How photosynthesis and respiration are linked And how do they to provide you with energy from the food you eat - Essay Example

During photosynthesis, sunlight causes the water and carbon dioxide to be changed into oxygen and sugar (glucose) (Audesirk, Audesirk, and Byers, 2008).The process starts with absorption of light energy by proteins (known as photosynthetic reaction centers), which have chlorophylls. A part of light energy collected by chlorophylls is stored as adenosine triphosphate (ATP), while rest of the energy is used for breaking electrons present in water molecules, obtained by plants from soil. These electrons then take part in reactions that change CO2 obtained from the atmosphere into organic compounds.

The chemical equation that represents photosynthesis is as follows: Sunlight + chlorophyll 6 CO2 (carbon dioxide) + 6 H2O (water) C6H12O6 (glucose) + 6 O2 (oxygen) Respiration is a catabolic process, where organic compounds are broken down and energy is released. In this process oxygen and glucose (produced by photosynthesis) are used to make carbon dioxide and water, and adenosine triphosphate (ATP) is released as chemical energy, (released from molecular glucose) which is completely broken down by aerobic respiration.

When ATP is broken down by human body cells to form adenosine di-phosphate or ADP, energy is released along with a phosphate group. Thus, ATP is the source of energy for all human body cells, and this energy is used for maintaining all body functions. The equation showing the process respiration is as follows: C6H12O6 (glucose) + 6 O2 (oxygen) 6 CO2 (carbon dioxide) + 6 H2O (water) +36 ATP Therefore, respiration and photosynthesis are complementary reactions. Respiration needs glucose and oxygen produced by photosynthesis, while photosynthesis needs carbon dioxide and water that are products of respiration, and both processes combine to produce energy. 2. What is fermentation?

Some organisms and cells use glycolysis (known as fermentation) to produce chemical energy from glucose created during photosynthesis (where energy is derived from sunlight), even without the presence of oxygen. Fermentation starts with breaking down of a glucose molecule, and the entire set of reactions is termed as glycolysis (Alcamo, 2003).  Glycolysis involves ten chemical reactions (fig 2), controlled by various enzymes, and energy is released as two ATP molecules for each molecule of glucose that is divided into half, and the entire process takes place in absence of oxygen.

Alcoholic fermentation is seen in yeast, which results in alcohol and CO2. On the other hand, in human bodies (in muscle cells) lactose fermentation takes place, which produces lactic acid causing pH levels to turn acidic. Under such circumstances, an individual starts experiencing muscle cramps and tiredness (Alcamo, 2003).  The process of fermentation is represented pictorially as follows: Fig 2: The process of Glycolysis and fermentation (Yim and Glover, “The Biochemical process,” 2003). 3. Enzymes Biological catalysts also known as enzymes help in carrying out various chemical reactions, taking place within living cells.

Enzymes are large protein molecules, containing hundreds of amino acids. Often there is also a non-protein group (a vitamin co-enzyme or a metal cofactor), which is required during catalysis for decreasing the activation energy (Bisswanger, 2008). When an enzyme-catalysis takes place, the substrate joins