* Carbon (C): This is the backbone of organic molecules like sugars, proteins, and fats.

* Oxygen (O): It's involved in both processes:

* Photosynthesis: Plants take in carbon dioxide (CO2) from the atmosphere, which contains oxygen, and use it to create sugars. They release oxygen as a byproduct.

* Cellular Respiration: Organisms take in oxygen from the atmosphere and use it to break down sugars, releasing carbon dioxide as a byproduct.

* Hydrogen (H): It's a component of water, which is used and produced in both processes.

* Energy: Photosynthesis captures light energy from the sun and stores it in chemical bonds of sugars. Cellular respiration releases this energy from the sugars, making it available for life processes.

Here's a simplified breakdown:

Photosynthesis:

* Takes in: Carbon dioxide (CO2), Water (H2O), Sunlight

* Produces: Glucose (C6H12O6), Oxygen (O2)

Cellular Respiration:

* Takes in: Glucose (C6H12O6), Oxygen (O2)

* Produces: Carbon dioxide (CO2), Water (H2O), Energy (ATP)

In essence, photosynthesis and cellular respiration are complementary processes. Photosynthesis uses light energy to build sugars, while cellular respiration breaks down sugars to release energy. Both processes are essential for life on Earth.