Energy, Metabolism, and Cells

Energy, Metabolism, and Cells

Unit 2 Individual Project

SCIE206-1204A-08: Biology

Kandyce Livingston

American Intercontinental University

Abstract

The following essay will address three separate, specific topics as assigned by the course instructor. First, the essay will explain how photosynthesis and respiration are linked in order to provide energy from food. A complete description of photosynthesis and aerobic respiration will be provided along with a description of how the two processes are linked between plants and animals based on reactants and products (water, carbon dioxide, glucose, oxygen) of both pathways. A description of how energy is transferred from sunlight to ATP, from ATP to sugars, and from sugars to cells will also be presented. Second, the essay will provide a discussion of the role of fermentation in allowing an organism to generate energy for its cell(s) in the absence of oxygen. This will also include any reactions required for this process, and an explanation of how the energy from the sun ends up as chemical energy for the anaerobic organism or cell. The third and final topic will explain how an enzyme catalyzes a reaction, will address the three main steps of the cycle of enzyme-substrate interactions, and explain how enzyme activity is regulated by the cell.

Energy, Metabolism, and Cells

1. Explain how photosynthesis and respiration are linked in order to provide you with energy from the food you eat. Include complete descriptions of photosynthesis and aerobic respiration. Describe how these two processes are linked between plants and animals based on the reactants and products (water, carbon dioxide, glucose, and oxygen) of both pathways. Include a description of how energy is transferred from sunlight to ATP, from ATP to sugars, and from sugars to your cells.

Photosynthesis is a combination of carbon dioxide, water, inorganic salts and light energy, all of which are used to synthesize more complex organic materials (biology-online.org, 2009). Further more, photosynthesis can also be described as a process where carbon dioxide, water and light energy are used to create and bind carbohydrates like energy-rich glucose, and produce oxygen as a waste product. The light energy, which comes from sunlight, is received through the chlorophyll and other accessory pigments and the reactions can be either light reactions or dark reactions. Providing additional details, light reactions are a series of biochemical reactions in photosynthesis where light energy is required for the conversion into chemical energy, or ATP and NADPH. However, dark reactions are just the opposite in that light is NOT required to continue to produce organic molecules from carbon dioxide (biology-online.org, 2009). Photosynthesis is important to plants, algae and some bacteria that can produce their own food through inorganic compounds. These photocytotrophs use light energy in order to avoid consuming or depending on nutrients derived from other living organisms.

Aerobic respiration can be described as cellular respiration that must have oxygen to create energy (biology-online.org, 2008). It is also the process of energy generation by the full oxidation of nutrients through the Krebs cycle, where oxygen is the final electron acceptor. Simply put, it is a method used by plants as well as animals where sugars are broken down in forms of energy that can be used as such. Aerobic respiration takes oxygen to break down glucose molecules into forms of energy which are then ready and available to be used by plant and animal cells as fuel for their necessary functions. In eukaryote cells aerobic respiration occurs in the mitochondria, but in prokaryote cells it occurs in the cytoplasm (biology-online.org, 2008).

Photosynthesis is a process in which plants use their chlorophyll to soak in the sun's energy to then convert to glucose (eHow.com, 2012). In this process, oxygen is the by-product. During this process, plants retrieve small molecules from their environment and these molecules are then bonded together using light energy. The incoming light energy is turned into the energy that, in turn, is binding the new molecules. These new molecules are then used by organisms as their energy or fuel (McDarby, 2001-2012). In summary, water and carbon dioxide are obtained from an organism's surroundings, the soil in which it lives, and/or from the atmosphere. Carbon dioxide (CO2) and water (H2O) are then synthesized via the light reaction in the chlorophyll for the production of glucose (C6H12O6) and the release of oxygen (O2). This process can be broken down as follows:

6 CO2 + 12 H2O + light energy  6 C6H12O6 (glucose) + 6 O2 + 6 H2O

As a result of this process, glucose is stored as a reserve of energy that may be necessary during periods of darkness. It is also a major part of a cells' structure in that cell walls are composed of starches. Oxygen is released as a by-product and/or waste product.

Aerobic respiration is a mirror-image or the opposite reaction of photosynthesis. It uses glucose and oxygen to access energy stocked up in other glucose and then releases carbon dioxide and water (McDarby, 2001-2012). In aerobic respiration, plants and animals create usable forms of energy by having oxygen break down glucose. This takes places in the mitochondrion where glucose is further converted to ATP and carbon dioxide, water, and ATP become by-products (eHow.com, 2012). This process can be simplified as follows:

C6H12O6 + 6 H2O + 6 O2 ----------------> 6 CO2 + 12 H2O

------- Energy to ATP

Moving on, during photosynthesis, light breaks through the cell and passes into the chloroplast. Here, the light energy is picked up by the molecules where some light energy is then turned into chemical energy. During this process, a phosphate combines to a molecule for the creation of ATP. The third phosphate chemical bond has new chemical energy which allows ATP to give energy to other photosynthetic reactions that are converting carbon dioxide into glucose (A Primer on Photosynthesis, n.d.) This shows how energy is transferred from sunlight to ATP, then from ATP to sugars, and finally, from sugars to the cells.

In conclusion, photosynthesis and aerobic respiration are linked in order to provide a person with energy from the food they consume.