Respiration--Do Plants Really Breathe?

Respiration--Do Plants Really Breathe?



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Respiration—Do Plants Really Breathe?  

When animals breathe, they use their lungs and diaphragm to draw in air. The lungs use this air to provide oxygen to the blood. The waste air, containing carbon dioxide, is exhaled. Is this the same thing as respiration?

Though you often see the words respiration and breathing used interchangeably, technically speaking respiration takes place on a cellular level. Respiration is the act of breaking the chemical bonds in food substances, releasing the energy contained within those bonds.

We often hear talk about how many calories we’ve "burned" during a workout at the gym. This burning is actually cellular respiration—we’re breaking the chemical bonds in stored food and using the energy released to run on that treadmill! (We also use the energy for all other body functions, such as digesting food, producing new cells, or even thinking.) And like other types of burning, oxygen is required for the process.

The chemical equation for cellular respiration is:

(CH2O) + O2    arrow.gif (56 bytes)     CO2 + H2O + energy

Carbohydrates plus oxygen yield carbon dioxide plus water plus energy.

Look closely at this equation and you’ll see that it’s essentially the equation for photosynthesis in reverse!

Back to our original question: do plants breathe? Plants don’t use muscles to draw in air—the exchange of gases is passive. So, technically, plants don’t breathe. But plants do respire. Like animals, they use oxygen in the process of breaking down carbohydrates, and use the energy released for basic metabolic functions such as repairing and replacing tissues, and building complex molecules like proteins and oils. During respiration, plants, like us, release carbon dioxide and water vapor.

Plants only photosynthesize in the presence of light, but they are continuously respiring, day and night. Even so, overall they release much more oxygen during photosynthesis than they consume during respiration!

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