Photosynthesis Analytical Essay
Photosynthesis is a plants way to produce the glucose that it needs for cellular respiration because plants do not get the energy that they need from food, they have to make it by transforming carbon dioxide and water into glucose water and molecular oxygen. The formula for this is:
6CO2 + 12H2O → C6H12O6 + 6H2O +6O2
Photosynthesis is a redox reaction, in other words, the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. Oxidation reduction reactions or redox reaction occur when there is loss of electrons equates with oxidation and gain of electrons equates with reduction. Electrons will move from one atom to another.
Cellular respiration is occurs simultaneously with photosynthesis in plants but is almost the complete opposite. Cellular respiration turns glucose into energy while photosynthesis turns energy, water and carbon into glucose. Photosynthesis takes advantage of the energy in light using photosystem II and photosystem I. Photosystem II is first in this process but I named otherwise because it was discovered second. First is the Calvin cycle. The process of turning light into energy begins when light in the form of a photon hits the reaction center of photosystem II in the thylakoid in a chloroplast. Cellular respiration on the other hand, begins in one of three stages. Cellular respiration begins with glycolysis, the splitting of glucose that occurs in the cytosol. First glucose is split into two 3 carbon sugars. Then oxidized into two molecules of pyruvate. NAD+ is reduced to NADH in the process. Two molecules of ATP are used to lower the energy of activation. Four ATP are produced as the bonds are broken and form because of phosphate level phosphorylation. Next is what is called the intermediate step. This occurs in the mitochondrial matrix. Oxygen is required for this process to occur. First the 3 carbon pyruvate enters the mitochondrial matrix via active transport. The carbon compound is oxidized, reducing NAD+ to NADH forming a 2 carbon acetyl molecule that then bonds to coenzyme A. Then in krebs cycle also known as the citric acid cycle, acetyl coenzyme A bonds to a 4 carbon acetyl molecule. Coenzyme A is then released and recycled back into the intermediate step. During this process 3NAD+ is reduced to 3 NADH and 1FADH is reduced to FADH2. One ATP is made and 2CO2 is released. The krebs cycle occurs twice for one molecule of glucose because 1 molecule of glucose produces 2 pyruvate and is mainly the process to get rid of CO2.
The best way for me to learn this material was an input output chart I made for cellular respiration. This helped me to remember what materials went in and turned into what. It was easiest just to remember the input such as if I knew that one NAD+ went in I could easily tell that one NADH would come out. For photosynthesis the best thing for me was a picture in a packet that was given out in class that featured an illustration of photosystem II and photosystem I with arrows showing the flow of energy and products in the reaction. To me this all is the explanation of why we really need oxygen and why we exhale carbon dioxide. This whole unit has brought together for me a better understanding of the near symbiotic relationship between plants and animals. Carbon dioxide and water and sunlight to glucose, water and oxygen to carbon dioxide again... All life lives together.
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