Chlorophyll

In plants, the process of photosynthesis takes place in the mesophyll of the leaves, inside the chloroplasts. Chloroplasts contain disc-shaped structures called thylakoids, which contain the pigment chlorophyll. Chlorophyll absorbs certain portions of the visible spectrum and captures energy from sunlight.

Plant pigments are classified into four main categories: chlorophylls, anthocyanins, carotenoids, and betalains.

Spinach is an excellent source of carotenoids. Carotenoids are made up of two major divisions, the xanthophylls and the carotenes. In spinach, the main xanthophylls are lutein, cryptoxanthin and zeaxanthin.

Xanthophyll contains oxygen and does not travel quite as far with the solvent because it is less soluble the beta carotene and forms hydrogen bonds with the paper. Chlorophylls are bound more tightly to the paper than the other two, so they travel the shortest distance.

carotene

Carotene moves the farthest because it is the most nonpolar of the pigments and it is attracted more strongly to the acetone-ligroin mixture (mobile phase) than to the paper. This stronger, nonbonded interaction with the mobile phase indicates that carotene is the most nonpolar pigment found in spinach chloroplasts.

Spinach leaves, which the students will use in this assignment this quarter, contain chlorophyll a, chlorophyll b and β-carotene as major pigments as well as smaller amounts of other pigments such as xanthophylls.

As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green.

Chlorophyll a absorbs violet and orange light the most. Chlorophyll b absorbs mostly blue and yellow light. They both also absorb light of other wavelengths with less intensity.