Lab Exam 2 Focus
ssume that when a chlorophyll molecule absorbs 1 photon the energy content ofthe chlorophyll increases by 3.2 x 10-19 joules. If the photon has a wavelength (λ)of 400 nm, what is the fraction of the photon's energy captured by thechlorophyll? Have your TA check your answer.photon energy
2 x 10 -16 /400 = 5 x 10 -19 Jfraction captured = 3.2 x 10 -19 J/ 5 x 10 -19 J = 0.64 or 64%
Why do you suppose a buffer was used for the isolation and functionassessment of chloroplasts?
A buffer was used to control the pH. This is necessary to maintain a constantexternal environment for the chloroplasts, which helps them survive theexperimental procedures. Also, many biological reactions are sensitive to pH;the buffer held the pH steady to eliminate changes in pH as an experimentalvariable.
Which of the following is true concerning the energy of photons?A. A 400 nm photon has more energy than a 740 nm photon.B. A 740 nm photon has more energy than a 400 nm photon.C. A 400 nm photon has the same energy as 740 nm photon, because they are both photons.
A. A 400 nm photon has more energy than a 740 nm photon.
In the oxygen production lab, what compensation was made for the heat generated by the lamps?A. A tank of water was placed in the light path to absorb heat.B. An amount was subtracted from each oxygen production rate to account for temperature effects.C. A heat-resistant strain of Chlorella was used.D. All of the above represent means that were used to compensate for the heat.E. Only A and B above were used to compensate for the heat.
A. A tank of water was placed in the light path to absorb heat.
Which of the following is/are true of the solubilities of the pigments studied in lab?A. Carotene is more soluble in ethanol than in petroleum ether.B. Chlorophyll a is more soluble in methanol than in petroleum ether.C. Chlorophyll b is more soluble in petroleum ether than in methanol.D. All of the above are true concerning the pigments studied in lab.E. Only B and C are true of the pigment solubilities.
A. Carotene is more soluble in ethanol than in petroleum ether.
When oxidized DPIP is mixed with illuminated chloroplasts what happens?A. DPIP gains electrons and loses its blue color.B. DPIP loses electrons and loses its blue color.C. DPIP loses electrons and remains transparent.D. DPIP loses electrons and gains a blue color.E. DPIP gains electrons and gains a blue color
A. DPIP gains electrons and loses its blue color
In which of the following types of population growth is the rate of growth independent of population size?A. LinearB. Unrestricted exponentialC. LogisticD. Both B and CE. None of the above
A. Linear
Which of the following is done to determine the absorption spectrum of a substance?A. Measure its absorbance over a range of different wavelengths of light.B. Plot the rate of absorbance change versus time.C. Measure its absorbance at one wavelength over time as the substance is reduced.D. Measure its absorbance at one wavelength over time as the substance is oxidized.E. Subtract the absorbance of the substance when it is reduced from the absorbance of the substance when it is oxidized.
A. Measure its absorbance over a range of different wavelengths of light.
Which of the following best represents the dependent variable in the experimentthat used the DPIP dye?A. The rate of water oxidation.B. The amount of light used to irradiate the chloroplasts.C. The pH of the buffer used in the experimentD. The amount of heat used to irradiate the chloroplasts.E. The volume of DPIP added to the blank tube.
A. The rate of water oxidation.
Which of the following characterize(s) exponential growth?A. The slope of the population size versus time graph is proportional to population size.B. The size of the population is constant.C. The number of organisms added per unit time is constant.D. A fixed number of organisms in the population may reproduce in each generation.E. All of the above characterize exponential population growth.
A. The slope of the population size versus time graph is proportional to population size.
Which of the following best explains the purpose of using a buffer in the dyereduction lab?A. To prevent changes in pH in the chloroplast preparation.B. To maintain a constant temperature in the chloroplast preparation.C. To maintain a constant amount of carbon dioxide in the chloroplastpreparation.D. To accelerate the uptake of oxygen by the chloroplast preparation.E. To prevent the loss of oxygen from the chloroplast preparation.
A. To prevent changes in pH in the chloroplast preparation
When solute potential (Ψs) increases,A. total solute concentration decreases.B. total solute concentration increases.C. total solute concentration remains the same.D. None of the above is correct.E. More information is needed.
A. total solute concentration decreases
If the solute potential (Ψs) inside of a cell is lower than the solute potential (Ψs)outside of the cell,A. water will diffuse into the cell.B. water will diffuse out of the cell.C. there will be no net diffusion of water into or out of the cell.D. solute potential (Ψs) has no effect on osmosis.E. More information is needed.
A. water will diffuse into the cell.
What is the relationship of initial population size and carrying capacity?
As is suggested in the previous question, initial population size does notaffect the carrying capacity
In the oxygen production lab, how was PFR varied?A. The PFR was varied by adjusting the offset control on the amplifier.B. The PFR was varied by adjusting the distance between the light source and the tube containing Chlorella.C. The PFR was varied by adjusting the color of the light source.D. The PFR was varied by moving the light source.E. The PFR was varied by adjusting the temperature of the light source.
B. The PFR was varied by adjusting the distance between the light source and the tube containing Chlorella.
Which of the following best represents the independent variable in the experimentthat used the DPIP dye?A. The rate of NADPH oxidation.B. The amount of chloroplast added to the reaction mixture.C. The color of light used to illuminate the chloroplasts.D. The rate of DPIP reduction.E. The volume of DPIP added to the experimental tube.
B. The amount of chloroplast added to the reaction mixture
When solute potential (Ψs) increases,A. total solute concentration remains the same.B. total solute concentration decreases.C. total solute concentration increases.D. None of the above is correct.E. More information is needed
B. total solute concentration decreases.
When solute potential (Ψs) increases,A. water concentration decreases.B. water concentration increases.C. water concentration remains the same.D. None of the above is correct.E. More information is needed.
B. water concentration increases
If the solute potential (Ψs) inside of a cell is lower than the solute potential (Ψs)outside of the cell,A. there will be no net diffusion of water into or out of the cell.B. water will diffuse into the cell.C. water will diffuse out of the cell.D. solute potential (Ψs) has no effect on osmosis.E. More information is needed
B. water will diffuse into the cell.
If the solute potential (Ψs) inside of a cell is higher than the solute potential (Ψs)outside of the cell,A. water will diffuse into the cell.B. water will diffuse out of the cell.C. there will be no net diffusion of water into or out of the cell.D. solute potential (Ψs) has no effect on osmosis.E. More information is needed.
B. water will diffuse out of the cell
If the total solute concentration inside of a cell is lower than the total soluteconcentration outside of the cell,A. water will diffuse into the cell.B. water will diffuse out of the cell.C. there will be no net diffusion of water into or out of the cell.D. solute concentration has no
B. water will diffuse out of the cell
In the oxidation of water lab that utilized the blue dye DPIP, which of the following represents a measured (dependent) variable?A. Light intensity.B. pH.C. Change in absorbance over time.D. Wavelength of light.E. Temperature.
C. Change in absorbance over time.
Which of the following do chloroplasts and sodium bisulfite hold in common? A. Sodium bisulfite may break down into DPIP and chloroplasts may produce DPIP. In either case the DPIP produced may oxidize water. B. Sodium bisulfite may break down into DPIP and chloroplasts may produce DPIP. In either case the DPIP produced may reduce water. C. Sodium bisulfite and chloroplasts may cause DPIP that is initially blue in solution to become colorless. D. Sodium bisulfite and chloroplasts may cause DPIP that is initially colorless in solution to become blue. E. Sodium bisulfite and chloroplasts both may oxidize water by adding electrons to the water.
C. Sodium bisulfite and chloroplasts may cause DPIP that is initially blue in solution to become colorless.
The reduction of DPIP by chloroplasts was coupled to which reaction below?A. The oxidation of carbon dioxide.B. The oxidation of oxygen.C. The oxidation of water.D. The oxidation of NADPox.E. The oxidation of sodium bisulfite.
C. The oxidation of water.
Without regard to the mode of population growth, which of the following best characterizes the rate of population growth?A. "N"B. "dN"C. The slope of the population size versus time graph at any point in time.D. All of the above characterizes the rate of population growth.E. None of the above characterizes the rate of population growth.
C. The slope of the population size versus time graph at any point in time.
When solute potential (Ψs) increases,A. water concentration remains the same.B. water concentration decreases.C. water concentration increases.D. None of the above is correct.E. More information is needed.
C. water concentration increases
If the total solute concentration inside of a cell is lower than the total soluteconcentration outside of the cell,A. there will be no net diffusion of water into or out of the cell.B. water will diffuse into the cell.C. water will diffuse out of the cell.D. solute concentration has no effect on osmosis.E. More information is needed.
C. water will diffuse out of the cell
If the solute potential (Ψs) inside of a cell is higher than the solute potential (Ψs)outside of the cell,A. there will be no net diffusion of water into or out of the cell.B. water will diffuse into the cell.C. water will diffuse out of the cell.D. solute potential (Ψs) has no effect on osmosis.E. More information is needed
C. water will diffuse out of the cell.
In the reaction you studied in the dye reduction laboratory, where did theelectrons that changed the DPIP come from?A. carbon dioxide.B. oxygen.C. water.D. oxidized NADPE. reduced NADP
C. water.
Chlorophyll is green; how does this relate to its absorption spectrum?Does chlorophyll absorb in the green region of the spectrum? How muchphotosynthesis would a plant carry out if it were illuminated by greenlight alone? By blue light? By red light?
Chlorophyll absorbs blue and red light pretty well, but it reflects green light, thusit appears green to us. Since green light is largely reflected, it would be of littleuse in photosynthesis. Both red and blue light ARE absorbed by chlorophylls andthus would be very useful in providing the energy required for photosynthesis.
Which of the following exercises that you performed in lab best shows that chloroplasts play a crucial role in the color change of DPIP?A. Determining the difference in the absorption spectra of chlorophylls a and bthat were removed from chloroplasts by boiling ethanol.B. Comparing the change in absorbance of an illuminated tube completely covered with aluminum foil with the change in absorbance in an identical illuminated tube that was not covered with foil.C. Checking the absorption spectra of oxidized versus reduced DPIP.D. Comparing the absorbance changes in separate tubes in which increasing amounts of chloroplasts were added.E. Determining the difference in the absorption spectra of chlorophyll a and carotenoids that were removed from chloroplasts by boiling ethanol.
D. Comparing the absorbance changes in separate tubes in which increasing amounts of chloroplasts were added.
When oxidized DPIP is mixed with illuminated chloroplasts what happens?A. DPIP loses electrons and gains a blue color.B. DPIP loses electrons and loses its blue color.C. DPIP loses electrons and remains transparent.D. DPIP gains electrons and loses its blue color.E. DPIP gains electrons and gains a blue color.
D. DPIP gains electrons and loses its blue color.
What was the purpose of using a buffer for the isolation and function assessment of chloroplasts?
D. To eliminate pH as a variable in the experiment.
DCMU is as an herbicide; it blocks the transfer of electrons out of photosystem II. (TheP680 reaction center is located in Photosystem II.) How would DCMU affect theproduction of oxygen in plants?
DCMU should lower the rate of oxygen production when compared to the rateproduced by the same PFR and no DCMU. Oxygen production will fall becauseit is dependent on anelectron-deficient P680. If P680 (part of photosystem II)can't pass electrons to the next electron carrier in the thylakoid membrane, itwon't become electron-deficient; this means that water oxidation and oxygenproduction will slow or stop. (The DCMU blockade may not be 100% effective.
Which of the following are capable of reducing DPIPox? A. Sodium bisulfite.B. Illuminated chloroplasts.C. Potassium Chloride (KCl) D. All of the above.E. Only A and B above.
E. Only A and B above.
Which of the following is/are true of the absorption spectrum of chlorophyll bas studied in lab?A. Chlorophyll b had an absorption peak at about 550 nm.B. Chlorophyll b had an absorption peak at about 640 nm.C. Chlorophyll b had an absorption peak at about at about 460 nm.D. All of the above are true of the chlorophyll b absorption spectrum.E. Only B and C are true of the absorption spectrum of chlorophyll b.
E. Only B and C are true of the absorption spectrum of chlorophyll b.
Which of the following do chloroplasts and sodium bisulfite hold in common?A. Sodium bisulfite and chloroplasts cause DPIP that is initially blue in solutionto become colorless.B. Sodium bisulfite and chloroplasts cause DPIP that is initially colorless insolution to become blue.C. Sodium bisulfite and chloroplasts reduce DPIP.D. Sodium bisulfite and chloroplasts oxidize DPIP.E. Sodium bisulfite and chloroplasts hold both A and C in common
E. Sodium bisulfite and chloroplasts hold both A and C in common
Which of the following do chloroplasts and sodium bisulfite hold in common?A. Sodium bisulfite and chloroplasts cause DPIP that is initially colorless insolution to become blue.B. Sodium bisulfite and chloroplasts cause DPIP that is initially blue in solutionto become colorless.C. Sodium bisulfite and chloroplasts oxidize DPIP.D. Sodium bisulfite and chloroplasts reduce DPIP.E. Sodium bisulfite and chloroplasts hold both B and D in common
E. Sodium bisulfite and chloroplasts hold both B and D in common
A buffer was used in the dye reduction lab. What purpose did the buffer serve?A. To maintain a constant temperature in the chloroplast preparation.B. To accelerate the uptake of oxygen by the chloroplast preparation.C. The buffer maintained a constant amount of CO2 in the chloroplast preparation.D. The buffer prevented the oxidation of sodium bisulfite by the chloroplasts.E. The buffer helped resist changes in pH in the chloroplast preparation.
E. The buffer helped resist changes in pH in the chloroplast preparation.
In the reaction you studied in the dye reduction laboratory, what was the source ofthe electrons that caused a color change in DPIP?A. oxidized NADPB. reduced NADPC. oxygen.D. carbon dioxide.E. water.
E. water.
What is the relationship between PFR and oxygen production rate in Chlorella?
Generally, the higher the PFR, the greater the oxygen production rate. Photons(essentially packets of light energy) strike photosystem II and cause it to loosean electron that is 'caught' by a nearby electron acceptor. The electron-deficient photosystem II then removes electrons from water bringing about theproduction of oxygen. The higher the PFR (photon fluence [flow] rate), thehigher the rate at which photons strike photosystem II and the higher the rateof water oxidation
Which graph best represents competition? Which graph best representspredation? How can you tell?
Graph A is most likely to be a competition in which species 2 is the loser.This conforms to the data presented in the lab. The oscillations in graph Blooks like the predator-prey situation presented in lab
What wavelengths do you think would have been least effective for drivingthe reduction of DPIP? Why?
Green wavelengths would have been least effective because they are leastwell absorbed.
Linear
Growth rate is constantand independent ofpopulation size
Logistic
Growth rate is influenced by the difference between carrying capacity and population size
Unrestricted exponential
Growth rate is proportional to population size
If the "no light control" rate was negative, what was happening to oxygen in thedark Chlorella tube?
If the "dark control" was negative, then Chlorella were consuming oxygen.
A fish farmer wishes to raise the population level by simply adding more fishto the pond. Will this work in the long term? Why or why not?
If the fish population is already at carrying capacity, then this won't work forlong. The augmented population will simply decline toward the carrying capacity and become steady at the old level. A better strategy would be to increase the carrying capacity and allow the population to expand naturally to this new, higher, level.
If DPIP spontaneously loses its blue color, what should have happened in the"No light, no heat" control
It should lose blue color and the absorbance at 10 minutes should be less thanat 0 minutes
Compare the birth rate to the death rate during the lag, log and stationaryphases of logistic growth.
Lag: birth rate > death rate, but since the population is small growth is slow.Log: birth rate > dearth rate, the population is large, so growth is rapid.Stationary: birth rate = death rate; growth is zero
Does light alone appear to be needed to drive the DPIP reduction? How can you tell?
Light alone appears to account for the great majority of the color change of DPIP because light alone causes the greatest loss of blue color
If we had been able to provide illumination of different wavelengths for the chloroplast preparation that all had equivalent energy levels, what wavelength(s) do you think would have been most effective for driving the reduction of DPIP in the reaction you studied today?
Maximum absorbance of photosynthetic pigments is in the blue and redregions of the visible spectrum. So, blue or red wavelengths should havebeen the most effective at driving the DPIP reduction reaction.
Does changing the concentration of the pigment substantially alter the position(wavelength) of the peaks?
No, the position of the peaks should not change in any significant way
For what do plants use oxygen?
The Chlorella were carrying out aerobic respiration, that is, they were using oxygen to oxidize sugars that they had made previously
Why was bisulfite added to the "blank" tubes in your experiments withchloroplast function?
The bisulfite reduced the DPIP, so the blank had everything in it that theexperimental tube had, except the blue color
hat seems to be the carrying capacity (K)in this case? How can you tell?
The carrying capacity should be the population size where the populationlevels off. Irrespective of initial size, the population seems to level off at 200.So, 200 is the carrying capacity
Where do these electrons normally end up when the full process ofphotosynthesis is occurring? How important is this for the overall process of photosynthesis?
The electrons are normally given to CO2, thereby reducing it. Reduction of CO2 to sugar is the essence of photosynthesis.
In the reaction you have been studying in this laboratory, where are theelectrons that reduce the DPIP coming from?
The electrons originate from water.
How might DCMU negatively affect the production of glucose in a plant?
The electrons that ultimately are used to help make sugar (which the plantneeds to survive) come from water that photosystem II oxidizes. If photosystemII can't deliver electrons, sugar production will stop, and eventually the plantwill die.
Which of the environmental factors below is the limiting factor? Explainyour answer.
The limiting factor will affect carrying capacity when the factor is changed.Factor "B" fits that criterion
In the experiment where the amount of chloroplasts was varied, what do yourresults show about chloroplast function?
The more chloroplasts, the faster the dye reduction, as shown by the data whengraphed. (See graphs below. You should ask your students how the datasupports the first sentence of this answer.) The direct relationship between rate of DPIP reduction and amount of chloroplasts indicates the dependence of water oxidation/dye reduction on active chloroplasts.
The absorbance spectra showed that the different pigments have peaks ofabsorbance that differ in position and height. Of the two (position orheight), which would be more useful in identifying a substance? Explain.
The positions of the peak(s) are unique for each substance, and thus can beused to identify the substance
What would be the consequences to photosynthesis be if the chlorophyllmolecule were transparent to light? What would the absorption spectrumof a colorless, transparent substance look like?
The transparent chlorophyll would absorb no light, and thus be useless inphotosynthesis. The absorption spectrum of a colorless and transparent substancewould be a flat line near zero absorbance across the visible spectrum.
What appears to be the relationship between the concentration of pigment and the height of the peaks?
There is a direct relationship: the higher the concentration of the pigment, thehigher its absorption peak.
If light and heat are required for DPIP to lose its color, how should the changein absorbance be different between the "Light and heat" control and the "Light,no heat" condition?
There should be greater loss of blue color in the "light and heat" experimentthan the "light" alone experiment
What major property of chlorophyll a, chlorophyll b and carotenoids didwe take advantage of in order to separate them from one another?
We exploited their different solubilities in the three solvents (ether, ethanol andmethanol).
Does changing the concentration of the pigment substantially alter the height(absorbance) of the peaks?
Yes. When the pigments are diluted, the amplitude of the peaks are decreased.
