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Photosynthesis/Table 1. Metric System: Length Measurement Units

Photosynthesis/Table 1. Metric System: Length Measurement Units

Daniel Kevins

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Table 1.Metric System: Length Measurement Units

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Quantity	Numerical Value	English Equivalent	Converting to Metric
kilometer (km)	1,000 m	1 km = 0.62 mile	1 mile = 1.609 km
meter (m)	100 cm	1 m = 3.28 feet = 1.09 yard	1 yard = 0.914 m 1 foot = .305 m
centimeter (cm)	0.01 m	1cm = 0.394 inch	1 foot = 30.5 cm
millimeter (mm)	0.001 m	1 mm = 0.039 inch	1 inch = 2.54 cm
micrometer (1 µm), also called a “micron (µ)”	0.000001 m
nanometer (nm), also called a “millimicron(mµ)”	0.000000001 m
angstrom (å)	0.0000000001 m

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*Note: In other sources, you will sometimes see another unit, the nanometer (nm), used to measure wavelength. Each nanometer is equal to ten angstroms: for example, 7000 Å=700 nm. Although both the angstrom and the nanometer are used to measure wavelength, the nanometer is currently the more frequently used unit.

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Question 1. Using Table 1, complete the following:

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There are _________ centimeters (cm) in a meter (m).

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There are _________ millimeters (mm) in a meter (m).

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There are _________ micrometers (microns or µm) in a meter (m).

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There are _________ nanometers (nm) in a meter (m).

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There are _________ Angstroms (Å) in a meter (m).

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Question 2. Look at the chart on the wall. It gives nanometer (nm), rather than angstroms as the until of wavelength. Since one nanometer is equal to 10 angstroms, 3500 (Å) = 350 nm. Write down the wavelengths in nanometers, using this simple conversion. Nanometer is currently the more frequently used unit.

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In the table below, arrange the six visible light colors in a sequence starting with the one with the shortest wavelength and ending with the color with the longest wavelength. Also, indicate the approximate wavelengths of the colors. You will fill in the last column using the information in the next question.

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Wavelength	Observed Color	Approximate Range of Wavelengths (nm)	Relative Energy
Shortest	1.
	2.
	3.
	4.
	5.
Longest	6.

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Question 3. It is known that shorter wavelength light possesses more energy than longer wavelengths. Indicate in the table in, Question 2, which color has the highest energy and which color has the lowest energy.

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Question 4. Describe the color change when you shine the light on the pigment extract:

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Question 5. In the space below, sketch your paper chromatogram using colored pencils. Then label the pigment bands with their respective pigments.

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Question 6. Based on how far it migrated, which pigment must have the greatest affinity for the chromatography solvent? Give the name of the pigment.

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Which must have the least affinity? Give the name of the pigment.

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Determining the Absorption Spectrum of the Leaf Pigments

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As light strikes a pigment, certain wavelengths will be reflected or transmitted, and some will be absorbed. Figure 3 shows a theoretical absorption spectrum.

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Figure 3. Theoretical Absorption Spectrums

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of Two Plant Pigments

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Question 7. Generally speaking, which wavelength ranges and their corresponding colors are most strongly absorbed by the pigments in Figure 3? (See your answer from Question 2.)

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Pigment:	Ranges:	Colors:
Chlorophyll a
Chlorophyll a
Chlorophyll b
Chlorophyll b

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Question 8. Which wavelength ranges and corresponding colors are least absorbed? (See your answer from Question 2.)

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Pigment	Ranges:	Colors:
Chlorophyll a
Chlorophyll b

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Table 1.

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Percent Transmittance at Wavelengths 400 nm – 700 nm

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400	425	450	475	500	525	550	575	600	625	650	675	700

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Subtract the above values from 100%, since % T + % A = 100%. Write the results in the Table 2 blanks below:

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Table 2.

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Percent Absorption at Wavelengths 400 nm – 700 nm

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400	425	450	475	500	525	550	575	600	625	650	675	700

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Using the data from Table 2, plot your team’s leaf pigment absorption spectrum curve on Figure 10.

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80%
60%
40%
20%
0%
	400	500	600	700
	Wavelength (nm)

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Figure 10. Observed Absorption Spectrum for Grass Leaf Pigments

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Question 9. On the graph above, at what two wavelength ranges do you see the “peaks” of light absorption? Label colors of light that are found in these two ranges, based on your answer from Question 2.

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Question 10.

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In what general range of wavelengths is absorption low?

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What colors of light are found in this range?

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Question 11.

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What happens to the light that is not absorbed in a solution? How does this relate to the fact that leaves appear green?

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What happens to the light that is not absorbed in the solutions we used in the spectrophotometers?

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Question 12. Although a plant’s leaf is its primary organ for photosynthesis, not all the cells in a leaf are photosynthetic.

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Observe the epidermal peel diagram on the bottom left side of Figure 5, as well as the model. Do all of the cells in the epidermal peel have chloroplasts? ____________ (Hint: Look for the cells that have chloroplasts in them! They appear as small, dark dots or ovals inside the cells drawn in Figure 5.)

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What is the name of the cells in the surface of the leaf that have chloroplasts? ___________________________________

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Now observe the diagram of the leaf cross section on the bottom right of Figure 5, as well as the model. Which cells have chloroplasts in this part of the leaf? ____________________________________

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Question 13. Observe the openings in the leaf’s epidermis in Figure 5 and on the model. What are they called? __________________________ If plants take in gaseous carbon dioxide (CO2) from the air and release oxygen (O2), how do the gases enter and leave the leaf?

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Question 14. Observe Figure 5 on the bottom right. Is the cellular material inside the leaf arranged so that the leaf is a solid mass, or are there spaces left inside?

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Question 15. If we could somehow remove the gases from a leaf without killing all the cells and then expose that leaf to sunlight, water and CO₂ for a given amount of time, what gas would be produced that would refill the spaces within the leaf? ________________

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Question 16. Write the summary equation for photosynthesis:

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Question 17. How does your answer to Question 15 relate to your answer in Question 16?

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Let’s identify the components of the hypothesis.

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Question 18. What is the independent variable? (The one you will let vary in the different “treatment levels”)?

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Question 19. Name a dependent variable (or variables) (the variable(s) that you will measure to see if the Independent variable has an effect).

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Question 20. Now that you have the independent and dependent variables, create a hypothesis.

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Question 21. List the most important “controlled variables” (the ones that might wrongly affect your results if they are not “controlled.” These are also called confounding variables in the Understanding Experimental Design simulation).

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Question 22. Observe the leaf discs before vacuuming them: Are they now floating, or are they on the bottom of the flask?

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Table 3. Leaf Disc Data

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Distance	Team		Time (sec)		Team	All Teams
	Number	Disc 1	Disc 2	Disc 3	Averages	Average
15 cm	1					X
	2	X	X	X	X	X
	3	X	X	X	X	X
	4	X	X	X	X	X
60 cm	1					X
	2	X	X	X	X	X
	3	X	X	X	X	X
	4	X	X	X	X	X

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Question 23. According to your team’s data, would you accept or reject your hypothesis regarding the effect of light intensity on photosynthetic rate? (Question 20)

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Describe exactly how your data lead to the above conclusion.

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Question 24. You also have data from all teams in your class. According to the class average from Table 3, would you accept or reject your hypothesis?

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Describe exactly how the data lead to the above conclusion.

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Question 25. If the class average data causes you to reject your hypothesis, present a new one in the space below.

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Question 26. Perhaps your data were inconclusive or even contrary to the class average. List some sources of experimental error which could cause a team’s data to not fit the class average pattern:

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Question 27. Those who designed this laboratory exercise have tried to use certain procedures in the performance of the experiment to minimize experimental error or “control the variables.” Identify some of those procedures:

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Question 28. Why have we used uniform discs and not whole leaves?

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Question 29. Examine the formula for sodium bicarbonate. What ingredient, essential for photosynthesis, does it provide to the leaf discs?

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Daniel Kevins

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