Biology 110 Lab Practical 2
Look at focus question answers
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What did the buffer lock the PH at
6.8
Which of the following wavelength settings is best for having a Spec 20 detect the absorbance of light by a substance that is blue in solution?
600. Blue solutions strongly absorb light in the red region (~600nm) of the visible spectrum.
In the oxygen production lab, what compensation was made for the heat generated by the lamps?
A tank of water was placed in the light path to absorb heat.
Dependent variable in the spinach lab? (chlorophill extraction lab)
Absorbency
Water had no dissolved oxygen so what did we do?
Added a chemical to dissolve the O2. The machine would then say zero O2.
Independent variable of oxidation lab?
Amount of chloroplast added
Independent variable in production of oxygen?
Amount of light
What additive did the blank receive but the other solutions did not?
Bisulfide
What did the DCMU block-aid do?
Blocked the flow of e-
400-450 wavelength color
Blue
What color wavelength does DPIP reflect?
Blue wavelengths
Light hits which photosystem?
Both
Was chlorophyll B stored in the top layer or bottom layer in the test tube?
Bottom because it was in methanol which had a high density
How did we saturate the O2?
By stirring the H2O
Chlorophyll in ethanol?
Carotene
Which of the following is/are true of the solubilities of the pigments studied in lab?
Carotene is more soluble in ethanol than in petroleum ether.
In the oxidation of water lab that utilized the blue dye DPIP, which of the following represents a measured (dependent) variable?
Change in absorbance over time
Chlorophyll in petroleum ether?
Chlorophyll A
Chlorophyll in methanol?
Chlorophyll B
Which of the following is/are true of the absorption spectrum of chlorophyll b as studied in lab?
Chlorophyll b had an absorption peak at about 640 nm. Chlorophyll b had an absorption peak at about at about 460 nm.
Which of the following exercises that you performed in lab best shows that chloroplasts play a crucial role in the color change of DPIP?
Comparing the absorbance changes in separate tubes in which increasing amounts of chloroplasts were added. Showing that increasing amounts of chloroplasts increase the rate of DPIP reduction provides evidence that chloroplasts are the active ingredient in this experiment.
What did calibration tell us?
Conversion factor
Rate of reaction (y) vs. mL of chloroplast (x) is what kind of relationship?
Direct relationship
What is reduction?
Gain of electrons
500-550 wavelength color
Green
Chloroplast has everything to make the reaction causing an increase in what?
H2O oxidation
What kind of density did methanol have?
High density
What did bisulfide do in the blank?
It changed the color to clear
O2 production (y) vs. PFR (x) is what kind of relationship?
It is a direct relationship
If DPIP is oxidized what happens?
It stays a blue color
If DPIP is reduced what happens?
It turns to a clear color
Which factor (light or heat) played a larger role in driving the reaction?
Light
What played a factor in absorbance?
Light and heat
What type of driven reaction is photosynthesis?
Light driven reaction
What is oxidation?
Loss of electrons
What kind of density did petroleum ether have?
Low density
Which of the following is done to determine the absorption spectrum of a substance?
Measure its absorbance over a range of different wavelengths of light.
More excitement of e- means what?
More energy to do work (making O2)
More photons that hit photosystem I means what?
More excitement of e-
What does water split into?
O2 and H+
Is NADP+ reduced or oxidized?
Oxidized
3 Pigments?
Petroleum ether, ethanol, & methanol
Dependent variable in production of oxygen?
Production of O2
Dependent variable for oxidation lab?
Rate at which water was oxidized or the reduction of DPIP
700-750 wavelength color
Red
Which of the following do chloroplasts and sodium bisulfite hold in common?
Sodium bisulfite and chloroplasts may cause DPIP that is initially blue in solution to become colorless.
Which of the following are capable of reducing DPIPox?
Sodium bisulfite and illuminated chloroplast
In the oxygen production lab, how was PFR varied?
The PFR was varied by adjusting the distance between the light source and the tube containing Chlorella.
The absorption spectrum of carotenes as determined in lab sometimes showed an absorption peak in the red region of the spectrum. However, the absorption spectrum of carotenes shown in the textbook did not show such a peak. What caused this difference?
The carotenes extracted in our lab were contaminated with chlorophyll; the carotenes used in the textbook were not contaminated with chlorophyll
The reduction of DPIP by chloroplasts was coupled to which reaction below?
The oxidation of water. When water is oxidized in photosynthesis it looses electrons. Those electrons are available to reduce DPIP.
Note the electron carriers in the thylakoid membrane above. When chloroplasts are exposed to light, an electron acceptor, DPIP, is reduced by electrons from carrier #3. When a particular plant poison is added to illuminated chloroplasts, DPIP is not reduced. Which of the following explains that observation?
The poison blocks the oxidation of water. The poison blocks the transfer of electrons from #1 to #2. The poison blocks the transfer of electrons from #2 to #3.
What was the purpose of using a buffer for the isolation and function assessment of chloroplasts?
To eliminate pH as a variable in the experiment. The buffer maintained constant pH.
Was chlorophyll A stored in the top layer or bottom layer in the test tube?
Top because it was in petroleum ether which had a low density
Independent variable in the spinach lab? (chlorophill extraction lab)
Wavelength, light
What do chorophylls absorb best
blue light
What is the relationship between energy and wavelength
inverse
What does chlorophyyll a absorb best
red
Where do the elctrongs for DPIP come from
water
what did sodium sulfate do
zero oxygen concentration
