Photosyntesis Essay, Research Paper

Matt Lazar

5/13/96

8th Hr.

Photosynthesis

When you and me eat, we find our food. When plants eat, they make their own food and energy. They make their food and energy through a process called photosynthesis. Through photosynthesis oxygen is also produced. Photosynthesis is “a process in which green plants synthesize carbohydrates from carbon dioxide and water….The reverse of this reaction provides energy for plants, for animals that eat plants, for animals that eat animals that eat plants” for animals that eat animals that eat animals that eat plants, etc. (Levine 726) All humans rely on these plants to produce oxygen from photosynthesis. The presence of light and of the green pigment chlorophyll makes the change of carbon dioxide and water to glucose and oxygen possible. It was Jan Ingenhouz with Jean Senebier in Geneva that founded the basic gist of the theory of photosynthesis in plants.

My experiment involves testing different brands of plant food on plants to see what brand of plant food makes the plant grow the tallest. I will test three types of plant food on three sets of plants and one set with no food. I will water the plants all the same amount and let all the plants get the same amount of sun, then measure the height of all the plants at the end of six weeks and record the data.

The first step of photosynthesis is the absorption of light by a chlorophyll molecule. “The energy of the absorbed photon is transferred from one chlorophyll molecule to another until it reaches a site called a reaction center….One oxygen molecule is produced per eight photons absorbed.” (Alberty 708) James Huheey, professor at the University of Maryland, talks about chlorophyll in his book Inorganic Chemistry:

“Chlorophyll absorbs low-energy light in the far red region….Such absorption serves a twofold function: (1)The energy may be passed along to the chlorophyll system and used in photosynthesis; (2)It protects the biological system from photochemical damage.” (629)

“Chlorophyll a and chlorophyll b contain networks of alternating single and double bands, and have strong absorption bands in the visible part of the spectrum….,” says Robert Alberty, who is a professor of chemistry at the Massachusetts Institute of Technology. (708)

Photosynthesis, “…which occurs entirely in the chloroplasts of green cells, involves a number of steps catalyzed by enzymes. The chloroplasts contain chlorophyll a, chlorophyll b, carotenes, electron carriers, and enzymes, and have internal membranes that keep reactants separated,” says Alberty. (708)

James Huheey talks about some “features of the chlorophyll system which enhance[s] its usefulness as a pigment in photosynthesis:

“First, there is an extensive conjugation of the porphyrin ring. This lowers the energy of the electronic transitions and shifts the absorption maximum into the region of visible light. Conjugation also helps make the ring rigid and thus less energy is wasted in internal thermal degration.” (631)

“In order for phosphorescence to occur there must be an excited state with a finite lifetime. If such an excited state is available then there is time for a chemical reaction to take place to take advantage of the energy prior to phosphorescence….The presence of a metal atom is necessary in order that phosphorescence takes place.” (Huheey 631)

“Chlorophyll contains a conjugated ring system that allows it to absorb visible radiation….” (Levine 726) In Inorganic Chemistry, James Huheey reports about ring system:

“The chlorophyll ring system is a porphyrin in which a double bond in one of the pyrrole rings has been reduced. A fused cyclopentanone is also present….In addition, other pigments such as carotenoids are present which absorb higher energy light.” (629)

The exact frequency of the light that is absorbed by the chlorophyll depends upon the nature of the substituents on the chlorophyll.

Photosynthesis is a crucial process that is necessary for the human race and other races that breath the oxygen that the plants produce to live. Photosynthesis is a complex process that we know only broad details about. Chlorophyll and light are what is needed for plant to photosynthesize. I think that my experiment will prove the best brand of plant food out of the three. The best brand would be the one that makes the plant grow highest. So consider just how important that green plants really are to the human race and their survival on the earth.

Alberty, Robert A. Physical Chemistry. New York: Wiley, 1983.

Asimov, Isaac. Photosynthesis. New York: Basic, 1968.

Brock, William H. The Norton History of Chemistry. New York: 1993.

Huheey, James E. Inorganic Chemistry. New York: Harper, 1972.

Levine, Ira N. Physical Chemistry. New York: McGraw, 1978.