BSC 2011L BSC 2011L PhotosynthesisPhotosynthesis

Today’s Lab...1.) Turn in library worksheet. 2.) Quiz # 1 3.) Photosynthesis Lab4.) Due next wk

-- abstract (15 pts)-- graphs (10 pts)

5.) Quiz #2 next week, Ann teaches

Michelle C 4Kristen H. 0.5Allison H. 1Alex H. 0.5Michelle H. 5Dallas J. 2Sheena M. 2

Michael D. 2David E. 2.5Dahlia K. 3.5Brian M. 2.5Joseph M. 1Anna P. 3

3. What is the difference between a reflex and a reaction? DRAW AND LABEL A SIMPLE DIAGRAM to explain your answer.

4. Close your right eye, look at the cross with your left eye. The circle will disappear.EXPLAIN WHAT IS HAPPENING

5. In this lab we will be measuring 2 factors that affect the rate of photosynthesis they are

A) temperature and lightB) chlorophyll A and chlorophyll BC) wavelength and intensityD) DCPIP and NADPHE) glucose and sucrose

1. What is indicated by the arrow, and what is its function?

2. List two structures of the eye are directly involved in accommodation.

QUIZ 1

Quiz Bank: NOTE the number of the question you wish to substitute - DO NOT answer that question!

Cyanobacteria

CYANOBACTERIA

2.7 billion years old

An overview of photosynthesisAn overview of photosynthesis

LLeaves are structured eaves are structured to facilitate photosynthesisto facilitate photosynthesis

A.A. EpidermisEpidermis with with stomatastomata..

B.B. Spongy mesophyllSpongy mesophyll - gas - gas exchange.exchange.

C.C. Pallisade mesophyllPallisade mesophyll - - chloroplasts.chloroplasts.

chlorophyll is the chlorophyll is the pigmentpigment within within chloroplastschloroplasts

LLeaves are structured eaves are structured to facilitate photosynthesisto facilitate photosynthesis

The site of photosynthesis in a plantThe site of photosynthesis in a plant

Chloroplast Chloroplast structurestructure

A.A. 2 membranes (2 membranes (outerouter and and innerinner).).B.B. StromaStroma - fluid filled interior. - fluid filled interior.C.C. ThylakoidThylakoid membranous sacs. membranous sacs.D.D. ThylakoidThylakoid sacs layered as grana. sacs layered as grana.E.E. ChlorophyllChlorophyll in thylakoid membranes. in thylakoid membranes.F.F. Thylakoids function in converting light energy to Thylakoids function in converting light energy to

chemical energy (= light-dependent reaction).chemical energy (= light-dependent reaction).

G.G.COCO22 conversion to sugars occurs in the stroma (= conversion to sugars occurs in the stroma (= carbon-assimilation reaction) = carbon-assimilation reaction) = Calvin cycleCalvin cycle..

The Photosynthetic ReactionThe Photosynthetic Reaction

A. What happens:A. What happens:1. Plants capture light energy.1. Plants capture light energy.2. Combine carbons from CO2. Combine carbons from CO22 into CHOs. into CHOs.3. Incidentally release O3. Incidentally release O22..

B.B. 66COCO22 + + 1212HH22OO + light + light 11CC66HH1212OO66 + + 66OO22 + + 66HH22OO

C. This is a C. This is a reversereverse of of cellular respiration.cellular respiration.

Tracking atoms through photosynthesisTracking atoms through photosynthesis

Carbon dioxide Water

Glucose Water Oxygen

Interaction of light with chloroplastsInteraction of light with chloroplasts

Light DEPENDENT reactions Photosystem I & Photosystem II

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.

Light-dependent ReactionLight-dependent Reaction

A.A. S Solar energy ---> chemical energy.olar energy ---> chemical energy.

B.B. Light absorbed by chlorophyll.Light absorbed by chlorophyll.

C. C. Drives transfer of eDrives transfer of e-- from split water to NADP from split water to NADP++, , temporarily stores etemporarily stores e-- as NADPH + H as NADPH + H+.+.

D. D. OO2 2 is released.is released.

E.E. Generates ATP by adding phosphate to ADP = Generates ATP by adding phosphate to ADP = photophosphorylation.photophosphorylation.

Results ofResults ofLight-dependent reactionLight-dependent reaction

1.1. NADPHNADPH - source of energized electrons. - source of energized electrons.

2.2. ATPATP - energy source for cellular activities. - energy source for cellular activities.

3.3. ReleaseRelease of O of O22..

Light independent reactionLight independent reactionCarbon Assimilation ReactionCarbon Assimilation Reaction

A. A. Incorporates Incorporates COCO22 from air into organic from air into organic material = material = carbon fixationcarbon fixation..

B. B. Fixed carbonFixed carbon is is reducedreduced to to carbohydratecarbohydrate by addition of by addition of ee--..

REQUIRES ENERGY and electronsREQUIRES ENERGY and electronsC. C. NADPHNADPH offers offers electronselectrons..D. D. ATPATP offers offers energyenergy..E. E. Carbon Assimilation reaction results in Carbon Assimilation reaction results in formation formation

of sugarsof sugars..

Light independent reaction – making the donuts!

Light dependent reaction – capturing energy from the sun

?

SUNLIGHT H O Light-dependent reactions O (thylakoids) ADP, NADP ATP, NADPH CO + H O Light-independent reactions Glucose (stroma)

2 2

2 2

+

LIGHT REACTION

DARK REACTION

*note: “dark reactions” = “light independent” reaction = Calvin cycle = carbon fixation happens in dark and light

What are we doing in this experiment?What are we doing in this experiment?

A. We use an artificial electron acceptor A. We use an artificial electron acceptor (DCPIP) in place of NADP+.(DCPIP) in place of NADP+.

...oxidized DCPIP is ...oxidized DCPIP is blueblue

...reduced DCPIP is ...reduced DCPIP is colorlesscolorless

B. So...we can use the spectrophotometers to B. So...we can use the spectrophotometers to measure the decrease in oxidized DCPIP.measure the decrease in oxidized DCPIP.

DCPIP used in place of NADP+.DCPIP used in place of NADP+.

We will look at the effects of two We will look at the effects of two variables on photosynthetic rate:variables on photosynthetic rate:

1.) Light intensity1.) Light intensity

uEinstein /m2

2. 2. WavelengthWavelength

(nm)(nm)

“What is an Einstein?”

uEinstein /m2 /min is a common measure of light irradiance or light “intensity”

1 "Einstein" = 1 mole of photons1 mole = 6.02 x1023 particles of a

substance, such as atoms, molecules or photons

In this case the units are "microEinstein" 1 uEinstein = 1 millionth of a mole of photons1 uEinstein = 6.02 x 1017 photons

The electromagnetic spectrumThe electromagnetic spectrum

Photosynthetic wavelengths

LET’S HYPOTHESIZE...

I.) Wavelength

II.) Light intensity

SpectrophotometersSpectrophotometers

A. A. Should be set at 600 nm.Should be set at 600 nm.

You will prepare You will prepare three cuvettes...three cuvettes...

Why?Why?

* an * an experimentalexperimental* a * a controlcontrol* a * a blankblank

Blanks for these trials will include everything Blanks for these trials will include everything but the DCPIP.but the DCPIP.

For the wavelength experiments only, For the wavelength experiments only, add 0.5 ml of thylakoidsadd 0.5 ml of thylakoids. .

Reduce the amount of water added. Reduce the amount of water added.

EXPERIMENTAL CONTROL BLANK DCPIP 2.5 ml 2.5 ml Water 2.0 ml 2.0 ml 4.5 ml PO4 buffer 2.0 ml 2.0 ml 2.0 ml chloroplasts 0.2 ml* 0.2 ml* 0.2 ml* ------- ------- -------- 6.7 ml 6.7 ml 6.7 ml

* DO NOT add chloroplasts until ready to begin experiments.

0.5 ml 0.5 ml 0.5 ml

1.7 ml 4.2 ml1.7 ml

wavelength wavelengthwavelength

What to put in cuvettes...

Make the cuvettesMake the cuvettes

A.A. Each group will need 5 ml DCPIP, 8.5 ml water Each group will need 5 ml DCPIP, 8.5 ml water and 6 ml buffer.and 6 ml buffer.

B.B. Mix the blank first.Mix the blank first.

C.C. Then Mix DCPIP/HThen Mix DCPIP/H22O/buffer for the experimental O/buffer for the experimental and control cuvettes.and control cuvettes.

D.D. When ready to begin, mix the chloroplasts wellWhen ready to begin, mix the chloroplasts wellE.E. Turn off the lights before adding 0.2 ml of Turn off the lights before adding 0.2 ml of

chloroplasts to each cuvette and mixing.chloroplasts to each cuvette and mixing.F.F. TAKE TIME ZERO READING IMMEDIATELY.TAKE TIME ZERO READING IMMEDIATELY.

Thylakoid suspensions are Thylakoid suspensions are exposed for two (2) minutes, exposed for two (2) minutes,

then light can be shut off while then light can be shut off while absorbencies are measured.absorbencies are measured.

Wavelength experimentWavelength experiment

A.A. You will test photosynthetic rate in four different You will test photosynthetic rate in four different wavelengths of light (blue, green, red, and far red). wavelengths of light (blue, green, red, and far red).

B.B. The distances between the light sources and filters The distances between the light sources and filters have been calibrated so that the same light have been calibrated so that the same light intensity exists beneath each filter.intensity exists beneath each filter.

C.C. DO NOT ADJUST THE LIGHTS. They are set at a DO NOT ADJUST THE LIGHTS. They are set at a constant number of microeinsteins/mconstant number of microeinsteins/m22/sec; 1 /sec; 1 einstein = 1 mole of photons.einstein = 1 mole of photons.

D.D. Keep water in the glass casserole dishesKeep water in the glass casserole dishes. . If liquid in casserole dishes in low, add distilled water.If liquid in casserole dishes in low, add distilled water.

Light intensity experimentLight intensity experiment

A. A. You will analyze the effects of light You will analyze the effects of light intensity on photosynthetic rate.intensity on photosynthetic rate.

B. B. Distance from the light source and light Distance from the light source and light intensity will be recorded on the counter intensity will be recorded on the counter underneath the light tunnel.underneath the light tunnel.

4 figures with captions required2 Raw data graphs (one for wavelength, one for intensity)

Absorbance vs. time

fit straight best-fit line

slope of line = reaction rate

subtract reaction rate of control (ie. Light pollution) from reaction rate of experimental cuvette to get reaction rate of only the wavelength/intensity tested

The Reaction Rate ve. Intensity graph -- The Reaction Rate ve. Intensity graph -- The amount of The amount of energy falls off as the square of the distance from energy falls off as the square of the distance from the source (= the inverse square law).the source (= the inverse square law).

A.A. The The Reaction RateReaction Rate vs. vs. wavelengthwavelength graph might mimic (roughly) the graph might mimic (roughly) the absorption spectrum for absorption spectrum for chlorophylls chlorophylls aa and and bb..

2 more graphs1. reaction rate vs wavelength 2. reaction rate vs. intensity

A A Reaction RateReaction Rate versus versus distancedistance graph would be an exponential curve.graph would be an exponential curve.

A A Reaction RateReaction Rate versus versus intensityintensity should be linear.should be linear.

FiguresFigures

A. These take some time to get right.A. These take some time to get right.

B. B. Pay close attention to format.Pay close attention to format.

C. C. There will need four for this assignmentThere will need four for this assignment

1.1. 2 raw data figures (absorbance vs. time)2 raw data figures (absorbance vs. time)

2.2. 2 reaction rate figures (reaction rate vs. 2 reaction rate figures (reaction rate vs. parameters, I.e., wavelength and intensity)parameters, I.e., wavelength and intensity)

Example of a proper graph...

* Ensure that axes are properly labeled, with units

specified, even if there are no units (AU=arbitraty units) * Do not connect the points on the graph with lines; draw a best-fit line through the data set. * The independent variable (the variable you manipulate) should always be on the X-axis and the dependent variable (the read out from the instrument) should be on the Y-axis. * Include a descriptive title that explains what kind of plot it is, the technique that was used, which substance was measured, and what instrument was used to measure it. * IMPORTANT: Titles should not include (or be) "Plot of...", "Graph of...", or "...over a range of data points." - Be concise, but complete. * Do not plot too many data sets on a single graph - make multiple graphs if required.

WRITE A DETAILED CAPTION FOR EACH GRAPHsee -- see -- http://abacus.bates.edu/~ganderso/biology/resources/writing/HTWtablefigs.html

* Use * Use different colorsdifferent colors or symbols for or symbols for each variable.each variable.

* A * A best fit linebest fit line for each set of data. for each set of data.* Use this line to calculate reaction rate * Use this line to calculate reaction rate

values.values.