9. Cellular Respiration in Yeast



9. Cellular Respiration in YeastHow does temperature affect the rate of cellular respiration in yeast? ObjectivesDescribe how temperature affects the rate at which living systems reorganize energy and matter.Materials and EquipmentData collection systemStirring rodOptical dissolved oxygen sensorHot plateWireless temperature link with fast response Activated yeast suspension, 45 mLtemperature probeDistilled water, 600 mLBeakers (3), 250-mLIce, 300 mLBeaker, 1-LMarking penGraduated cylinder, 25-mLWash bottle filled with distilled waterGraduated cylinder, 100-mLSafetyFollow these important safety precautions in addition to your regular classroom procedures:Wear safety goggles at all times.Handle the hot plate and hot glassware with care.Procedure1.Select Sensor Data in SPARKvue. 2.Connect the dissolved oxygen sensor and temperature link to your device. 3.Make sure the DO2 Concentration measurement from the dissolved oxygen sensor is checked along with the temperature measurement from the wireless temperature link. Do not select the temperature measurement from the dissolved oxygen sensor. Choose the Digits template.4.Remove the rubber cap from the dissolved oxygen (DO2) probe. Avoid touching the bottom of the probe. Tighten the metal cap at the end of the probe if necessary.455295058420Figure SEQ Figure \* ARABIC 1: Cool beaker in an ice bath0Figure SEQ Figure \* ARABIC 1: Cool beaker in an ice bath5.Label the three 250-mL beakers: room temperature, cool, warm. 6.Add 200 mL of room temperature distilled water to each 250-mL beaker.7.Fill the 1-L beaker to 1/3 of its volume with ice and water make an ice bath. Set the cool beaker in the ice bath so all 200 mL of distilled water inside the cool beaker contacts the ice bath as shown in Figure 1, but do not let water from the ice bath enter the cool beaker. Drain excess liquid from the ice bath if necessary.8.Place the warm beaker on the hot plate. Turn on the hot plate to a low setting, and allow it to warm to about 35?°C.465772586360Figure SEQ Figure \* ARABIC 2: Metal portion is submergedFigure SEQ Figure \* ARABIC 2: Metal portion is submerged9.Place the end of the temperature probe into the water in room temperature beaker. Do not allow the probe to contact the beaker. Observe the live temperature reading beneath the digit displays. When the reading stabilizes, record the water temperature in Table 1. 10.Rinse the temperature probe and set it aside. 11.Hold the DO2 probe in beaker 1 as shown in Figure 2. Do not allow the probe to contact the beaker and keep the metal portion at the end of the probe fully submerged until you are directed to remove the probe from the beaker. Do not let the sensor box get wet.12.Gently stir the water continuously with the DO2 probe for 30 seconds. 13.Stir the activated yeast suspension. Measure 15 mL of the suspension and pour it into the room temperature beaker. Stir to mix. 14.Select Start to begin collecting data. Record the initial DO2 concentration in Table 1. Continue to stir and record data for 2 minutes (120 seconds).15.Stop collecting data. Record the final DO2 concentration and the time elapsed in Table 1.16.Rinse the DO2 sensor and set it aside. 17.Drain excess liquid from the ice bath if necessary to keep ice bath water from flowing into the cool beaker. Repeat Steps 9-16 with the cool beaker. Leave the beaker in the ice bath while performing the procedure. 18.Repeat Steps 9-16 with the warm beaker. Leave the beaker on the hot plate while performing the procedure.19.Replace the rubber cap on the DO2 probe.20.Use the following equation to calculate change in DO for each run; record the result in Table 1.Change in DO2 = Final DO2 - Initial DO221.Use the following equation to calculate the rate of oxygen consumption by the yeast and record the result in Table 1.Rate of DO2 Consumption = Change in DO2 ÷ TimeData CollectionTable 1: Dissolved oxygen and temperature readings at different solution temperatures Temperature ConditionWaterTemperature (°C)Initial DO2(mg/L) Final DO2(mg/L)Time(s)Change in DO2 (mg/L)Rate of DO2 Consumption (mg/L·s)Room TemperatureColdWarmQuestions and Analysis1.In which temperature did the DO2 level decrease most rapidly? What does this indicate about the environmental needs of yeast? Support your answer with data.2.Why is oxygen consumption a good measure of respiration rate in yeast? Include a description of how oxygen molecules are consumed and recombined during cellular respiration.3.If oxygen is not present, respiration can still occur. What is that process called? What additional end products are produced?4.Explain the difference in the amount of energy produced in aerobic versus anaerobic respiration.5.Humans are warm-blooded mammals. If we measured respiration in humans, where would the rate of oxygen consumption be highest? Explain your answer. ................
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