Cells must perform thousands of different chemical reactions in order to survive.  These reactions are crucial to providing cells with energy.

Endergonic reactions:

-“energy in” require energy in order to proceed

– biological endergonic reactions produce molecules that store energy (ex. Glucose)

– Ex. Photosynthesis

Exergonic reatctions:

– “energy out” release energy

– biological exergonic reactions release useable energy from glucose to form ATP molecules

– Ex. Cellular respiration

ATP is the energy molecule of cells

Importance of ATP:

– cells are efficient in their energy use; ATP provides this efficiency

– ATP is a small molecule that releases small enough quantities to be useful to the cell

–  When a cell needs energy, it can use an appropriate number of small ATP molecules instead of wasting energy by spending a larger energy molecule (large carbohydrates)

Storage and Release of Energy in a molecule of ATP:

Release of energy – the bond between the 2nd and 3rd phosphate group is broken, energy

a phosphate are released (about 30 kJ) producing ADP

Storage of energy – ADP can be converted back to a molecule of ATP, a bond forms between the 2nd phosphate group and a new 3rd phosphate when energy is supplied

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