Photosynthesis:

Energy from light!

     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. The overview discusses the location of where photosynthesis occurs and what two stages work in tandem to make photosynthesis possible.

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 if one were to follow what something or someone ate continuously down the food chain. Our way of life revolves around a process that we are actually unable to perform. Without photosynthetic organisms, 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, which are a small bodies within the cell that performs certain duties. The chloroplasts are the organelles responsible for photosynthesis. These chloroplasts also contain chlorophyll, which is the molecule responsible for the capturing of light energy.

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 Inter-membrane 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

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 7^th 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