Energy, Metabolism and Cells - Essay Example

Furthermore, there are four ways by which enzyme activity is regulated by the cell. Photosynthesis and Aerobic Respiration Photosynthesis and aerobic respiration are two intracellular processes that work hand in hand in order to bring about the chemical transformation of sunlight into usable energy, in the form of ATP (“Photosynthesis and Respiration,” 1999). Basically, photosynthesis is the process through which plants convert sunlight to glucose, with the chemical equation: 6H2O + 6CO2 ?

C6H12O6 + 6O2. ATP for use by the plant itself is also produced by the light reactions of photosynthesis (Carter, 1996). However, since the main product of the photosynthetic process – glucose or sugar, C6H12O6 – needs further conversion into a form considered usable by the plant and animal body, this conversion is made possible by the process that complements photosynthesis: aerobic respiration (Farabee, 2007). Through aerobic respiration, ATP is produced from glucose. The chemical equation for aerobic respiration is C6H12O6 + 6O2 ?

6H2O + 6CO2 + 36 ATP (Burkett, 2005). This means that in the process, 36 units of ATP or energy is produced. In short, plants produce glucose through photosynthesis, and this glucose is consumed and utilized by the plant and animal to produce ATP through aerobic respiration. Photosynthesis itself is a complex process made up of the light and dark reactions. The Light Dependent Process, or Light Reactions, uses the direct energy of sunlight to produce energy carrier molecules – ATP and NADPH – needed in the second process, the Light Independent Process, or Dark Reactions, where glucose, or C6H12O6, are produced (Farabee, 2007).

The Light Reactions in the thylakoid membrane of the chloroplasts, the require sunlight to strike the chlorophyll and carotene molecules in the leaves of plants in order to trigger a series of reactions that will eventually produce ATP and NADPH (Farabee, 2007). In the Light Reactions, the hydrogen atoms of water, H2O, are also removed for use in reducing NADP+ to NADPH (Kimball, “The Thylakoid,” 2011). In the ensuing Dark Reactions or Calvin Cycle, which occur in the stroma, carbon dioxide is captured and combines with RuBP, a 5-carbon chemical, to finally produce a 6-carbon glucose, C6H12O6 (Farabee, 2007).

Now, in order for this glucose to be usable, it must be consumed by the plant itself or the animal but it must first be used to produce ATP through aerobic respiration. Aerobic respiration is a three-stage process where ATP is produced during each stage. Glycolysis, the first of the three stages, occurs in the cytoplasm and involves a 10-step process that ends up with the breakdown of glucose, C6H12O6, into two pyruvic acid molecules, C3H4O3, and in the process produces a net of 2 ATP and 2 NADH (Gregory, 2011).

Each of the two pyruvic acid molecules now goes to the matrix of the mitochondrion for an intermediate process known as pyruvate oxidation or oxidative phosphorylation, and produces CO2 and an acetyl group. The acetyl group then combines with CoA to form Acetyl CoA, and producing 2 NADH in the process. In fact, there are actually two Acetyl CoA molecules at the beginning of the next stage, the Krebs Cycle, so there are two Krebs Cycles from one Glycolysis process (Burkett, 2005). The Krebs Cycle, which occurs in the matrix of the