The Connection Between Cellular Respiration and Photosynthesis
The sun is the source of energy for every living thing on the planet, but not every living thing can directly make energy from sunlight. Cellular respiration and photosynthesis are interdependent on one another and work together to produce ATP which fuels the functions for all living things.
Cellular respiration is the process of turning food molecules into ATP in the mitochondria of the cell. This process is done through several reactions, which can be simplified into the equation glucose plus oxygen yields carbon dioxide, water, and ATP. This entire cycle can be identified in three processes: glycolysis, krebs cycle, and the electron transport train. During glycolysis, the glucose is broken down in the cytosol, forming into two pyruvates through a reaction using the enzyme pyruvate dehydrogenase. This step produces two net ATP and 2 NADH electron carriers that will be used in the electron transport train. Next the pyruvate is transported inside the mitochondrial matrix to be used in the Krebs Cycle, the pyruvate is converted into Acetyl CoA where it is broken down into carbon dioxide. The high-energy electrons that were released are added to the electron carriers, NADH and FADH2, and used to assemble two ATP (substrate-level). Finally, in the electron transport chain, also known as oxidative phosphorylation, hydrogen ions are pumped into the intermembrane space to create an H+ gradient. In this stage of cellular respiration, the electron carriers that were produced in the Krebs cycle donate their energy to produce 36-38 ATP, these ATP are energy that every organism uses to carry out biological functions.
Unlike cellular respiration, photosynthesis is a process used by autotrophs to make their own food needed to sustain life. In the chloroplast do the cell sunlight, water and carbon dioxide react to make glucose and release oxygen. This process can be classified into the light reaction and the calvin cycle (dark reactions). During the light reaction, which takes place in the thylakoid, light energy is used to oxidized water and release oxygen. The electrons released during this reaction are transferred to ATP and NADPH. Next, the ATP and NADPH are used in the stroma during the calvin cycle to turn carbon dioxide in the sugar molecule: glucose.
The connection between photosynthesis and cellular respiration is that the products for one reaction are the reactions for the other. This creates a cycle where one process fuels the other. Photosynthesis makes the glucose that is used in cellular respiration to make ATP. During the process of breaking down the glucose releasing carbon dioxide as a by-product. Photosynthesis requires carbon dioxide to form glucose and releases oxygen as a by-product. The oxygen released during photosynthesis is used by most organisms for cellular respiration. This makes cellular respiration and photosynthesis are key components of the carbon cycle. Their process helps to keep the levels of oxygen and carbon dioxide in the atmosphere stable and able to stain life.
