I took out the microscope once again. This time, I took a look at some leaves in my backyard! Here, we are observing chloroplasts. So what are chloroplasts? Chloroplasts are membrane-bound organelles found in plant cells that conduct photosynthesis, which is the process by which light energy from the sun is converted into chemical energy. This results in the production of oxygen and energy-rich organic compounds that the plant needs.
Chloroplasts are a type of plastid, and are oval shaped. Clearly, they are very green. This is because of two pigments found inside of them, chlorophyll a and chlorophyll b. These are the pigments that absorb light for photosynthesis. Also, another important pigment called carotenoids are very important for plants. These carotenoids serve as kind of a "carrier", as they bring solar energy to the chlorophyll.
Structure of Chloroplasts
Chloroplasts are enclosed in a chloroplast envelope, which is a double membrane with a gap between the two membranes called the intermembrane space. The thylakoid membrane, an internal membrane extensively folded and characterized by the presence of closed disks, is also present. In most higher plants, the thylakoids are arranged in tight stacks called grana.
How chloroplasts drive photosynthesis
Photosynthesis has two important reactions: light independent and light dependent. The thylakoids are very important for the light dependent reactions as it houses chlorophylls and different protein complexes that make up the electron transport chain (ETC), which is specialized for light-dependent photosynthesis. Light from the sun strikes the thylakoids, exciting the chlorophyll pigments within it. This causes the chlorophyll to release electrons, that enter the ETC. In the end, the ETC produces ATP through the phosphorylation of ADP. Along with ATP, the ETC also produces NADPH.
After the light dependent reactions have concluded, the light independent reactions take place in the stroma. Using the energy from the ATP and NADP, these two molecules drives a chemical pathway that uses carbon from the atmosphere to build glyceraldehyde-3-phosphate (G3P), a three-carbon sugar. The G3P is used to build other sugars like glucose and organic molecules that the plant can use for nutrients.
Conclusion
In the end, chloroplasts are crucial to our world, as they drive the survival of plants through photosynthesis. Without photosynthesis, plants wouldn't be able to produce the oxygen we need to live.
Sources:
“Chloroplast.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/chloroplast.
“Photosynthetic Cells.” Nature News, Nature Publishing Group, https://www.nature.com/scitable/topicpage/photosynthetic-cells-14025371/.
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