All organisms require energy to live. However, different organisms have different ways to obtain energy. Autotrophs such as plants and algae produce their own food as energy, while heterotrophs like humans and other animals can’t make their own food, and must eat to get energy. We know clearly how consuming food is important for us to keep energized, but how do autotrophs produce their own food?
(image provided by Pixabay, copyright-free)
Let me introduce you to this amazing process: photosynthesis, in other words, how autotrophs such as plants get energy.
Introduction to Photosynthesis
An organelle, or a specialized structure within a living cell of a plant, called the chloroplast, is extremely important for the performance of photosynthesis. It is where photosynthesis takes place.
To be more detailed, chloroplasts contain Thylakoid/Grana and Stroma.
In the image shown above, the coin-like structure is the thylakoid; a stack of thylakoid is called grana; stroma refers to the fluid surrounding grana within the chloroplast.
During photosynthesis, plants take in water and carbon dioxide and convert them into oxygen and glucose. Oxygen is released by the plants and can be breathed in by us and other animals, and glucose is the energy source for plants.
It takes three steps to perform photosynthesis:
Chlorophyll, or the green pigment in chloroplasts that make plants look green, absorbs sunlight, or light energy.
Light energy absorbed undergoes a process called the Light Dependent Reaction, and is converted to chemical energy.
During another process called the Calvin cycle, glucose is made.
Light-Dependent Reaction and Calvin Cycle
The light-dependent reaction occurs in the light only. During this process, water molecules are split, and oxygen is released. Light energy is stored temporarily in inorganic energy carriers, NADPH and ATP.
Different from the light-dependent reaction, the Calvin cycle could occur in the light or the dark. During this process, Carbon dioxide enters, and glucose is formed. The energy that is stored in NADPH and ATP is released to the organic compound, or glucose.
**ATP is a chemical energy storage molecule that releases energy when the bonds between the phosphates are broken; NADPH carries electrons and stores energy.
Factors that affect the rate of photosynthesis
Many things occur under certain conditions only, and many factors would affect things. Photosynthesis is not an exception. What would affect the rate of photosynthesis?
The intensity of light. The higher intensity, the higher rate.
The concentration of Carbon Dioxide. Higher concentration, higher rate.
Temperature. A certain range of temperature works the best. Too hot or too cold affects the work of enzymes, therefore affects the rate of photosynthesis.
Although photosynthesis is not something we as human beings would perform, it is extremely important to us and other animals, as well as the ecosystems. When we breathe, we inhale oxygen in the atmosphere released by plants through photosynthesis; when we eat vegetables, we get the energy produced by photosynthesis earlier in the plant.
Photosynthesis seems like a general thing that is far away from us, but when we really think about it, it is something that is closely related to us. And maybe next time breathing or eating vegetables, you will think about this word - Photosynthesis.
Written by: Benetta Wang
References:
Vidyasagar, Aparna. “What Is Photosynthesis?” Live Science, 15 Oct. 2018, www.livescience.com/51720-photosynthesis.html.
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