Photosynthesis: Chromatography Paper Results Of Spinach Leaves

Introduction:

Photosynthesis is a process where plants and other organisms transform the radiant energy of sunlight into the chemical energy of high-energy compounds by converting carbon dioxide and water into the simple sugar glucose. However, this process is not as simple as it seems. Photosynthesis occurs in two stages. The first stage is light dependent reactions and the second stage is light independent reactions. Each plant also has its own way to go through photosynthesis which is what makes plants different from one another. One important aspect that gives plants its uniqueness are pigments. Pigments are the compound that absorbs the certain wavelengths from the sun, to pass to other compounds so that light-dependent reactions can occur.

Part 2: Spinach Leaf Chlorophyll Extraction

If the chlorophyll extract is held directly under light, the chlorophyll molecules will get excited and move from their ground energy state to a higher energy state and re-emit the light causing fluorescence of light to be seen.

Procedure:

Refer to lab handout

Observations:

Part 1:

Chromatography Paper Results of Spinach leaf

Pigment Colour Distance travelled by pigment (cm) Distance travelled by solvent (cm) Rf (reference flow value) Name of Pigment

Green 14.5cm 14cm 1.04 Chlorophyll a

Green 14cm 14cm 1.00 Chlorophyll b

Refer to next page for diagram of chromatography paper.

Part 2:

When the leaf is held in the light, you can see a lighter green colour. When the chlorophyll extract is held in the light the colour red is seen.

Discussion Questions:

1) A pigment is defined as a compound that absorbs specific wavelengths of light that is visible while reflecting others. In plant leaves, pigments that in embedded in the thylakoid membrane will absorb light energy from the sun which initiates light dependent

Chlorophyll a and chlorophyll b were the two pigments that were present in spinach leaves. This justified the hypothesis stated. The solvent travelled a distance of 14cm on the chromatography paper. The distance travelled by pigment chlorophyll a was 14.5cm with a Rf value of 1.04 and chlorophyll b reached 14cm with a Rf value of 1.00. Since chlorophyll a was present in the spinach leaf, it can be concluded that spinach leaves absorb red and blue lights while reflecting yellow and green which is why humans see the colour green. It is also Chlorophyll b on the other hand, is an accessory pigment however it also absorbs more red and blue wavelengths and also reflects a green colour. The second hypothesis for the second part to this lab was also proven correct. When the chlorophyll pigment in the test tube was held directly under the light, a florescence of colour was seen. In this experiment a colour of purple/pink was seen, however chlorophyll extract should have shown the colour of red when held directly under light. This means that this lab must have had experimental error. Even though a fluorescence of light was seen when the chlorophyll molecule was struck by light, if all chlorophyll molecules re-emits florescence when struck by light, photosynthesis will not occur as chlorophyll is lost. Instead, when a chlorophyll molecule absorbs