Used Up:

* Oxygen (O2): This is the primary fuel for respiration. Cells use oxygen to break down glucose (a sugar) and release energy.

Produced:

* Carbon Dioxide (CO2): This is a waste product of respiration. It's produced when glucose is broken down and is exhaled from the body.

The Process:

Respiration is a complex process that occurs in the cells of all living organisms. It can be summarized as follows:

1. Intake of Oxygen: Organisms take in oxygen from the environment (through breathing in animals, or through leaves in plants).

2. Breakdown of Glucose: Oxygen is used to break down glucose, releasing energy in the form of ATP. This process is called cellular respiration.

3. Production of Carbon Dioxide: As a byproduct of this energy release, carbon dioxide is produced.

4. Exhalation of Carbon Dioxide: The carbon dioxide is released back into the environment (through exhaling or transpiration in plants).

In summary: Respiration uses oxygen and produces carbon dioxide.