Obtaining Evidence Main experiment: - With the help of a plastic spoon or spatula some yeast is to be placed in a weigh boat on the balance and 10 grams of yeast is to be measured out. Next, using a separate weigh boat, 5, 10, 15, 20, 25, 30 grams of sugar are to be measured out. 50 gms of dough is to be kneaded by using same proportions of water and flour in separate weigh boats. Subsequently, a mixture of 10 grams of yeast and equal amounts of dough, thoroughly mixed, are to be placed in 7 balloons. The contents of these balloons are to thoroughly mixed once again. Then a piece of string is to be used in order to tie the balloon just above the mixture in it. This is to ensure that there is no air inside it. After this the balloon must be pressed gently from the sides in order to expel any air left inside and a tight double knot is to be tied with a piece of string. The excess string is to be left on the balloon. The rubber band is to be knotted as closely as possible to the knot in the string. These balloons are to be placed on ice in order to prevent fermentation. Similarly, all 7 balloons are to be prepared using the 0,5,10,15,20,25,30 grams of sugar. These balloons are to be labeled as A,B,C,D,E,F,G respectively. Next, their volume is to be determined using the water displacement method. In this method, a 600 ml beaker or large jar is to be placed in an overflow pan. This container is to be filled to the very top with tap water. The balloon is to be completely submerged in the water by pushing it under the water and allowing the water to spill over the sides and into the pan. This process is to be stopped when the fingers touch the water. The water in the pan is the volume of the balloon. This is to be measured carefully in a graduated cylinder and recorded on a data table. After this the balloon is to be put back in the ice immediately. It is sufficient to measure a single balloon’s initial volume as the initial volume of all the balloons will be almost the same as the extra sugar dissolved in the dough does not occupy appreciably more volume; hence the error introduced is negligible. The initial volume so obtained is observed to be 34 ml. After this the balloons are removed from the ice and the fermentation begins. After an hour the volume of the balloons are again measured using the water displacement method. These measurements have been indicated in table given below. These measurements are shown in the graph appended below the table. On the X – axis, the initial amount of sugar added to the dough in grams is plotted and on the Y – axis, the amount of CO2 produced in ml is plotted. Analysis of the Observations The data provided by this experiment proves the hypothesis to be correct, namely, that the growth rate in yeast increases with increase in concentration of sugar till a certain maximum concentration of sugar in the dough and then decreases. This decrease is due to the increase of the osmotic potential of the medium surrounding the yeast, which kills the yeast. Evaluation As indicated in the analysis of the observations section, data after a certain limit of sugar concentration has to be rejected, because the yeast starts dying and no growth takes place. This is due to the fact that water does not enter the yeast cells but leaves the yeast cells due to osmosis. List of References King, T.J and Roberts, Michael. 1987. Biology. Nelson Thornes. ISBN: 0174481350. p 66. Read More