Photosynthesis:
Energy from light!
Photosynthesis is the process of turning the energy of light into sugars. Just like normal table sugar, the sugars made by plants are packed with energy. Plants are not the only forms of life that utilize photosynthesis, algae and microorganisms are capable of performing photosynthesis.
Why it's Important
Humanity is more dependent on photosynthesis than ever before. 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. Realize that nearly all of the energy needed for life comes from our sun. This is an enormous amount, and only a fraction of that light energy is actually used.
Overview
The basic formula for the process of photosynthesis is as follows:
Carbon Dioxide + Water ---> Sugar + Oxygen
(In the Presence of Light + Chlorophyll)
There are two parts to photosynthesis, Light Reactions and the Calvin Cycle. The Light
Reactions capture the energy of light and transfers the energy to short-lived energy-molecules. Those
energy-molecules then powers the Calvin Cycle. The Calvin Cycle takes available Carbon Dioxide and incorporates it
into a sugar containing six carbons. This entire process takes place in the chloroplasts of plant cells, which
hold the chlorophyll that makes this all possible.
Figure 1 shows the two sides of photosynthesis. In goes Light, water (H20), carbon dioxide (CO2), and out pops
oxygen and sugar. In the bottom middle of the figure is ATP and NADPH. Those are the energy-molecues.
NADP+, ADP, and P are just the used forms of them that become regenerated.
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
Chlorophyll : The molecule responsible for photosynthesis
The structure of molecules determines what kind of energy it can absorb. It can be any kind of radiation like microwaves or ultraviolet light. The structure of chlorophyll allows it to absorb the blue and red visible lights. Because it does not absorb green light, it is reflected back and produces the green color present in plants. When light strikes chlorophyll, it excites an electron. This excited electron will be transported to proteins that can step-wise take the energy from the electron and put that energy into other molecues: ADP and NADP+
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