Glycolysis and Fermentation in Yeast Abstract

Glycolysisand Fermentation in Yeast


Themain purpose of this experiment is to evaluate the glycolysis processand the fermentation process in yeast. Typically, glycolysis is abiological process that involves various enzymes, and it occurs inall living organisms. Primarily, it involves the breakdown of glucoseto ATP while leading to the formation of other by-products. Yeast iscapable of the fermentation process, and thus, this experimentevaluates its ability to catalyze this process. Additionally, weshould understand that both fermentation and glycolysis are anaerobicprocesses, and they begin with the sugar glucose. This essay alsodiscusses some of the basic materials that are required for theglycolysis and the fermentation processes to occur. Also, we shouldtake into account that the particular favorable conditions for theoccurrence of this processes will also be discussed conclusively. Forinstance, different reagents that were used in the whole process willbe noted in this section. In the long run, there is need to recordthe results of the experiment. The results will be tabulated for allthe numerical results regarding the formation of CO2. Other resultssuch as the color change will also be recorded in this section. Afterthe results are recorded, they will then be discussed and theultimate evaluation of the results will be determined here. It isalso in this section that that the final discussion and conclusion ofthe experiment will be drawn.

Classically,every cell in the body of living organisms’ respites/converts theenergy that is normally stored in the molecules that they consumesuch as proteins, carbohydrates and lipids. The cells convert theminto stored energy, and that is normally readily available to performany functions in the body. Some of the functions of the energyproduced in these processes include cell movement, active transport,synthesis of other molecules and muscle contraction among others.Therefore, it is evident that this process is crucial for thefunctioning of the body.

Glycolysisrefers to the biological process that involves breaking downsubstrate, in most cases glucose, to simpler molecules with ATP(Adenosine Triphosphate) as the ultimate product. Typically, thisprocess occurs in all living organism, and it’s a primary processin the production of energy. This makes both glycolysis andfermentation crucial in the living organisms by the fact that theyhelp in the product of energy in the form of ATP that is primarilyused in the body. Fermentation and glucose are both similar in thatthey all occur in anaerobic conditions and that their first ten stepsare also similar. It is crucial to note that the two processes differin the final products of the whole process. In glycolysis, there isthe conversion of glucose to pyruvate that is later converted tolactic acid through the lactic acid cycle. On the other hand, infermentation, it begins with the conversion of glucose to pyruvicacid that is subsequently converted to ethanol and Carbon Dioxidegas. The study of these processes is crucial since it enables us tounderstand the mechanism of production of energy in humans, animalsand other living organisms. it also helps as in the development ofthe countermeasures of the deficiencies in the energy in any livingorganisms. This is because one understands the absorption and theusage of the energy within the body and thus can manipulate theprocesses involved.

Thisexperiment aims at evaluating the ability of yeast to metabolize inthe presence of various sugars. Yeast is a component of theenvironment, and there are various types of yeast. Specifically, thisexperiment will use the baker’s yeast. It is of the strainSaccharomyces cerevisiae, and it is abundant in nature since itoccurs on the surfaces of the berries and sugars where it can easilyobtain sugars. It is crucial to note that this strain of yeast canmetabolize in the presence or absence of oxygen/aerobically oranaerobically depending on the availability of molecular oxygen.

Materialsand Methodology


Someof the materials and reagents for this experiment include One day oldliquid yeast living culture, 370C water bath. For the solutions, 2%of the following solutions were used: sucrose, galactose, lactose,fructose, maltose, starch and ribose. Some of the crucial chemicalreagents included: 0.01 M NaF, 0.001 M NaF, O.2 M MgSO4, 0.05 M NaF,0.20 M NaF. Other materials included small plastic rulers, large andsmall test tubes, marking pen and test-tube rack.


CarbohydrateUse in Glycolysis by Yeast

Ninelarger test tubes and nine smaller test tubes (which fit the largertest tubes) were obtained at the start of the experiment. The lengthof the small test tubes was then divided into three sections that areequal then they were labeled using a wax pencil. Both the nine largeand small test tubes were labeled 1 to 9 using a pencil. In the caseof small tube 1, the tube was filled to the 1/3 mark with liquidyeast culture then it was freshly mixed by swirling then it wasfilled subsequently with water. In the case of tube 2 to 9, they werefilled to the 1/3 mark with freshly swirled liquid yeast culture thenthey were topped up to the 2/3 mark with distilled water.Subsequently, the small tubes 2 to 9 were filled were then filled tothe rim with the appropriate substrate, either sugar or starchsolution. In a nutshell, the tubes were put in this order:

Tube1. Yeast + water + water

Tube2. Yeast + water + glucose

Tube3. Yeast + water + fructose

Tube4. Yeast + water + galactose

Tube5. Yeast + water + sucrose

Tube6. Yeast + water+ lactose

Tube7. Yeast + water + maltose

Tube8. Yeast + water + ribose

Tube9. Yeast + water + starch

Afterthat, the large tubes were then placed on their corresponding smalltubes. The anaerobic chambers were then inverted 2 to t3 times sothat the content could be thoroughly mixed and after this mixing,they were then left inverted, and this made the little air bubbles tobe trapped at the top of the small tube. The size of each smallbubble was then measured in millimeters then the values were recordedin a table (table indicated below). After that, all the anaerobicchambers were then placed in the 370C water bath carefully withoutletting the water level of the water bath get close to the tops ofthe tubes. The rack of tubes was then removed after 90 minutes (oneand a half hours) then the final size of the bubble was recordedimmediately. The difference in size was due to the production of gas(carbon dioxide).


Tube no


Initial vol. of bubble (mm)

Final vol. of the bubble (mm)

Rate of production of CO2 in mm of CO2 / hour














































Graphof change in volume (mm) against rate of CO2production


Magnesiumion concentration

Sevensets of large and small test tubes and then they were labelled from10 through 16. These test tubes contained:

Tube10. Yeast + water

Tube11. Yeast + water + glucose

Tube12. Yeast + 0.001 M NaF + glucose

Tube13. Yeast + 0.01 M NaF + glucose

Tube14. Yeast + 0.05 M NaF+ glucose

Tube15. Yeast + 0.20 M NaF + glucose

Tube16. Yeast + 0.2 M MgSO4+ glucose

Thesmall tube 10 was then filled to the 1/3 mark with the liquid yeastculture that was freshly mixed by swirling and then it was filled tothe rim with distilled water. The small tube 11 was then filled tothe 1/3 mark with the yeast culture then it was topped up to the 2/3mark using distilled water. After that, the small tubes 12 to 16 werefilled to the 1/3 mark with the yeast culture that was freshly mixedby swirling then they were topped up to the 2/3 mark by theappropriate NaF or MgSO4 solution. In the long run, the small tubes22 to 16 were then filled with the glucose solution that was addedlast. After they had been filled, the correspondingly numbered largertest tubes were quickly placed over the small test tubes. They werethen inverted to mix it then, at last, they were left inverted. Thesmall air bubbles were then tapped and then there sizes were quicklymeasured and recorded. The rack of the anaerobic chambers was thenplaced in a water bath at 370C without letting the level of water inthe water bath to come closer to the top of the tubes. After one anda half hours the rack was removed, and the final size of the airbubbles was recorded once again. The table below is a recording ofthe values of the bubbles that were measured:


Tube no

Test solution (yeast + )

Initial bubble size in mm

Final bubble size in mm

Rate of CO2 Production in mm of CO2 /hour







Glucose + water





Glucose + 0.001 M NaF





GLUCOSE + 0.01 M NaF





Glucose + 0.05 M NaF





Glucose and 0.20 M NaF





Glucose + 0.20 M MgSO4




Graphof the change in volume against the rate of the reaction


Analysis,Discussion and Conclusion

Inthe first experiment (carbohydrates use in glycolysis by yeast) thetest tube 1 is filled with the liquid yeast solution and then toppedup to the top without any substrate. This is a control experimentthat determines the action of the yeast on a sample of water.Consequently, there is no change in the volume of the air bubble inthis since no glycolysis/fermentation takes place and thus, there isno formation of any product of gas. Thus, there is no change in thefinal volume.

Itis also the same case in ribose and starch samples whereby there wasno significant change in the size of the final size of the airbubble. It is crucial to note that starch and glucose are the storedforms of glucose, and they cannot be broken down by yeast. Therefore,no respiration takes place in this case since yeast is unable tobreak down molecules of this conformation. Subsequently, for thismolecule to respired, there is need first to break them down toglucose that can then be acted upon by yeast. As a result, noreaction occurs in the case of starch and ribose and no gas is formedand in turn, there is no change in the size of the air bubble.

Inother cases such as that of maltose, there is the slow formation ofthe gas which means a slow rate of the reaction. This is because itis converted slowly to form glucose that then undergoes glycolysis toform the gas. It is also to note that other substrates such asglucose and lactose recorded a higher change in the volume of thebubble. This is because yeast readily acts on them and the formationof the gas is rapid in these cases since they are in the requiredconformation, and they do not need any conversion.

Finally,there is the quick measurement of the initial and the final volume ofthe bubble. This is important since the difference in the tworepresents the amount of carbon dioxide that was released in thecourse of the reaction thus the rate of conversion of the sugar toethanol and carbon dioxide. From this point, it is possible todetermine the rate of the entire reaction and, in turn, the action ofthe yeast on the different sugars. In conclusion, it can be derivedthat yeast glycolysis and fermentation in yeast using carbohydratesas a substrate is a scientifically proven process.

Inthe second case, there is no change in volume in tube 10. It is thecontrol experiment with no substrate and in turn, yeast has nothingto act on. Therefore, no change in volume is noted. A significantincrease in the final volume is also noted from tube 12 to tube 16.This is by the increase in the concentration of the sodium fluoride(NaF). The increase is because the activity of yeast increases withthe rise in molarity/concentration of this reagent. An increase inthe activity of yeast will, in turn, increase the formation of thegas and thus the increase in the volume of the air bubble. Thehighest gas formation is recorded in the case of yeast, glucose andmagnesium since magnesium is a good co factor for the enzymes of thisprocess and thus, a rapid reaction is experienced. Lastly, glucosewas added last since reaction entirely depends on the presence of thesubstrate. Therefore, in case it is put first, it will be depletedbefore the timer starts and much gas would escape and the resultsobtained will in turn not be valid.

Besides,it is crucial to note that in both cases the set up was left invertedfor 90 minutes to give the reactants to react conclusively andformation of products to occur. The set up was also placed in awater bath at 370C for cooling the set up since much heat isgenerated in this process. The inverted position helps to collect thegas since it will float after it is formed.