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What is cellular respiration?

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Quick answer

Cellular respiration is how cells release energy from food by breaking down glucose using oxygen, producing carbon dioxide, water, and usable energy (ATP). It's essentially the reverse of photosynthesis and runs in nearly all living cells. It mostly happens in the mitochondria, often called the cell's 'powerhouse.'.

Key things to understand

  1. It mostly happens in the mitochondria, often called the cell's 'powerhouse.'
  2. Inputs: glucose + oxygen. Outputs: carbon dioxide + water + ATP (energy).
  3. The overall reaction: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.
  4. It's why we breathe in oxygen and breathe out carbon dioxide.

People also ask

How is cellular respiration related to photosynthesis?
They're complementary: photosynthesis stores energy in glucose using CO₂ and water, while respiration releases that energy and gives back CO₂ and water.
What is ATP?
Adenosine triphosphate — the molecule cells use as their main energy currency to power their activities.
Can respiration happen without oxygen?
Yes, through anaerobic respiration or fermentation, but it releases far less energy than aerobic respiration with oxygen.