6.5: Pigments and Photosynthesis
- Page ID
- 133653
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Within the chloroplasts are photosynthetic pigments. These pigments, such as chlorophyll a and chlorophyll b, help capture light energy for the plant. However, these pigments cannot just capture any wavelength of light. Chlorophylls are limited in which light wavelengths they are able to absorb. Any wavelength of light they cannot absorb is reflected. This is why plants appear green, as green wavelengths (500-600 nm) are reflected, while blue wavelengths (425-500 nm) and red wavelengths (600-700 nm) are readily absorbed.
Chlorophyll_ab_spectra2.PNG: Daniele Pugliesi derivative work: M0tty, CC BY-SA 3.0, via Wikimedia Commons
Chlorophylls are not the only pigments found in plants, however. Other pigments such as carotenoids (which appear yellow and orange) and anthocyanins (which take on shades of red and blue) may also be found alongside the chlorophylls. For this final exercise, we will discover which pigments are found within a spinach leaf.
Hypothesis: Based on the above information, which pigment(s) do you think you will see in a spinach leaf?
Materials:
- 2-3 fresh spinach leaves
- A pencil, paperclip, and coin
- A 10 cm length of chromatography paper
- Chromatography solvent or acetone
- A small beaker
- A metric ruler
Procedure:
- Fold the chromatography paper in half lengthwise.
- Measure 2 cm away from one edge and draw a point or line at the 2 cm measurement.
- Place a spinach leaf on the point or line and use the coin to press the leaf into the paper.
- Continue pressing, using fresh parts of the leaves until a solid line of spinach extract has been pressed into the paper. (See example image below.)
- Obtain 10 mL of chromatography solvent (or acetone) from the instructor in the beaker.
- Place the chromatography paper in the beaker with the spinach end closest to the solvent and the other end facing up. (See example image below.)
- Use the paperclip to hold the paper to the beaker.
- Let sit for 45 minutes. Check periodically to ensure that the solvent does not fully evaporate. If the solvent runs low, obtain more from your instructor.
- After 45 minutes, record and draw your results.
"Paper Chromatography Setup" by Karen Marks, Reedley College is licensed under CC BY 4.0
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Pigment(s) Present (include color) |
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Drawing of Chromatography Paper |
How do your results compare to your hypothesis?
Were there any pigments present that surprised you?
In the fall, leaves lose their green color and instead appear in shades of yellow, orange, and red. Based on your knowledge of plant pigments, which pigments disappeared from the leaves? Which ones are likely still present?