Time Frame

• Sugars like glucose are the end product of photosynthesis. Some of these sugars are used to synthesize other molecules the cell needs, but much of the sugar is used in cellular respiration. Aerobic (with oxygen) cellular respiration is divided into three stages: glycolysis, the Krebs cycle and oxidative phosphorylation via the electron transport chain and chemiosmotic coupling.
  
  

Features

• During glycolysis, a molecule of glucose is altered and broken up into two molecules of pyruvate. These pyruvates are fed into the Krebs cycle, which takes place inside the mitochondria of the cell and reduces electron carrier molecules that then donate high-energy electrons to the electron transport chain. The first two stages, glycolysis and the Krebs cycle, do not directly involve oxygen; oxygen acts as an electron acceptor during the final step.
  
  

Significance

• Although plants consume oxygen during cellular respiration, they release more oxygen through photosynthesis than they use up through respiration, so plants are net producers of oxygen. This balance is important for animals like humans, since we depend on oxygen in our atmosphere for our survival.