Respiration Vs Photosynthesis

Just as a lion must hunt his prey for energy, a cell must also carry out several functions in order to synthesize energy. Plant cells go through photosynthesis while most eukaryotic cells go through respiration. Though it may not seem significant on a macroscopic level, it is certainly paramount to the survival of all living things. Adenosine Triphosphate (ATP) is a phosphoralized nucleotide that is used as a means for cells to store energy for later use. Although the structure itself is not much different than RNA, it is when its bonds are broken that a significant amount of energy is released for a cell to use as fuel.

In order to synthesize ATP, an animal cell will go through a process known as cellular respiration. In the initiating stage of respiration, a glucose molecule is broken down and isomerizes several time until it becomes 2 pyruvate molecules in a process known as glycolysis. Since the bonds in glucose are not easily broken, the energy released when torn apart is used to create a small amount of ATP. After the pyruvate has been created, it goes on to the mitochondria where it is broken down even more and forms carbon dioxide and water in the aerobic Krebs cycle. After proceeding through the Krebs cycle, it creates more ATP, but not enough for significant functionality. What remains of the pyruvate, reduced coenzymes, enters a group of proteins that carry electrons through several redox reactions in the mitochondrion's membrane known as the electron transport chain. These proteins create a concentration gradient along the membrane by passing electrons from the coenzymes formed in the Krebs cycle. The energy given off is then used to pump ionized hydrogen atoms out to the mitochondria's inter-membrane, making the outside more positive than the inside. This allows for a current of charged hydrogen to pass across the membrane through a complex known as ATP Synthase. Through the process of chemiosmosis, ATP is produced as the protons move down the mitochondrial membrane through the ATP Synthase. The result is a large amount of ATP that allows the cell to carry out vital functions.

Most of cell respiration occurs in the mitochondria, but organism without one, like plants, must create ATP through alternate means. Photosynthesis takes place in the chloroplast, which, like the mitochondria, is composed of a double layered membrane important for the creation of ATP. Within the chloroplast are sacs used to absorb light for energy known as thylakoids. What makes this possible are light absorbing pigments within the thylakoid known as photosystems. Like the electron transport chain found in the mitochondria, the thylakoid membrane contains proteins used to move electrons across it, with some containing chlorophyll. Chlorophyll (a), a chlorophyll molecule capable of passing electrons to other molecules, plays a key role in the plant cell cycle of producing ATP due to its ability to reach an excited state when in contact