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Kyle

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on March 27, 2010 at 8:55:14 pm
 

 Photosynthesis:

Energy from light!

 

Here, plants use the energy from  sunlight to power the formation of nutrients.

 

     Photosynthesis is the process of turning the energy of light into sugars. These sugars are packed with energy usable by plants, people, or any plant-eating critter. Here are some basics of why photosynthesis is important, including a quick overview of what is occurring during photosynthesis.

 

Why it's Important

 

The fossil fuels that are the cornerstone of our energy began as carbon dioxide from the atmosphere. Through photosynthesis, ancient forests turned that carbon dioxide into organic compounds, leading to the their underground transformation into the crude oil we use today. Humanity is more dependent on photosynthesis than ever before. Thus, any product that stems from crude oil can be attributed to photosynthesis. All of our food's energy content can also be attributed to photosynthesis. Our way of life revolves around a process that we are actually unable to perform. Without photosynthetic organsisms, life on Earth would only exists among bacteria whose energy source is not related to the sun.

 

 

Overview

 

 The basic formula for the process of photosynthesis is as follows:

              

Carbon Dioxide + Water + Light ---> Sugar + Oxygen

(In the Presence of Chlorophyll)

 

          

Figure 1 http://static.howstuffworks.com/gif/irrigation-photosynthesis.gif

 

 

The Chloroplast : The site of photosynthesis

 

     All forms of life are built by cells. A cell is the smallest portion of an organism. In more complicated forms of life, such as plants, people and bugs, different types of tissue are made by different types of cells that have specialized tasks. In trees, for example, the cells that make the trunk are specialized for transporting nutrients up and down the tree, while the leaves are wide and broad to capture light for photosynthesis. Those leaves have something that the bark cells do not, and those are chloroplasts. Chloroplasts are organelles. An organelle is a small body that performs certain duties within the cells. The chloroplasts are the organelles responsible for photosynthesis. Within these organelles lies the chlorophyll, which is where this entire process begins.

 

 

Structures found within the Chloroplast

 

  • Thylakoids - Disc-shaped membranes stacked into Granum. This is where photosynthesis actually takes place.
  • Lumen - The are inside of the thylakoids.
  • Stroma - The 'open-space' within the chloroplast. 
  • Outer/Inner Membrane and Intermembrane Space - These two membranes serve as gates for transporting things in and out of the chloroplast.
  • Stroma Lamellae -  connects the thylakoids to each other

     

 

 

 

 

 

 

Figure 2: http://micro.magnet.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg

 

Photosynthesis in Two Steps : Light Reactions and the Calvin Cycle

 

Taking a quick review of the earlier equation: Carbon Dioxide + Water --> Sugar + Oxygen. This is actually condensed from two equations, coming from the two ends of photosynthesis: Light Reactions and Calvin Cycle

 

1. Light Reactions - Uses Light energy to recharge molecules.

 

Water + Energy-poor Molecules+ Light -> Oxygen + Energy-RICH Molecules

 

2. Calvin Cycle - Uses those energy-charged molecules to power the creation of a sugar.

 

Carbon Dioxide + Energy-RICH Molecules ---> Sugar + Energy-poor Molecules

 

Put those two equations together....

 

Water + Energy-poor Molecules +Carbon Dioxide + Energy-RICH Molecules + Light ---> Oxygen + Energy-RICH Molecules + Sugar + Energy-poor Molecules

 

Now, because the energy-poor/rich molecules are present on both sides of the equation, they can be taken out to provide a net result of:

 

Carbon Dioxide + Water + Light ---> Sugar Oxygen

 

This occurs in chloroplasts, which contains chlorophyll. It is the presence of chlorophyll which makes this all possible. The sugars produced can be used immediately or stored for long periods of time. When those sugars are stored for a long amount of time in plants, it is referred to as starch. 

 

 

In Conclusion

 

The process of photosynthesis is perhaps the most important aspect of life on Earth. This could not be emphasized enough. All energy consumed by non-photosynthetic beings can be traced to something able to perform photosynthesis, whether it is a plant or something else. Finally, there is one more end to photosynthesis. Our bodies, in fact have its own energy-using process called Cellular Respiration. This process uses up the sugar and oxygen, while creating carbon dioxide and water. With Photosynthesis and Cellular Respiration working together, we basically get life in a nutshell.

 

 

 

Sources:

 

Becker, W., Kleinsmith, L., Hardin, J., & Bertoni, G. (2009). Chapter 11 - Phototropic Energy Metabolism: Photosynthesis. The World of the Cell 7th Ed. 293-320.

 

Blankenship, R.E., Berkowitz, G., Govindjee,  Portis, A., & Shopes, R.J.  (2007). Photosynthesis. In McGraw-Hill’s Access Science: Encyclopedia of Science & Technology Online. Retrieved February 25, 2010, from http://www.accessscience.com.ezproxy.library.unlv.edu/content.aspx?searchStr=photosynthesis&id=511700

 

 

 

 

 

 

 

 

 

 

 

 

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