3. Questions
Activity 4
Background questions
Where (i.e. in what organelles) would you find chlorophyll?
Are these organelles in the leaves as well as the stems? __________ How can you tell? ________________________________________________________________________________
Results
If you have a strip, tape it to this page and label the pigment layers. Otherwise draw the strip and label the pigment layers.
Activity 5
From examination of the absorption spectra, Figure 4, answer the following questions.
1. Chlorophyll "A" absorbs which colors best? _______________and______________
2. Chlorophyll "B" absorbs which colors best? _______________and______________
3. Carotenoids absorb which colors best? ____________________and____________
Now that you have your pigments separated, an illustration of the absorption spectra of chloroplast pigments and the action spectrum of photosynthesis, you can begin to relate everything to your Elodea plants.
Which pigments did you discover were in the Elodea?
What do the pigments present in Elodea suggest about the colors of light which would be absorbed by Elodea?
If you move the light source, used in Activity 3, to a distance of twice the original distance, what do you believe would happen to the photosynthesis rate? (Increase, decrease or remain the same.) Why?
Specifically, how does chlorophyll direct and stimulate photosynthesis?
This Is The Background Info!:
- Attachment 1
- Attachment 2
- Attachment 3
- Attachment 4
- Attachment 5
- Attachment 6
- Attachment 7
Cork stopper for the jarPaintbrush, fine-tippedPaper clipPliers, pointed nosePaper ChromatographyOnce the solution of pigments has been obtained you will determine what supportpigments, in addition to chlorophyll, are in the cells of Elodea. This will be achieved usingpaper chromatography.Background questionsAnswer the background questions under Activity 4 in your laboratory report.Procedure1. Gather up a small handful of Elodea from the beaker on the bench in the laboratory.Grind it up with some sand in a mortar with some methanol. Pour your mix into a smallbeaker and heat in a pre-heated water bath for 10 minutes. *Note: 20 ml of methanolshould be sufficient.Obtain the large test tube, cork, pin, paper clip and chromatography paper. Handle paperby edges only to avoid getting oils from your fingers on the paper, which would interferewith the separation of pigments. Cut small notches about 2 cm from the end on one sideof the paper, and cut off the corners from this end.Insert the pin in the cork, and bend the pin 90 degrees to form a hook. Attach the paperclip to the uncut end of the paper and suspend in the test tube to check the length. Thepaper should end just above the bottom of the tube. Adjust the length of paper or paperclip accordingly. Remove the paper clip for the next step.Use a small paintbrush to apply six layers of chlorophyll extract to the chromatographypaper, in a line or dot between the notches cut into the end of the paper strip,allowing the extract to dry between successive layers.5. Under the fume hood, pour developing solvent into the test tube, about 1 cm deep. Thelevel should be high enough to touch the bottom of the chromatography paper, but not highenough to touch the pigment spot on the paper.6. Take the tube back to your bench and insert the cork with suspended paper. Whilekeeping the tube upright, observe the solvent, with dissolved pigments, migrating up thepaper.7.When the solvent front has reached 2 cm below the top of the paper, remove the cork andpaper and place on a paper towel to dry. Return developing solvent to waste solvent jarunder the fume hood.8.Examine your chromatographyour strip, carefully to see all of the pigments. Somemay be very faint or closely-spaced. Bright yellow at the top is carotene (a carotenoid),blue-green is chlorophyll a, and yellow-green is chlorophyll b.
