BSC 2010C How Cells make ATP Notes

C 7 How Cells make ATP:
Energy-Releasing Pathways

For cells to function (create new organic molecules, grow, reproduce)
They need a source of energy / For autotrophs, the source of energy is
sunlight (chapter 8) / For chemotrophs, the source of energy can be
organic molecules




Organic molecules (carbohydrates, lipids, proteins) can be converted into
ATP through a variety of different mechanisms
Cellular respiration and fermentation
• The processes by which cells convert the energy in an organic
molecule (glucose) into ATP through a series of redox reactions
Fermentation
The incomplete oxidation of glucose
• Not all the carbon in the glucose is converted into CO2
Generates less ATP than cell respiration
Does not require oxygen
Exergonic reactions – again, the energy in glucose is used to create ATP




Fermentation – incomplete oxidation of carbohydrates in the creation of ATP
• This process does not require molecular oxygen

, Cellular respiration
Involves the complete oxidation of glucose
Aerobic respiration (Requires molecular oxygen)
Anaerobic respiration (Does not require oxygen)
Exergonic reactions – overall the reaction releases energy (used to create
ATP)


cellular respiration
• A more efficient way to generate ATP from carbohydrates, lipids,
and proteins
• Cell respiration may require oxygen (aerobic cell respiration)
• Cell respiration may not require oxygen (anaerobic cell respiration)




In aerobic respiration:
One glucose is oxidized into six CO2
Six oxygen are reduced to six water molecules
Since glucose is oxidized, energy is released (used to create ATP)
C6H12O6 + 6O2 → 6CO2 + 6 H2O + energy


Three different processes
• Aerobic cell respiration – requires oxygen
• Anaerobic cell respiration – does not require oxygen
• Fermentation – does not require oxygen




2