Essay, Research Paper: Photosynthesis

Photosynthesis
Photosynthesis is the conversion of light energy to chemical energy which is then
stored in the form of glucose or other organic compounds. Photosynthesis occurs in
plants, algae and certain prokaryotes. Photosynthesis is generally the opposite of
respiration where photosynthesis starts with CO2, light energy, and water to yield glucose,
water and oxygen. This is the general equation for photosynthesis: 6CO2 + light energy +
12H2O = C6H12O6 + 6O2 + 6H2O.
In plants photosynthesis occurs in the thylakoid membrane. There are two
reactions in the thylakoid membrane: the light dependent reactions, and the light
independent reactions. In the light dependent reactions, light excites an electron into a
higher energy state. This electron is then captured by an electron acceptor and the energy
released during it’s fall back down to ground state is harvested to create ATP. In the light
independent reactions, the energy made from the light dependent reactions is used to make
glucose, a six carbon sugar. The carbon comes form the break down of CO2 and the
oxygen is released into the air.
However, there are imperfections. Sometimes the light independent reactions uses
O2 instead of CO2 which produces a two carbon compound. This compound is useless to
the plant and it uses more energy to break it back down to CO2. The process where O2 is
used instead of CO2 is called photorespiration. Plants which have a lot of photorespiration
are known as C3 plants and are very slow growing. Fast growing plants, plants that have
little photorespiration, are known as C4 plants.
This experiment tested how much CO2 is consumed in C3 plants versus C4 plants.
The null hypothesis is that in C3 plants will consume as much CO2 as C4 plants. The
alternate hypothesis is that C4 plants will consume more CO2 because photorespiration is
very little.


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