Photosynthesis and Respiration MargaretE.Vorndam,M.S

QUESTION

Photosynthesis
and Respiration
MargaretE.Vorndam,M.S.
Version 42-0103-00-01

LAB REPORTASSISTANT

Thisdocumentisnotmeanttobeasubstitute foraformallaboratoryreport.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

Distanceto top of
pigment,mm

Rf

Other Students’Rf
Average

# of Rf Results Averagedfrom
other Students(N)

Topof Solvent
Front

NA

Carotenoids

Xanthophylls

Chlorophylla

Chlorophyllb

Distancetotopofpigment,mm:Measurefromwherethetopofthesolventextractlevel
intersectedthepaperchromatographtothetopmostlevelofthecolor.Thenmeasurethis
distance to the top
of the solvent front and record.

Data
Table 2: Gross Photosynthesis
in Elodea

Rates

Distanceof 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 O2 that was
consumed by
plant respirationto
obtain
the total photosyntheticrate.

Data
Table 3: Comparison of PhotosyntheticRate

My PhotosyntheticRate Result

Average of Other Students’ PhotosyntheticRate
Results
N=
(numberof dataaveraged)

Data
Table 4: Observationof pH Change in the Oxygen
Cycle

Contentsof
Respirometer

Initial
Color

T0, minutes

Final
Color

T1,minutes

Total timefor
color
change,
T1– T0,minutes

Elodea,
Bromothymolblue
solution

Elodea, Bromothymolblue
solutionin Foil

Data
Table 5: Comparison of PhotosyntheticRate

My
Result: Total timefor
color
change,
T1– T0,minutes

Averageof
Other Students’Results:
Total time
for color change,
T1– T0,minutes
N=
(numberof dataaveraged)

Elodea, Bromothymolblue solution

Elodea, Bromothymolblue solutionin Foil

Exercise
1:ChlorophyllPigments
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?

.0/msohtmlclip1/01/clip_image002.jpg”>B. Compareyourpaperstripresults
totheresults
oftheradicchiopaper strips below. Are
the same pigments present
in radicchio leaves?

If not, which
chlorophyll pigments are missing?

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

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?

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?

E. What
molecule was produced by
the elodea while it was wrapped in aluminum foil? F. Which organelle was
responsible for this reaction?
G. Setupatablesimilar
toDataTable3:ComparisonofPhotosynthieticRateintheLabReport
Assistant section. Compare
your Rate of Photosynthesis to
the average rates
reported by other students
in Table 3, if possible. How similar was your
result to theirs?

H.
Nameatleastthreeexperimentalvariablesthatcouldexplainwhyyouroutcomemightvary
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?

.0/msohtmlclip1/01/clip_image004.gif”>1. From geometry,
recall
that Volume =
Pr2h, where
r=
insideradius
ofacircle,orheretheinside
ofthetube,and h = length of the movement, which means pi x radius squared x height.Sincetheradiusis½oftheinsidediameter, this
equation isequivalent to= 3.1416 x (insidediameter ofthe
bent tubein mm÷2)2 xheight(equivalenttothedistancethatthesolution traveled)
= 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.

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. Thereiscurrentcontroversyastowhethertheatmosphereiswarmingduetotheburning offossilfuelsandthedestruction oftherainforests(i.e.,theGreenhouse
Effect). Howdoes photosynthesis
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. Whilethisexercisehasaddressedoxygenproduction,
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 afteryouplaced
theelodeainthetesttubeandturnedthelight 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. SetupadatatablesimilartoDataTable5:ComparisonofPhotosyntheticRate,intheLab
ReportAssistantsection.
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?

LABORATORYSUMMARY

What have you
learned from doing this laboratory?

 

ANSWER:

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