EnergyMetabolism/NutrientAndEnergy/BasicSummary

Nutrients have chemical energy, connecting atoms forming one molecule. When a nutrient enters a cell, so does its chemical energy. The cell takes out the chemical energy from the nutrient. This breaks down the nutrient, which becomes a degradation product. The cell activity,such as muscle contraction,consumes the taken-out energy. This is the overview of energy metabolism.

In the initial step of energy metabolism, oxygen (O₂) is NOT used. A small amount of energy is taken out, and a large amount of energy remains in the degradation product.

Oxygen also enters the cell,and in the next step of energy metabolism, oxygen IS used.A larger amount of energy is taken out, and the nutrient is broken down into many small degradation products, such as carbon dioxide (CO₂)and water(H₂O).Naturally,the cell can be active using such energy.

In summary, in the initial step of energy metabolism, oxygen is not used and a small amount of energy is taken out. In the next step, oxygen is used and a large amount of energy is taken out. The nutrient loses chemical energy, which had connected atoms to form one molecule, and is broken down into many small degradation products, such as carbon dioxide (CO₂) and water (H₂O) . The degradation products exit the cell.