As we all know, photosynthesis is used to convert light energy to chemical energy. It uses carbon
dioxide, water, and sunlight to produce oxygen as well as carbohydrates such as glucose. The
photosynthesis equation is as follows: H
O + CO
O) + O
The molecule that is
used to capture and absorb the sunlight is chlorophyll. This photoreceptor is found in the
chloroplasts of green plants and is what gives green plants their color. The thylakoid membrane
of the chloroplasts is where the “photo”, or light dependent, part of photosynthesis takes place.
The “synthesis”, or light independent, part takes place in the stroma, which is the fluid that
surrounds the thylakoids.
In the Hills Reaction, Robert Hill demonstrated that during photosynthesis water is the source of
electrons in the light reaction and not carbon dioxide. It showed that reactions giving up oxygen
could occur without reactions that use carbon dioxide, giving way to the difference between light
dependent and light independent reactions. Aside from the Hills Reaction, we know that during
photosynthesis, electrons that were raised to a higher energy level are being moved around and
electron-acceptor molecules are being reduced and oxidized, thus forming NADPH. NADP
DPIP also play an important role. DPIP replaces NADP
as an electron receptor in light
reactions. When DPIP is oxidized it produces a dark blue color. When it is reduced, it changes
from blue to colorless.
Looking at plants such as trees, I noticed that there must be an important reason why leaves are
grown on stems and branches. It allows the light to reach them faster, which must be important
since, as we just mentioned, light is an essential part of photosynthesis. With the light reaching
the leaves directly, chlorophyll may begin to absorb the sunlight faster meaning the electrons
would be boosted to a higher energy state more quickly. My lab partners and I believe that direct
contact with light speeds up photosynthesis. For example, in a normal photosynthesis
experiment, a large flask filled with water acts as a heat sink, which may slow down the process.
Heat sinks absorb some of the heat given off from, in this case, the lamp. My lab partners and I