CellularRespiration

Needs an intro for fermentation.

Fermentation(20 minutes + 60 minute wait time)

Inthis activity youwillseetheactionof yeast cells on glucose and distilledwater.

1.Obtain2 Durham tubes, 2 beakers (100 ml), and 2test tubes pergroup.

2.Fill onebeakerwithhalf yeast solutionandhalfgrapejuice, make sure to mix well. Fill oneDurham tube and test tubewiththis mixture, using a dropper to max-fill. Invertthe Durham tubeand place it into thetest tubewiththegrapejuice, yeast mixture.No bubbleshould beintheDurham tube. This might take multiple tries.

3.Fill the second beaker withhalfyeast solutionandhalf distilledwater.FilloneDurham tubeand test tube withthis mixture, using a dropper to max-fill.Invertthe Durham tubeand placeit into thetesttubewiththedistilled waterand yeast mixture.

4.Label thetubes withyourgroupnameand place themina test tube rack in an incubator.

5.Allowexperiment toincubateforabout onehourorlonger, thenexamineand analyze results.

CellularRespirationandCarbonDioxideProduction:Using Carbon DioxideasanIndicatorof CellularRespiration

Carbondioxideis a byproduct of cellular respiration.Therefore, wecanmeasuretheamount ofcarbon dioxideas anindicatorof cellularrespiration. Whencarbondioxidecombineswithwateritformscarbonic acid. Bromthymol bluewill beused todetect anincrease incarbondioxideconcentration.Bromthymolblueis a pHindicator,which turns yellow whenthepHdecreases orbecomesmoreacidic. Inthis assignmentwewillconduct twoexperiments.

Experiment1(15 minutes)

Inthisexperimentyouwilldetermineifyourexhaledbreath containsagreaterconcentrationofcarbondioxidethanispresentintheatmosphere.

  1. Obtaintwo test tubesand add 2 ml of tap water and 3 drops of bromthymol blueintoeachtest tube.(This should be blue.)
  2. Blowinto test tube#1witha straw for1-3 minutes(carefulnot toblowtoohard and spill).
  3. Usea pipetteto pumpatmosphericairinto thesecond test tubefor2-3minutes.
  4. Record any color changes. (Should turn green in the presence of CO2)

Experiment 2 (This needs to sit for 24 hours or more)

Inthisexperimentyouwill determine ifgerminating beans produceagreaterconcentrationofcarbon dioxidethanis presentinthe air.

  1. Obtaintwo test tubes; add 2 ml of tap water and 3 drops of bromthymol bluetoeachtest tube.
  2. Put Durnham tubesinto thetesttubesto makea platform(to keepthebeans out ofthe solution).
  3. Intube #1 place1-3germinating beans.Intube #2 do not placeanything.
  4. Cover the test tubes with parafilm,put ina rack, andlet sit for 24 hours.
  5. Record any colorchanges andresults.

Fermentation

a.WhichDurhamtubecontainedmoregas?Why?

The test tube with grape juice contained more gas. The yeast oxidized the glucose in the grape juice to produce carbon dioxide.

b.Didtheaboveexperimentrequireoxygen?

The Fermentation experiment does not require oxygen because fermentation is anaerobic.

c.Whattypeofgaswascapturedinthe Durhamtube?

Carbon dioxide gas was captured in the Durham tube. The yeast oxidized the glucose in the grape juice to produce carbon dioxide.

d.Whatistheexperimentalvariableinthisexperiment(remembertheexperimentalvariableisthe factorbeingtested)?

Grape juice is the experimental variable.

e.What isthedependentvariable(rememberthedependentvariable iswhatismeasuredtodetermineiftheexperimentalvariablehasaneffect)?

Carbon dioxide gas is the dependent variable.

f.HowmanymoleculesofATPareproducedwhenglucoseismetabolizedduringfermentation?

During fermentation, only 2 molecules of ATP are produced.

g.Bread ismadebymixingflour,water,sugar,andyeasttoformdough.Whydoesthedoughrise?Whatcausedalltheconcavitiesinasliceofbread?

The yeast oxidizes the sugar in the dough and forms bubbles of carbon dioxide causing the dough to rise and air bubbles in the bread.

h.What “toxic” substanceisproduced whenvertebrates undergo fermentation?

Lactic acid is produced when vertebrates, such as animals undergo fermentation.

CellularRespirationandCarbonDioxideProduction

a.Recordthe resultsofyourexperimentsinthetablebelow. Carbondioxideproductioninhumansandgerminatingpeaseeds

ColorofbromthymolblueCO2Concentration after experiment (circleappropriate)

Experiment#1:HumanExpiration

Tube#1:ExhaledairYellowIncreasedNo Change

Tube#2:AtmosphericairBlueIncreasedNo Change

Experiment#2:GerminatingBeans

Tube#1:Germinating BeansYellowIncreasedNo Change

Tube#2:AtmosphericairBlueIncreasedNo Change

b.Whatisthepurposeoftube#2inexperiment1and2?

Tube #2 is the control in both experiments.

c.Whatconclusioncanyoudrawfromtheresultsofexperiment1?

Exhaled breath contains a greater concentration of carbon dioxide then is present in the atmosphere.

Whatconclusioncanyoudrawfromtheresultsofexperiment2?

Germinating seeds produce a greater concentration of carbon dioxide then is present in the air.

Materials

This lab uses germinating beans which requires advanced preparation.

1

Per Bench

Fermentation

  • 2 100ml beakers
  • 2 Durham tubes ( we used the extra small test tubes 10x75mm)
  • 2 Test tubes (the extra small test tubes need to fit inside)
  • 100 ml yeast solution
  • 50 ml grape juice
  • Distilled water
  • 2 transfer pipettes
  • Test tube rack
  • Marker

Cellular Respiration Exp. 1

  • 2 test tubes
  • Bromthymol blue
  • 1 straw
  • 1 pipette( 1ml or 5ml)
  • 1 pipettor

Cellular Respiration Exp. 2

  • Bromthymol blue
  • 2 test tubes
  • 2 Durham tubes
  • 1-3 Germinating beans
  • 2 pieces of parafilm

Per Class

  • 12 100ml beakers
  • 24 Durham tubes
  • 36 test tubes
  • 600ml yeast solution
  • 300ml grape juice
  • 6 bottles of distilled water
  • 12 transfer pipettes
  • 6 test tube racks
  • 6 markers
  • 6 bromthymol blue
  • 6 straws
  • 6 pipettes (1ml or 5ml)
  • 6 pipettors
  • 6-18 germinating beans
  • 12 pieces of parafilm

1