BackgroundSaccharomyces cerevisiae, more commonly known as baker’s or brewer’s yeast is a eukaryotic unicellular fungus used to make beer, wine, and bread.1 Likewise other biotic organisms, yeast requires energy for the cellular processes that occur within it, thereby undergoing cellular respiration.2 3 4 Cellular respiration is a series of reactions to convert simple sugars into energy.3 S.
cerevisiae can undergo alcohol fermentation, which is a form of anaerobic (takes place in the absence of oxygen) cellular respiration, or aerobic (takes place in the presence of oxygen) cellular respiration in order to form ATP (a molecule cells use for energy).2 Aerobic cellular respiration consists of series of reactions that require oxygen (except glycolysis, it is an anaerobic process); however, some organisms live in environments with a low supply of oxygen.2 3 Those organisms, such as yeast have been able to evolve to recycle NAD+.3 NAD+ is essential for glycolysis occur.3 If glycolysis stops, ATP cannot be produced and cell death will occur.
3 During anaerobic cellular respiration, simple sugars, such as glucose (C6H12O6) is broken down into two molecules of pyruvate (C3H4O3), producing a net of 2 ATP molecules, through the process of glycolysis.2 3 4 Then, each molecule of pyruvate is decarboxylated to ethanal (acetaldehyde), and carbon dioxide.4 5 After, the ethanal is reduced to ethanol and NADH is oxidized to NAD+.4 5 The NAD+ returns to the glycolytic pathway and the process starts over again.
4 explain why chose temperatures: to see at whichhow ph may affect labfast rising yeastdetermine at which temperature does yeast produce the highest of co2Personal engagement I decided to investigate the effect of temperature on the fermentation of yeast because I sometimes make bread with my grandma and occasionally the bread does not rise as much as we thought it would. Bread rises when the carbon dioxide produced by yeast form air pockets. Bread may not rise enough when temperatures are too low because then yeast would consume simple sugars too slowly, or when temperatures are too high because at high temperatures yeast start to denature. I was curious as to what temperature does yeast produce the most carbon dioxide and how different temperatures can affect yeast fermentation.AimThe aim of this investigation is to explore the effects of temperature (0.0°C, 10.0°C, 21.5°C, 35.
0°C, 40.0°C) on the fermentation of Saccharomyces cerevisiae (fast-rising baker’s yeast) by determining the concentration in ppm of carbon dioxide that the yeast produce under the various temperatures, while pH is controlled.Research questionHow do temperatures of 0.0°C, 10.0°C, 21.5°C, 35.0°, 40.0° affect the concentration in ppm of carbon dioxide produced by Saccharomyces cerevisiae (fast-rising baker’s yeast)?HypothesisIf then becausewhat results you would expect and why / the biological theory behind the expectationVariablesIndependent: The independent variable is temperature.
Water baths are maintained at temperatures (°C ± 0.5°C) of 0.0°C, 10.0°C, 21.5°C, 35.0°C, 40.0°C.
A thermometer is used frequently to measure the temperature to ensure that the temperature remains constant. Dependent: The dependent variable is the concentration of carbon dioxide produced by yeast measured in ppm (± 10 ppm) using a Vernier LabQuest and a carbon dioxide gas sensor. Controlled: The controlled variables are pH (± 0.5), quantity (0.20 g ± 0.
01 g) of Saccharomyces cerevisiae (fast-rising yeast), quantity (2.0 mL ± 0.05 mL) of glucose solution, concentration (1.00 mol/L ± 0.05 mol/L) of glucose solution, time (5.0 minutes ± 10 seconds) yeast is left in water bath before measuring the concentration of carbon dioxide, and time (30.0 seconds ± 1.0 seconds) for data collection.
*explainSafetyThere is a possibility for falls in the classroom. To prevent from falling, work area should be kept clean. Moreover, there is a risk for burns if contact is made with hot plates or heated glass. To ensure safety, tongs or oven mittens should be used when handling hot objects, and aprons should always be worn to protect from possible spills of hot liquid.
If burns occur, place affected area under cold water to soothe the pain. Furthermore, there is a possibility of broken glassware. To prevent from dropping glass, glassware should be handled properly and carefully; however, if glassware does break, do not attempt to clean up the glass without proper protection. To prevent abrasions, use a dust pan and a broom, or glass-handling gloves to clean up the glass. Goggles and close-toed shoes should be worn at all times to prevent injuries.
If abrasions do occur, clean the affected area with cold water and apply a band-aid. Moreover, there is a possibility of allergic reactions and digestive problems if Saccharomyces cerevisiae (yeast) is ingested.6 To prevent digestive problems, refrain from ingesting dry yeast. Active yeast is able to survive in the stomach and will break down sugar from food in stomach, produce carbon dioxide (CO2) and alcohol, and possibly causing alcohol poisoning and stomach pain.
6 In addition, the disposal of yeast down the drain should be avoided as yeast requires oxygen for decomposition, thus large quantities of yeast can increase oxygen demand of organisms in water, affecting aquatic life.7 An alternative is to dispose the yeast in the garbage.7 The glucose solution can be disposed down the drain after the investigation. Equipment600.00 mL beaker (± 0.50 mL)Electronic weighing scale (± 0.01g)Tongs or oven mittensThermometer (± 0.10°C)Plastic containerHot plateVernier LabQuestCarbon dioxide gas sensorStopwatch (± 0.
10 seconds)5.00 g Saccharomyces cerevisiae (fast-rising baker’s yeast)9.00 g glucose100.00 mL graduated cylinder (± 0.
50 mL) 50.00 mL distilled waterAssess to tap waterBag of ice Small tub50.00 mL (± 0.
50 mL) of 1.00 mol/L (± 0.05 mol/L) glucose solution ScopulaWeigh boat100.00 mL beaker (± 0.50 mL)DropperGlass stirrerParafilmpH paperProcedurePrepare 50 mL of 1 mol/L glucose solution:1 mol/L x 180g glucose/mol x 0.
05 L = 9 g glucoseScoop 9 g of glucose using a scopula onto a weigh boat on an electronic weighing scale. Pour glucose into a 100 mL beakerMeasure 50 mL of distilled water using a 100 mL graduated cylinder. Use a dropper for the last drops of distilled water. Pour distilled water into the same 100 mL beaker as the glucose.Mix glucose solution with a stirrer until glucose dissolves.
Cover the beaker with Parafilm when not using glucose solution to prevent contamination.Temperature set-ups:Prepare the Vernier LabQuest and carbon dioxide gas sensor to measure carbon dioxide concentration in ppm every second for 30 seconds. Prepare a water bath for yeast at 0°C. To do so obtain a 600 mL beaker and fill it with 400 mL of tap water. Obtain a small tub and fill it halfway with ice. Place the beaker into the tub and surround it with ice. Use a thermometer to ensure the temperature is at 0°C.
Add more ice if necessary. Maintain the temperature at 0°C by measuring the temperature regularly.Measure 0.2 g of Saccharomyces cerevisiae (fast-rising baker’s yeast). Pour yeast into a plastic container.Measure 2 mL of the glucose solution using a dropper and a graduated cylinder.
Pour the solution into the same plastic container as the yeast. Immediately close the plastic container (make sure it is airtight) and put the container into the water bath. Start stop watch. Incubate the plastic container in the water bath for 5 minutes. Measure temperature and swirl plastic container regularly.After incubation for 5 minutes, open the plastic container (make sure to still keep the plastic container in the water bath) and immediately insert the carbon dioxide probe and begin the LabQuest.
Data collection will end after 30 seconds. Record the initial and final concentration of carbon dioxide. Use pH paper to measure the pH. Record. Rinse plastic container with tap water to prepare for next trial.Repeat 3-8 for 4 more trials.
Repeat 2-9 for temperatures 10°C, 35°C, 40°C (use a hot plate instead of a tub of ice to prepare the water baths at these temperatures), and room temperature (record the actual temperature). Make sure to use tongs or oven mittens when handling hot glassware. ObservationsSaccharomyces cerevisiae (fast-rising baker’s yeast) are light brown in colour, fine, and granular. Results