Why does photosynthesis produce O2 from CO2?

In summary, the conversation discusses the endothermic nature of the CO2 to O2 reaction in photosynthesis and the purpose of this reaction in providing energy for plant growth and survival. It is explained that while the process of photosynthesis may seem inefficient, it is necessary for plants to store energy from sunlight as chemical fuels. This stored energy is later used to power cellular functions through the exothermic reverse reaction. The conversation also mentions the importance of photosynthesis in the development of complex life forms on Earth and encourages further research on the topic.
  • #1
bbbl67
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My understanding is that the CO2 to O2 reaction is endothermic, so it takes more energy to be put in than you get back. So if plant life is attempting to get energy from photosynthesis, then why would it do an endothermic reaction which would take energy away from its cells?
 
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  • #2
They don't just need energy. To grow they need to make carbohydrates (sugars).

In the daytime they use sunlight to convert CO2 and water into carbohydrate and O2. Some O2 is released and some is used to split some of the carbohydrate to make energy. At night they absorb O2 to split the carbs.

Because not all of the carbohydrate produced is turned into energy there is a net excess of O2.
 
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  • #3
https://en.wikipedia.org/wiki/Photosynthetic_efficiency
If you look at the energy budgets of a plant, you find that plants have a net efficiency of ~3% - ~6%. The energy used goes into respiration (energy use) required for the photosynthetic process, growth, and reproduction. Plants store excess energy as lipids and starches, example: a carrot root. Farming is taking the excess plants have stored away and using it for human needs instead - heating, food, food preparation, and shelter.

So, if photosynthesis were not so very efficient, then it is likely that life on Earth would still be single celled anaerobic bacteria-like beasties.
 
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The point of photosynthesis is for plants and other photosynthetic organisms to store the energy of sunlight as chemical fuels that can later be burned to produce energy. Therefore, the reactions involved in photosynthesis should be endothermic so that they can take energy from an external source (the sun) and produce molecules with higher chemical potential energy (sugars). Overall, water + CO2 --> sugar + O2 is an endothermic reaction power by sunlight. This process later allows the plant to burn the sugars to produce energy that can be used to power cellular functions through the exothermic reverse reaction sugar + O2 --> water + CO2.
 
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  • #5
Good information so far, keep it coming folks.
 
  • #6
bbbl67 said:
So if plant life is attempting to get energy from photosynthesis, then why would it do an endothermic reaction which would take energy away from its cells?
The energy that runs the chemical reactions comes from sunlight.
O2 is released when CO2 is used to synthesise organic molecules.
bbbl67 said:
Good information so far, keep it coming folks.
Your question has been fully answered.
It is time you did some reading on the subject rather than wasting the time of others.
 
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  • #7
The OP question has been addressed. Thread closed.
 

Related to Why does photosynthesis produce O2 from CO2?

1. What is photosynthesis?

Photosynthesis is the process by which plants, algae, and some bacteria use energy from sunlight to convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2).

2. Why does photosynthesis produce oxygen from carbon dioxide?

Photosynthesis produces oxygen from carbon dioxide as a byproduct of the light-dependent reactions. During this process, light energy is used to split water molecules, releasing oxygen as a waste product.

3. How does photosynthesis convert carbon dioxide into oxygen?

Photosynthesis converts carbon dioxide into oxygen through a series of complex biochemical reactions. These reactions occur in two stages: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle).

4. What is the role of chlorophyll in photosynthesis?

Chlorophyll is a pigment found in the chloroplasts of plants and is responsible for absorbing light energy during photosynthesis. This energy is then used to power the conversion of carbon dioxide and water into glucose and oxygen.

5. Why is photosynthesis important to living organisms?

Photosynthesis is essential for sustaining life on Earth. It is the primary source of oxygen in the atmosphere, which is necessary for aerobic respiration in animals and humans. Additionally, photosynthesis produces glucose, which is used as a source of energy by all living organisms.

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