biology-Photosynthesis and Respiration

26 Jun biology-Photosynthesis and Respiration

Question
Photosynthesis and Respiration

Margaret E. Vorndam, M.S.

Version42-0103-00-01

Lab Report Assistant

Thisdocumentisnotmeanttobeasubstitute for aformallaboratoryreport.TheLabReport Assistantissimplyasummaryoftheexperiment’squestions,diagramsifneeded,anddatatables that shouldbeaddressedinaformallabreport. Theintentistofacilitatestudents’writing oflab reports by providing this informationin an editable filewhich can be sent to an instructor.

Observations

Data Table 1: Rf Value Comparison for Chlorophyll Pigments

Chlorophyll

Pigment

Observed

Color

Distance to top ofpigment,mm

Rf

Other Students’ Rf

Average

# of Rf Results Averaged from other Students (N)

Top of Solvent

Front

Carotenoids

Xanthophylls

Chlorophyll a

Chlorophyll b

Distancetotopofpigment,mm:Measurefromwherethetopofthesolventextractlevel

intersectedthepaper chromatographtothetopmostlevelofthecolor.Thenmeasurethis

distance to the top of the solvent front and record.

Data Table 3: Gross Photosynthesis in Elodea

Rates

Distance of travel, mm

Net Photosynthesis Rate over 10 minutes

= mm of movement from marked beginning point on bent

tube to end point after10 minutes

RespirationRate over 10 minutes

= mm of movement from marked end point on bent tube

toward beginning point after10 minutes

Gross Photosynthesis over 10 minutes

(= mm Net Photosynthesis + mm Respiration)*

Rate of Photosynthesis over one hour

(= Gross Photosynthesis ÷ 10 minutes x 60 minutes)

*Was respirationoccurring during photosynthesis? Add back the O2that was consumed by plant respirationto obtain the total photosyntheticrate.

Data Table 4: Comparison of PhotosyntheticRate

My PhotosyntheticRate Result

Average of Other Students’ PhotosyntheticRate

Results

N = (number of data averaged)

Data Table 4: Observationof pH Change in the Oxygen Cycle

Contents of

Respirometer

Initial

Color

T0, minutes

Final

Color

T1,minutes

Total timefor color change,

T1– T0,minutes

Elodea,

Bromothymol blue

solution

Elodea, Bromothymol blue solutionin foil

Data Table 5: Comparison of PhotosyntheticRate

My Result: Total timefor color change,

T1– T0,minutes

Average of Other Students’ Results: Total timefor color change,

T1– T0,minutes

N = (number of data averaged)

Elodea, Bromothymol blue solution

Elodea, Bromothymol blue solutionin Foil

Exercise 1: Chlorophyll Pigments

Results

Rf = distance to top of pigment in mm ÷ distance to top of solvent front.

Rf Average = average of other students’ Rf values, if available.

1. Rfvaluesarecalculatedratios ofhowfaramoleculemovedupthepaperchromatographas comparedtothelengthofthesolventfront.Thesevaluesaretypicallyequivalentformultiple trials.Calculate your Rf values based on your paper strip results, and record them inTable 1. The Rf value of the solvent front will always = 1.0, since Rf is a ratio.

2. Construct a stacked bar graph to demonstrate how the Rf value and the chlorophyll pigment are related.They-axiswillrepresenttheRfscalefrom0.0to1.0.Onthebargraph,labelthe calculated Rf with the name of the associated chlorophyll pigment. When complete, the bar graphshouldclosely resembletheactualchromatograph.Include astackedbargraphforyour results plusanother stacked bar graphnext to your graphwith your classmates’ averaged values.

Questions:

A. Identifytheareasofpigmentsthatyouobserveonthefilterpaper.Aretheylocatedinthe order that you expected?

If not, why not?

B. Compareyourpaperstripresultstotheresultsoftheradicchio paperstripsbelow.Arethe same pigments present in radicchio leaves?

If not, which chlorophyll pigments are missing?

How might you have guessed that this might be the case?

.

Example of Results Obtained from Radicchio

.jpg”>Paper Chromatograph

Radicchio Paper Chromatograph, dried and marked in preparationfor Chlorophyll Pigment Rf determinations

.jpg”>

Discussion

A. Was the initialhypothesis supported or refuted? Explain.

B. If you do not see separate bands of color on the filterpaper, what might you conclude?

P.

C. What might explain why the separationof the colors occurred?

D. Howdoyourvaluescomparetoyourclassmates’valuesforthesamepigmentsonTable1and in your graph? If they are not similar, what may be the reason?

.

Exercise2:ConversionofLightEnergytoFoodby

Plants

Questions

A. What molecule was produced by the Elodea while it was exposed to light?

B. Which organelle(s) in the plant cell is responsible for this reaction?

C. From where was this molecule derived?

D. What was the purpose of the light?

F. Which organelle was responsible for this reaction?

G. SetupatablesimilartoDataTable3:ComparisonofPhotosyntheticRateintheLabReport Assistantsection. CompareyourRateofPhotosynthesistotheaverageratesreportedbyother students in Table 3, if possible. How similar was your result to theirs?

H. Nameatleastthreeexperimentalvariables thatcouldexplainwhyyouroutcomemightvary from that of other students or from your own, if you repeated the experiment.

I. How could one determine how much oxygen is produced by the plant in one hour?

1. From geometry, recall that Volume =?r2h,where r = inside radius of a circle, or here the inside of the tube, and h = length of the movement, which means ? x radius squared

x height. Since the radius is ½ of the inside diameter, this equationis equivalent to

= 3.1416 x (inside diameter of the bent tube in mm ÷ 2)2x height (equivalent to the

distance that the solutiontraveled) = volume in mm3.

2. To convert mm3 volume to uL (typically the volume specification used at this level of measurement), use the conversion factor of 1 mm3 = 1 uL. Do thecalculationtodetermine thevolumeofoxygenthatisproducedbytheplantinone hour.

.gif”>3. How long would the plant need to photosynthesize to produce one liter of O2?

Discussion

A. Did this experiment support or refute your initialhypothesis. Explain.

B. Chlorophyll gives plant leaves their green color, (or red, in the case of radicchio, since it lacks a pigment that is typically present in green leaves). Research light and color, and hypothesize whetherchlorophyllabsorbsgreenlighttoanyappreciableextent.Proposeanexperimentsimilar to the one that you just performed that could be used to support your hypothesis.

C. There is current controversy as to whether the atmosphere is warming due to the burningof fossil fuelsandthe destructionoftherainforests(the GreenhouseEffect).Howdoesphotosynthesis and respirationrelate to this controversy?

D. Why are the tropics particularlyimportant to oxygen production?

Therefore, why should you support actionsthat reduce the cuttingof rainforests?

E. While thisexercisehasaddressedoxygenproduction, what otherimportantproductsresult from photosynthesis?Hint:Beside theproduction ofoxygen,whyareallanimals dependenton plants?

Exercise 3: Respirationin Plants

Questions

A. Why is the Elodea rinsed in distilledwater?

B. What gas did you add to the Bromothymol blue solution?

How do you know? Respirationis our primary form of energy production.

C. Why did the color turn more green-yellow or yellow when you breathed into it?

D. Write an equationfor the reactionthat explains the color change.

E. Whatcolorchangeoccurred afteryouplacedtheElodeainthetesttubeandturnedthelight source on/off?

.

F. What gas is produced and responsible for this change?

G. What gas is being removed?

H. What process is occurring in the firsttrial without the aluminum foil?

I. Whatdidyouobservewhenyourepeatedtheexercisewiththetesttubecontainingthe

Elodea wrapped in aluminum foil?

.

J. What gas is produced?

What term could be applied to the second trial?

K. Which process took longer?

Why?

Discussion

A. HowdidthetimeforcolorchangevarybetweenwhentheElodeawaspresentinthetesttube

(trial 1) versus when the Elodea was wrapped in aluminum foil? What might explain this?

B. Why do both plants and animals respire?

Would life in either group be possible without respiration?

C. Was the initialhypothesis supported or refuted? Explain.

D. HeatingcausesaBromothymolblueindicatorsolution tochangefromyellowtobluevery rapidly without a plant present. What explains this reaction?Howdid you control for heat in this exercise?

E. Setupadatatablesimilar toDataTable5:ComparisonofPhotosyntheticRateintheLabReportAssistantsection.Compareyourresultstothoseofyourclassmates,ifavailable,inTable

5. Were your results similar? What trends do you observe between the two trials?

F. Explainwhyyourdatamayhavedifferedfromthatofotherstudents.Whatvariablescould explain this difference?

G. HowwouldyoubeabletochecktoensurethatitwastheElodeaplantthatfacilitatedthe color change and not some other factor?

H. Howdoplants,suchasPinedrops,Pterosporaandromedea,ortheGhostPlant,Monotropa uniflora,that are not photosynthetic,make their food?

Do they respire?

Laboratory Summary

What have you learned from doing this laboratory?