The Change of Rates of Photosynthesis in Cyanobacteria Synechocystis with Chemical Inhibition
This experiment examined the effects caused by inhibition in the production of photosynthesis in the cyanobacteria Synechocystis. It was exposed to different levels of light, varying from zero to 400-umol photons m-2s-1. These different light levels helped measure the respiration production and the photosynthetic production. Several trials were done with no inhibitors added to the cyanobacteria, a trial with glycoaldehyde and a trial with DCMU added to the cyanobacteria were also done. The results showed that there was a slight inhibition of photosynthetic production that was caused by the glycoaldehyde and a more significant inhibition of photosynthetic production that was caused by DCMU. On the other hand, the trials that were done with no inhibitors demonstrated some slight decreases at certain light levels, which showed to be photoinhibition.
The most important metabolic pathway in plants is photosynthesis. This implicates several proteins and enzymes, as it is a complex process. The entire process takes in carbon dioxide, water and light energy and then releases or creates glucose, water and oxygen (Stewart et al., 2017).
6CO2 +12H2O +(at least) 48photons→ C6H12O6 +6H2O + 6O2
Photosynthesis is a process that is compromised of several different chemical reactions that are catalyzed by enzymes. It can be separated into two major stages, Photosystem I and Photosystem II, which are present in the thylakoid membrane in the chloroplast. Photosystem II contains ten major protein sub-units and is the first stage.
Photosynthesis is effected by several different things, such as temperature, substrate availability, light levels, presence of inhibitors (Blankenship, 2002). All these different effects cause photosynthetic production to be highly variable. Usually, as light levels increase this results in an increase in the rate of photosynthetic production, which in turn will eventually reach a point of saturation, where the photosynthetic production will no longer increase. This steady increase however is possible to slow down with the use of chemical inhibitors.
Chemical inhibitors that are used are substances that prevent a certain step in the photosynthetic production that causes a decrease and not an increase in oxygen (Blankenship, 2002). Along with this, another aspect that can that can lower or slow down the rate of photosynthesis is photoinhibiton, which is when the light levels themselves slow the rates of photosynthetic production. This occurs when the photosystem II complex D1 protein is exposed to light for a prolonged amount of time and is then damaged (Kato, 2012). The complex replaces it continually with the D1:2 but when the intensity of the light keeps increasing the rate at which it is destroyed outweighs the rate at which it is replaced resulting in a decrease in the photosynthetic production.
The chemical inhibitors...