The photosynthetic pigment is used to absorb light during the process of photosynthesis. There are five pigments usually found in spinach leaves: Carotene (yellow), Phaeophytin (yellow-grey), Xanthophyll (yellow-brown), Chlorophyll a (blue-green), Chlorophyll b(green). Photosynthetic pigment is located in the chloroplast of the leaf.
The function of chlorophyll a and chlorophyll b is to trap red and blue violet light when they carry out photosynthesis, chlorophyll a occurs in green plants while chlorophyll b occurs in green algae.Carotene and Xanthophyll are carotenoid where it can protect the human eye from being harm by light and act as antioxidant thus prevent cardiovascular disease. Objective
To determine the content of photosynthetic pigment in spinach leaves. Procedure :
1. Spinach leaves is plucked and cut into smaller pieces before placing into the mortar. 2. Suitable amount to Acetone is added into the mortar and the leaves are grinned using the pestle until there is pigment solution from the spinach. 3. The spinach is filtered using a muslin cloth into a smaller beaker and the residue is being squeezed until there is sufficient amount of greenish solution is in the beaker. 4. A straight line is drawn 1cm away with a pencil from the edge on a strip of filter paper and a centre spot is marked. 5.
The solution is dropped on the dotted spot by using a dropper. The droplet is left to dry and this step is repeated until a concentrated greenish dot is formed on the dotted spot. 6. The filter paper strip is placed and pinned vertically into the test tube. Acetone solution is filled in the test tube until below the line of the filter paper strip.
The test tube is sealed with a stopper and under the boiling chamber. 7. When the solvent almost reached the end of the filter paper strip, the filter paper strip is taken out to observe on the chlorophyll pigment separation and a pencil line is ruled to mark the solvent front. The filter paper strip is then dried. 8. Pigments are then identified by the colours and the Rfvalues obtained.
By comparing the Rf value from Table 1 and Table 2, we can find that there is Carotene, Phaeophytin, Xanythophyll, Chlorophyll a and Chlorophyll b present in the spinach leaves. But the Rf value of Chlorophyll b is not similar with the Rf that was calculated. It may be because of the calculations of the distance was done wrongly and therefore affect the Rf value of the Chlorophyll b.
The molecules of carotene are the smallest and they are unsaturated hydrocarbon, thus the solubility of the molecule in organic solvent is the highest, the molecules move the fastest. Phaeophytin has two hydroxyl, it increases the polarity in organic solvent, it is less soluble compare with carotene. Phaeophytin molecule is bigger than carotene molecule and follow by xanthophyll molecule. The size of molecule of chlorophyll is the biggest and it has a hydrophilic ‘head’, thus the diffusion of the molecule is the slowest.
Yet, chlorophyll a diffuse faster than chlorophyll b. The Rf value of pigment we found is not same as the given sample. The concentration of pigment solution is not condense thus do not give accurate result. There might be some contaminate substance on the paper while we carry out the filter paper.
1. PHOTOSYNTHETIC PIGMENTS.(2004).Retrieved November 2, 2011 from http://biology.wsc.ma.edu/biology/courses/concepts/labs/pigments/ 2. Rowan K.S.(1989).PHOTOSYNTHETIC PIGMENTS OF ALGAE. Cambridge University Press. http://books.google.com.my/books?hl=en&lr=&id=aZNOAAAAIAAJ&oi=fnd&pg=PA1&dq=p